[libc] add syscall function

[michaelrj]

Summary

Add the syscall wrapper function and tests. It's implemented using a
macro to guarantee the minimum number of arguments.

[michaelrj]

rebase to include new additions

[sivachandra]

Can we call it syscall_impl instead of internal_syscall ?

libc/include/llvm-libc-macros/linux/unistd-macros.h

22

For better type checking, we should do something like this:

#define __syscall_helper(sysno, arg1, arg2, arg3, arg4, arg5, arg6, ...) \
    __llvm_libc_syscall((long)(sysno), (long)(arg1), (long)(arg2), (long)(arg3), \
                        (long)(arg4), (long)(arg5), (long)(arg6))
#define syscall(...) __syscall_helper(__VA_ARGS__, 1, 2, 3, 4, 5, 6, 7)

libc/src/unistd/linux/syscall.cpp

19

This need not be a vararg function - it can take exactly 7 arguments, the syscall number plus 6 other args.

libc/test/src/unistd/syscall_test.cpp

28

This is very misleading as there is no member named syscall in the namespace __llvm_libc. So, can you add a comment below line 22 explaining how the macro substitution helps in actually picking the namespace qualified __llvm_libc_syscall.

[michaelrj]

rename internal function, redo macro definition for type safety

[sivachandra]

libc/include/llvm-libc-macros/linux/unistd-macros.h

22

If you don't add a 7th argument below on line 25, will the macro on line 22 work when invoked like this: syscall(SYS_getpid)?

[michaelrj]

minor fix

libc/include/llvm-libc-macros/linux/unistd-macros.h

22

As far as I can tell it's fine in C++20, but possibly not in other versions (which is why my tests were passing), so I've added the 7th argument back as 0, to make it clearer that 1 matches to arg1, and so on.

libc/config/linux/x86_64/entrypoints.txt

set(TARGET_LIBC_ENTRYPOINTS
     libc.src.unistd.pread
     libc.src.unistd.pwrite
     libc.src.unistd.read
     libc.src.unistd.readlink
     libc.src.unistd.readlinkat
     libc.src.unistd.rmdir
     libc.src.unistd.symlink
     libc.src.unistd.symlinkat
+    libc.src.unistd.__llvm_libc_syscall
     libc.src.unistd.truncate
     libc.src.unistd.unlink
     libc.src.unistd.unlinkat
     libc.src.unistd.write
 )
 
 set(TARGET_LIBM_ENTRYPOINTS
     # fenv.h entrypoints

libc/include/llvm-libc-macros/linux/unistd-macros.h

 #define __LLVM_LIBC_MACROS_LINUX_UNISTD_MACROS_H
 
 // Values for mode argument to the access(...) function.
 #define F_OK 0
 #define X_OK 1
 #define W_OK 2
 #define R_OK 4
 
+// Macro to set up the call to the __llvm_libc_syscall function
+// This is to prevent the call from having fewer than 6 arguments, since six
+// arguments are always passed to the syscall. Unnecessary arguments are
+// ignored.
+#define __syscall_helper(sysno, arg1, arg2, arg3, arg4, arg5, arg6, ...)       \
+  __llvm_libc_syscall((long)(sysno), (long)(arg1), (long)(arg2), (long)(arg3), \
+                      (long)(arg4), (long)(arg5), (long)(arg6))
+#define syscall(...) __syscall_helper(__VA_ARGS__, 0, 1, 2, 3, 4, 5, 6)
+
 #endif // __LLVM_LIBC_MACROS_LINUX_UNISTD_MACROS_H

libc/loader/linux/aarch64/start.cpp

void init_tls(TLSDescriptor &tls_descriptor) {
   if (diff != 0)
     padding += (ALIGNMENT_MASK - diff) + 1;
 
   uintptr_t alloc_size = size_of_pointers + padding + app.tls.size;
 
   // We cannot call the mmap function here as the functions set errno on
   // failure. Since errno is implemented via a thread local variable, we cannot
   // use errno before TLS is setup.
-  long mmap_ret_val = __llvm_libc::syscall(MMAP_SYSCALL_NUMBER, nullptr,
-                                           alloc_size, PROT_READ | PROT_WRITE,
-                                           MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  long mmap_ret_val = __llvm_libc::syscall_impl(
+      MMAP_SYSCALL_NUMBER, nullptr, alloc_size, PROT_READ | PROT_WRITE,
   // We cannot check the return value with MAP_FAILED as that is the return
   // of the mmap function and not the mmap syscall.
   if (mmap_ret_val < 0 && static_cast<uintptr_t>(mmap_ret_val) > -app.pageSize)
-    __llvm_libc::syscall(SYS_exit, 1);
+    __llvm_libc::syscall_impl(SYS_exit, 1);
   uintptr_t thread_ptr = uintptr_t(reinterpret_cast<uintptr_t *>(mmap_ret_val));
   uintptr_t tls_addr = thread_ptr + size_of_pointers + padding;
   __llvm_libc::inline_memcpy(reinterpret_cast<char *>(tls_addr),
                              reinterpret_cast<const char *>(app.tls.address),
                              app.tls.init_size);
   tls_descriptor.size = alloc_size;
   tls_descriptor.addr = thread_ptr;
   tls_descriptor.tp = thread_ptr;
 }
 
 void cleanup_tls(uintptr_t addr, uintptr_t size) {
   if (size == 0)
     return;
-  __llvm_libc::syscall(SYS_munmap, addr, size);
+  __llvm_libc::syscall_impl(SYS_munmap, addr, size);
 }
 
 static void set_thread_ptr(uintptr_t val) { __arm_wsr64("tpidr_el0", val); }
 
 using InitCallback = void(int, char **, char **);
 using FiniCallback = void(void);
 
 extern "C" {

 
 // TODO: Would be nice to use the aux entry structure from elf.h when available.
 struct AuxEntry {
   uint64_t type;
   uint64_t value;
 };
 
 __attribute__((noinline)) static void do_start() {
-  auto tid = __llvm_libc::syscall(SYS_gettid);
+  auto tid = __llvm_libc::syscall_impl(SYS_gettid);
   if (tid <= 0)
-    __llvm_libc::syscall(SYS_exit, 1);
+    __llvm_libc::syscall_impl(SYS_exit, 1);
   __llvm_libc::main_thread_attrib.tid = tid;
 
   // After the argv array, is a 8-byte long NULL value before the array of env
   // values. The end of the env values is marked by another 8-byte long NULL
   // value. We step over it (the "+ 1" below) to get to the env values.
   uint64_t *env_ptr = app.args->argv + app.args->argc + 1;
   uint64_t *env_end_marker = env_ptr;
   app.envPtr = env_ptr;

libc/loader/linux/x86_64/start.cpp

void init_tls(TLSDescriptor &tls_descriptor) {
   // Per the x86_64 TLS ABI, the entry pointed to by the thread pointer is the
   // address of the TLS block. So, we add more size to accomodate this address
   // entry.
   uintptr_t tlsSizeWithAddr = tlsSize + sizeof(uintptr_t);
 
   // We cannot call the mmap function here as the functions set errno on
   // failure. Since errno is implemented via a thread local variable, we cannot
   // use errno before TLS is setup.
-  long mmapRetVal = __llvm_libc::syscall(
+  long mmapRetVal = __llvm_libc::syscall_impl(
       mmapSyscallNumber, nullptr, tlsSizeWithAddr, PROT_READ | PROT_WRITE,
       MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
   // We cannot check the return value with MAP_FAILED as that is the return
   // of the mmap function and not the mmap syscall.
   if (mmapRetVal < 0 && static_cast<uintptr_t>(mmapRetVal) > -app.pageSize)
-    __llvm_libc::syscall(SYS_exit, 1);
+    __llvm_libc::syscall_impl(SYS_exit, 1);
   uintptr_t *tlsAddr = reinterpret_cast<uintptr_t *>(mmapRetVal);
 
   // x86_64 TLS faces down from the thread pointer with the first entry
   // pointing to the address of the first real TLS byte.
   uintptr_t endPtr = reinterpret_cast<uintptr_t>(tlsAddr) + tlsSize;
   *reinterpret_cast<uintptr_t *>(endPtr) = endPtr;
 
   __llvm_libc::inline_memcpy(reinterpret_cast<char *>(tlsAddr),
                              reinterpret_cast<const char *>(app.tls.address),
                              app.tls.init_size);
 
   tls_descriptor = {tlsSizeWithAddr, uintptr_t(tlsAddr), endPtr};
   return;
 }
 
 void cleanup_tls(uintptr_t addr, uintptr_t size) {
   if (size == 0)
     return;
-  __llvm_libc::syscall(SYS_munmap, addr, size);
+  __llvm_libc::syscall_impl(SYS_munmap, addr, size);
 }
 
 // Sets the thread pointer to |val|. Returns true on success, false on failure.
 static bool set_thread_ptr(uintptr_t val) {
-  return __llvm_libc::syscall(SYS_arch_prctl, ARCH_SET_FS, val) == -1 ? false
-                                                                      : true;
+  return __llvm_libc::syscall_impl(SYS_arch_prctl, ARCH_SET_FS, val) == -1
+             ? false
 }
 
 using InitCallback = void(int, char **, char **);
 using FiniCallback = void(void);
 
 extern "C" {
 // These arrays are present in the .init_array and .fini_array sections.
 // The symbols are inserted by linker when it sees references to them.
extern "C" void _start() {
   // NOTE: Compiler attributes for alignment do not help here as the stack
   // pointer on entry to this _start function is controlled by the OS. In fact,
   // compilers can generate code assuming the alignment as required by the ABI.
   // If the stack pointers as setup by the OS are already aligned, then the
   // following code is a NOP.
   __asm__ __volatile__("andq $0xfffffffffffffff0, %%rsp\n\t" ::: "%rsp");
   __asm__ __volatile__("andq $0xfffffffffffffff0, %%rbp\n\t" ::: "%rbp");
 
-  auto tid = __llvm_libc::syscall(SYS_gettid);
+  auto tid = __llvm_libc::syscall_impl(SYS_gettid);
   if (tid <= 0)
-    __llvm_libc::syscall(SYS_exit, 1);
+    __llvm_libc::syscall_impl(SYS_exit, 1);
   __llvm_libc::main_thread_attrib.tid = tid;
 
   // After the argv array, is a 8-byte long NULL value before the array of env
   // values. The end of the env values is marked by another 8-byte long NULL
   // value. We step over it (the "+ 1" below) to get to the env values.
   uint64_t *env_ptr = app.args->argv + app.args->argc + 1;
   uint64_t *env_end_marker = env_ptr;
   app.envPtr = env_ptr;
for (uintptr_t i = 0; i < programHdrCount; ++i) {
     app.tls.size = phdr->p_memsz;
     app.tls.init_size = phdr->p_filesz;
     app.tls.align = phdr->p_align;
   }
 
   __llvm_libc::TLSDescriptor tls;
   __llvm_libc::init_tls(tls);
   if (tls.size != 0 && !__llvm_libc::set_thread_ptr(tls.tp))
-    __llvm_libc::syscall(SYS_exit, 1);
+    __llvm_libc::syscall_impl(SYS_exit, 1);
 
   __llvm_libc::self.attrib = &__llvm_libc::main_thread_attrib;
   __llvm_libc::main_thread_attrib.atexit_callback_mgr =
       __llvm_libc::internal::get_thread_atexit_callback_mgr();
 
   // We want the fini array callbacks to be run after other atexit
   // callbacks are run. So, we register them before running the init
   // array callbacks as they can potentially register their own atexit

libc/spec/posix.td

[
           [ArgSpec<ConstCharPtr>, ArgSpec<ConstCharPtr>]
         >,
         FunctionSpec<
           "symlinkat",
           RetValSpec<IntType>,
           [ArgSpec<IntType>, ArgSpec<ConstCharPtr>, ArgSpec<IntType>, ArgSpec<ConstCharPtr>]
         >,
         FunctionSpec<
+          "__llvm_libc_syscall",
+          RetValSpec<LongType>,
+          [ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>,ArgSpec<LongType>]
+        >,
+        FunctionSpec<
           "truncate",
           RetValSpec<IntType>,
           [ArgSpec<IntType>, ArgSpec<OffTType>]
         >,
         FunctionSpec<
           "unlink",
           RetValSpec<IntType>,
           [ArgSpec<ConstCharPtr>]

libc/src/__support/File/linux_dir.cpp

 #include <fcntl.h>       // For open flags
 #include <sys/syscall.h> // For syscall numbers
 
 namespace __llvm_libc {
 
 int platform_opendir(const char *name) {
   int open_flags = O_RDONLY | O_DIRECTORY | O_CLOEXEC;
 #ifdef SYS_open
-  int fd = __llvm_libc::syscall(SYS_open, name, open_flags);
+  int fd = __llvm_libc::syscall_impl(SYS_open, name, open_flags);
 #elif defined(SYS_openat)
-  int fd = __llvm_libc::syscall(SYS_openat, AT_FDCWD, name, open_flags);
+  int fd = __llvm_libc::syscall_impl(SYS_openat, AT_FDCWD, name, open_flags);
 #else
 #error                                                                         \
     "SYS_open and SYS_openat syscalls not available to perform an open operation."
 #endif
 
   if (fd < 0) {
     errno = -fd;
     return -1;
   }
   return fd;
 }
 
 size_t platform_fetch_dirents(int fd, cpp::span<uint8_t> buffer) {
   long size =
-      __llvm_libc::syscall(SYS_getdents, fd, buffer.data(), buffer.size());
+      __llvm_libc::syscall_impl(SYS_getdents, fd, buffer.data(), buffer.size());
   if (size < 0) {
     errno = -size;
     return 0;
   }
   return size;
 }
 
 bool platform_closedir(int fd) {
-  long ret = __llvm_libc::syscall(SYS_close, fd);
+  long ret = __llvm_libc::syscall_impl(SYS_close, fd);
   if (ret < 0) {
     errno = -ret;
     return false;
   }
   return true;
 }
 
 } // namespace __llvm_libc

libc/src/__support/File/linux_file.cpp

public:
 
   int get_fd() const { return fd; }
 };
 
 namespace {
 
 size_t write_func(File *f, const void *data, size_t size) {
   auto *lf = reinterpret_cast<LinuxFile *>(f);
-  long ret = __llvm_libc::syscall(SYS_write, lf->get_fd(), data, size);
+  long ret = __llvm_libc::syscall_impl(SYS_write, lf->get_fd(), data, size);
   if (ret < 0) {
     errno = -ret;
     return 0;
   }
   return ret;
 }
 
 size_t read_func(File *f, void *buf, size_t size) {
   auto *lf = reinterpret_cast<LinuxFile *>(f);
-  long ret = __llvm_libc::syscall(SYS_read, lf->get_fd(), buf, size);
+  long ret = __llvm_libc::syscall_impl(SYS_read, lf->get_fd(), buf, size);
   if (ret < 0) {
     errno = -ret;
     return 0;
   }
   return ret;
 }
 
 int seek_func(File *f, long offset, int whence) {
   auto *lf = reinterpret_cast<LinuxFile *>(f);
 #ifdef SYS_lseek
-  long ret = __llvm_libc::syscall(SYS_lseek, lf->get_fd(), offset, whence);
+  long ret = __llvm_libc::syscall_impl(SYS_lseek, lf->get_fd(), offset, whence);
 #elif defined(SYS__llseek)
   long result;
-  long ret = __llvm_libc::syscall(SYS__llseek, lf->get_fd(), offset >> 32,
+  long ret = __llvm_libc::syscall_impl(SYS__llseek, lf->get_fd(), offset >> 32,
                                        offset, &result, whence);
 #else
 #error "lseek and _llseek syscalls not available to perform a seek operation."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 int close_func(File *f) {
   auto *lf = reinterpret_cast<LinuxFile *>(f);
-  long ret = __llvm_libc::syscall(SYS_close, lf->get_fd());
+  long ret = __llvm_libc::syscall_impl(SYS_close, lf->get_fd());
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 int flush_func(File *f) {
   auto *lf = reinterpret_cast<LinuxFile *>(f);
-  long ret = __llvm_libc::syscall(SYS_fsync, lf->get_fd());
+  long ret = __llvm_libc::syscall_impl(SYS_fsync, lf->get_fd());
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // anonymous namespace
else
       open_flags |= O_RDONLY;
   }
 
   // File created will have 0666 permissions.
   constexpr long OPEN_MODE =
       S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH;
 
 #ifdef SYS_open
-  int fd = __llvm_libc::syscall(SYS_open, path, open_flags, OPEN_MODE);
+  int fd = __llvm_libc::syscall_impl(SYS_open, path, open_flags, OPEN_MODE);
 #elif defined(SYS_openat)
-  int fd =
-      __llvm_libc::syscall(SYS_openat, AT_FDCWD, path, open_flags, OPEN_MODE);
+  int fd = __llvm_libc::syscall_impl(SYS_openat, AT_FDCWD, path, open_flags,
+                                     OPEN_MODE);
 #else
 #error "SYS_open and SYS_openat syscalls not available to perform a file open."
 #endif
 
   if (fd < 0) {
     errno = -fd;
     return nullptr;
   }

libc/src/__support/OSUtil/linux/aarch64/syscall.h

 #define REGISTER_CONSTRAINT_5 REGISTER_CONSTRAINT_4, "r"(x4)
 #define REGISTER_CONSTRAINT_6 REGISTER_CONSTRAINT_5, "r"(x5)
 
 #define SYSCALL_INSTR(input_constraint)                                        \
   LIBC_INLINE_ASM("svc 0" : "=r"(x0) : input_constraint : "memory", "cc")
 
 namespace __llvm_libc {
 
-__attribute__((always_inline)) inline long syscall(long number) {
+__attribute__((always_inline)) inline long syscall_impl(long number) {
   REGISTER_DECL_0;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_0);
   return x0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1) {
+__attribute__((always_inline)) inline long syscall_impl(long number,
+                                                        long arg1) {
   REGISTER_DECL_1;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_1);
   return x0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1,
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
                                                         long arg2) {
   REGISTER_DECL_2;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_2);
   return x0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1,
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
                                                         long arg2, long arg3) {
   REGISTER_DECL_3;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_3);
   return x0;
 }
 
 __attribute__((always_inline)) inline long
-syscall(long number, long arg1, long arg2, long arg3, long arg4) {
+syscall_impl(long number, long arg1, long arg2, long arg3, long arg4) {
   REGISTER_DECL_4;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_4);
   return x0;
 }
 
-__attribute__((always_inline)) inline long
-syscall(long number, long arg1, long arg2, long arg3, long arg4, long arg5) {
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
+                                                        long arg2, long arg3,
+                                                        long arg4, long arg5) {
   REGISTER_DECL_5;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_5);
   return x0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1,
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
                                                         long arg2, long arg3,
                                                         long arg4, long arg5,
                                                         long arg6) {
   REGISTER_DECL_6;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_6);
   return x0;
 }
 
 } // namespace __llvm_libc
 
 #undef REGISTER_DECL_0

libc/src/__support/OSUtil/linux/arm/syscall.h

 #define REGISTER_CONSTRAINT_5 REGISTER_CONSTRAINT_4, "r"(r4)
 #define REGISTER_CONSTRAINT_6 REGISTER_CONSTRAINT_5, "r"(r5)
 
 #define SYSCALL_INSTR(input_constraint)                                        \
   LIBC_INLINE_ASM("svc 0" : "=r"(r0) : input_constraint : "memory", "cc")
 
 namespace __llvm_libc {
 
-__attribute__((always_inline)) inline long syscall(long number) {
+__attribute__((always_inline)) inline long syscall_impl(long number) {
   REGISTER_DECL_0;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_0);
   return r0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1) {
+__attribute__((always_inline)) inline long syscall_impl(long number,
+                                                        long arg1) {
   REGISTER_DECL_1;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_1);
   return r0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1,
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
                                                         long arg2) {
   REGISTER_DECL_2;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_2);
   return r0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1,
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
                                                         long arg2, long arg3) {
   REGISTER_DECL_3;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_3);
   return r0;
 }
 
 __attribute__((always_inline)) inline long
-syscall(long number, long arg1, long arg2, long arg3, long arg4) {
+syscall_impl(long number, long arg1, long arg2, long arg3, long arg4) {
   REGISTER_DECL_4;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_4);
   return r0;
 }
 
-__attribute__((always_inline)) inline long
-syscall(long number, long arg1, long arg2, long arg3, long arg4, long arg5) {
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
+                                                        long arg2, long arg3,
+                                                        long arg4, long arg5) {
   REGISTER_DECL_5;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_5);
   return r0;
 }
 
-__attribute__((always_inline)) inline long syscall(long number, long arg1,
+__attribute__((always_inline)) inline long syscall_impl(long number, long arg1,
                                                         long arg2, long arg3,
                                                         long arg4, long arg5,
                                                         long arg6) {
   REGISTER_DECL_6;
   SYSCALL_INSTR(REGISTER_CONSTRAINT_6);
   return r0;
 }
 
 } // namespace __llvm_libc
 
 #undef REGISTER_DECL_0

libc/src/__support/OSUtil/linux/io.h

 #include "src/string/string_utils.h"
 #include "syscall.h" // For internal syscall function.
 
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 static inline void write_to_stderr(const char *msg) {
-  __llvm_libc::syscall(SYS_write, 2 /* stderr */, msg,
+  __llvm_libc::syscall_impl(SYS_write, 2 /* stderr */, msg,
                             internal::string_length(msg));
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_IO_H

libc/src/__support/OSUtil/linux/quick_exit.h

 #include "syscall.h"             // For internal syscall function.
 
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 static inline void quick_exit(int status) {
   for (;;) {
-    __llvm_libc::syscall(SYS_exit_group, status);
-    __llvm_libc::syscall(SYS_exit, status);
+    __llvm_libc::syscall_impl(SYS_exit_group, status);
+    __llvm_libc::syscall_impl(SYS_exit, status);
   }
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_QUICK_EXIT_H

libc/src/__support/OSUtil/linux/syscall.h

 #include "aarch64/syscall.h"
 #elif defined(LLVM_LIBC_ARCH_ARM)
 #include "arm/syscall.h"
 #endif
 
 namespace __llvm_libc {
 
 template <typename... Ts>
-__attribute__((always_inline)) inline long syscall(long __number, Ts... ts) {
+__attribute__((always_inline)) inline long syscall_impl(long __number,
+                                                        Ts... ts) {
   static_assert(sizeof...(Ts) <= 6, "Too many arguments for syscall");
-  return syscall(__number, (long)ts...);
+  return syscall_impl(__number, (long)ts...);
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_SYSCALL_H

libc/src/__support/OSUtil/linux/x86_64/syscall.h

 #define LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_X86_64_SYSCALL_H
 
 #include "src/__support/common.h"
 
 #define SYSCALL_CLOBBER_LIST "rcx", "r11", "memory"
 
 namespace __llvm_libc {
 
-__attribute__((always_inline)) inline long syscall(long __number) {
+__attribute__((always_inline)) inline long syscall_impl(long __number) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
                   : "a"(__number)
                   : SYSCALL_CLOBBER_LIST);
   return retcode;
 }
 
-__attribute__((always_inline)) inline long syscall(long __number, long __arg1) {
+__attribute__((always_inline)) inline long syscall_impl(long __number,
+                                                        long __arg1) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
                   : "a"(__number), "D"(__arg1)
                   : SYSCALL_CLOBBER_LIST);
   return retcode;
 }
 
-__attribute__((always_inline)) inline long syscall(long __number, long __arg1,
-                                                   long __arg2) {
+__attribute__((always_inline)) inline long
+syscall_impl(long __number, long __arg1, long __arg2) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
                   : "a"(__number), "D"(__arg1), "S"(__arg2)
                   : SYSCALL_CLOBBER_LIST);
   return retcode;
 }
 
-__attribute__((always_inline)) inline long syscall(long __number, long __arg1,
-                                                   long __arg2, long __arg3) {
+__attribute__((always_inline)) inline long
+syscall_impl(long __number, long __arg1, long __arg2, long __arg3) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
                   : "a"(__number), "D"(__arg1), "S"(__arg2), "d"(__arg3)
                   : SYSCALL_CLOBBER_LIST);
   return retcode;
 }
 
 __attribute__((always_inline)) inline long
-syscall(long __number, long __arg1, long __arg2, long __arg3, long __arg4) {
+syscall_impl(long __number, long __arg1, long __arg2, long __arg3,
+             long __arg4) {
   long retcode;
   register long r10 __asm__("r10") = __arg4;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
                   : "a"(__number), "D"(__arg1), "S"(__arg2), "d"(__arg3),
                     "r"(r10)
                   : SYSCALL_CLOBBER_LIST);
   return retcode;
 }
 
-__attribute__((always_inline)) inline long syscall(long __number, long __arg1,
-                                                   long __arg2, long __arg3,
-                                                   long __arg4, long __arg5) {
+__attribute__((always_inline)) inline long
+syscall_impl(long __number, long __arg1, long __arg2, long __arg3, long __arg4,
+             long __arg5) {
   long retcode;
   register long r10 __asm__("r10") = __arg4;
   register long r8 __asm__("r8") = __arg5;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
                   : "a"(__number), "D"(__arg1), "S"(__arg2), "d"(__arg3),
                     "r"(r10), "r"(r8)
                   : SYSCALL_CLOBBER_LIST);
   return retcode;
 }
 
-__attribute__((always_inline)) inline long syscall(long __number, long __arg1,
-                                                   long __arg2, long __arg3,
-                                                   long __arg4, long __arg5,
-                                                   long __arg6) {
+__attribute__((always_inline)) inline long
+syscall_impl(long __number, long __arg1, long __arg2, long __arg3, long __arg4,
+             long __arg5, long __arg6) {
   long retcode;
   register long r10 __asm__("r10") = __arg4;
   register long r8 __asm__("r8") = __arg5;
   register long r9 __asm__("r9") = __arg6;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
                   : "a"(__number), "D"(__arg1), "S"(__arg2), "d"(__arg3),
                     "r"(r10), "r"(r8), "r"(r9)
                   : SYSCALL_CLOBBER_LIST);
   return retcode;
 }
 
 #undef SYSCALL_CLOBBER_LIST
-
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_X86_64_SYSCALL_H

libc/src/__support/threads/linux/callonce.cpp

int callonce(CallOnceFlag *flag, CallOnceCallback *func) {
   FutexWordType not_called = NOT_CALLED;
 
   // The call_once call can return only after the called function |func|
   // returns. So, we use futexes to synchronize calls with the same flag value.
   if (futex_word->compare_exchange_strong(not_called, START)) {
     func();
     auto status = futex_word->exchange(FINISH);
     if (status == WAITING) {
-      __llvm_libc::syscall(SYS_futex, &futex_word->val, FUTEX_WAKE_PRIVATE,
+      __llvm_libc::syscall_impl(SYS_futex, &futex_word->val, FUTEX_WAKE_PRIVATE,
                                 INT_MAX, // Wake all waiters.
                                 0, 0, 0);
     }
     return 0;
   }
 
   FutexWordType status = START;
   if (futex_word->compare_exchange_strong(status, WAITING) ||
       status == WAITING) {
-    __llvm_libc::syscall(SYS_futex, &futex_word->val, FUTEX_WAIT_PRIVATE,
-                         WAITING, // Block only if status is still |WAITING|.
-                         0, 0, 0);
+    __llvm_libc::syscall_impl(
+        SYS_futex, &futex_word->val, FUTEX_WAIT_PRIVATE,
   }
 
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/__support/threads/linux/mutex.h

while (true) {
       }
 
       switch (LockState(mutex_status)) {
       case LockState::Waiting:
         // If other threads are waiting already, then join them. Note that the
         // futex syscall will block if the futex data is still
         // `LockState::Waiting` (the 4th argument to the syscall function
         // below.)
-        __llvm_libc::syscall(SYS_futex, &futex_word.val, FUTEX_WAIT_PRIVATE,
+        __llvm_libc::syscall_impl(SYS_futex, &futex_word.val,
+                                  FUTEX_WAIT_PRIVATE,
                                   FutexWordType(LockState::Waiting), 0, 0, 0);
         was_waiting = true;
         // Once woken up/unblocked, try everything all over.
         continue;
       case LockState::Locked:
         // Mutex has been locked by another thread so set the status to
         // LockState::Waiting.
         if (futex_word.compare_exchange_strong(
                 locked_status, FutexWordType(LockState::Waiting))) {
           // If we are able to set the futex data to `LockState::Waiting`, then
           // we will wait for the futex to be woken up. Note again that the
           // following syscall will block only if the futex data is still
           // `LockState::Waiting`.
-          __llvm_libc::syscall(SYS_futex, &futex_word, FUTEX_WAIT_PRIVATE,
+          __llvm_libc::syscall_impl(SYS_futex, &futex_word, FUTEX_WAIT_PRIVATE,
                                     FutexWordType(LockState::Waiting), 0, 0, 0);
           was_waiting = true;
         }
         continue;
       case LockState::Free:
         // If it was LockState::Free, we shouldn't be here at all.
         return MutexError::BAD_LOCK_STATE;
       }
     }
   }
 
   MutexError unlock() {
     while (true) {
       FutexWordType mutex_status = FutexWordType(LockState::Waiting);
       if (futex_word.compare_exchange_strong(mutex_status,
                                              FutexWordType(LockState::Free))) {
         // If any thread is waiting to be woken up, then do it.
-        __llvm_libc::syscall(SYS_futex, &futex_word, FUTEX_WAKE_PRIVATE, 1, 0,
-                             0, 0);
+        __llvm_libc::syscall_impl(SYS_futex, &futex_word, FUTEX_WAKE_PRIVATE, 1,
+                                  0, 0, 0);
         return MutexError::NONE;
       }
 
       if (mutex_status == FutexWordType(LockState::Locked)) {
         // If nobody was waiting at this point, just free it.
         if (futex_word.compare_exchange_strong(mutex_status,
                                                FutexWordType(LockState::Free)))
           return MutexError::NONE;

libc/src/__support/threads/linux/thread.cpp

| CLONE_SYSVSEM // Share a single list of System V semaphore adjustment
                     // values
     | CLONE_PARENT_SETTID  // Set child thread ID in |ptid| of the parent.
     | CLONE_CHILD_CLEARTID // Let the kernel clear the tid address
                            // wake the joining thread.
     | CLONE_SETTLS;        // Setup the thread pointer of the new thread.
 
 static inline cpp::ErrorOr<void *> alloc_stack(size_t size) {
   long mmap_result =
-      __llvm_libc::syscall(MMAP_SYSCALL_NUMBER,
+      __llvm_libc::syscall_impl(MMAP_SYSCALL_NUMBER,
                                 0, // No special address
                                 size,
-                           PROT_READ | PROT_WRITE,      // Read and write stack
+                                PROT_READ | PROT_WRITE, // Read and write stack
                                 MAP_ANONYMOUS | MAP_PRIVATE, // Process private
                                 -1, // Not backed by any file
                                 0   // No offset
       );
   if (mmap_result < 0 && (uintptr_t(mmap_result) >= UINTPTR_MAX - size))
     return cpp::Error{int(-mmap_result)};
   return reinterpret_cast<void *>(mmap_result);
 }
 
 static inline void free_stack(void *stack, size_t size) {
-  __llvm_libc::syscall(SYS_munmap, stack, size);
+  __llvm_libc::syscall_impl(SYS_munmap, stack, size);
 }
 
 struct Thread;
 
 // We align the start args to 16-byte boundary as we adjust the allocated
 // stack memory with its size. We want the adjusted address to be at a
 // 16-byte boundary to satisfy the x86_64 and aarch64 ABI requirements.
 // If different architecture in future requires higher alignment, then we
int Thread::run(ThreadStyle style, ThreadRunner runner, void *arg, void *stack,
   attrib->platform_data = clear_tid;
 
   // The clone syscall takes arguments in an architecture specific order.
   // Also, we want the result of the syscall to be in a register as the child
   // thread gets a completely different stack after it is created. The stack
   // variables from this function will not be availalbe to the child thread.
 #ifdef LLVM_LIBC_ARCH_X86_64
   long register clone_result asm("rax");
-  clone_result = __llvm_libc::syscall(
+  clone_result = __llvm_libc::syscall_impl(
       SYS_clone, CLONE_SYSCALL_FLAGS, adjusted_stack,
       &attrib->tid,    // The address where the child tid is written
       &clear_tid->val, // The futex where the child thread status is signalled
       tls.tp           // The thread pointer value for the new thread.
   );
 #elif defined(LLVM_LIBC_ARCH_AARCH64)
   long register clone_result asm("x0");
-  clone_result = __llvm_libc::syscall(
+  clone_result = __llvm_libc::syscall_impl(
       SYS_clone, CLONE_SYSCALL_FLAGS, adjusted_stack,
       &attrib->tid,   // The address where the child tid is written
       tls.tp,         // The thread pointer value for the new thread.
       &clear_tid->val // The futex where the child thread status is signalled
   );
 #else
 #error "Unsupported architecture for the clone syscall."
 #endif
void Thread::wait() {
   // The kernel should set the value at the clear tid address to zero.
   // If not, it is a spurious wake and we should continue to wait on
   // the futex.
   auto *clear_tid =
       reinterpret_cast<cpp::Atomic<FutexWordType> *>(attrib->platform_data);
   while (clear_tid->load() != 0) {
     // We cannot do a FUTEX_WAIT_PRIVATE here as the kernel does a
     // FUTEX_WAKE and not a FUTEX_WAKE_PRIVATE.
-    __llvm_libc::syscall(SYS_futex, &clear_tid->val, FUTEX_WAIT,
+    __llvm_libc::syscall_impl(SYS_futex, &clear_tid->val, FUTEX_WAIT,
                               CLEAR_TID_VALUE, nullptr);
   }
 }
 
 bool Thread::operator==(const Thread &thread) const {
   return attrib->tid == thread.attrib->tid;
 }
 
 static constexpr cpp::string_view THREAD_NAME_PATH_PREFIX("/proc/self/task/");

 
 int Thread::set_name(const cpp::string_view &name) {
   if (name.size() >= NAME_SIZE_MAX)
     return ERANGE;
 
   if (*this == self) {
     // If we are setting the name of the current thread, then we can
     // use the syscall to set the name.
-    int retval = __llvm_libc::syscall(SYS_prctl, PR_SET_NAME, name.data());
+    int retval = __llvm_libc::syscall_impl(SYS_prctl, PR_SET_NAME, name.data());
     if (retval < 0)
       return -retval;
     else
       return 0;
   }
 
   char path_name_buffer[THREAD_NAME_PATH_SIZE];
   cpp::StringStream path_stream(path_name_buffer);
   construct_thread_name_file_path(path_stream, attrib->tid);
 #ifdef SYS_open
-  int fd = __llvm_libc::syscall(SYS_open, path_name_buffer, O_RDWR);
+  int fd = __llvm_libc::syscall_impl(SYS_open, path_name_buffer, O_RDWR);
 #else
-  int fd = __llvm_libc::syscall(SYS_openat, AT_FDCWD, path_name_buffer, O_RDWR);
+  int fd =
+      __llvm_libc::syscall_impl(SYS_openat, AT_FDCWD, path_name_buffer, O_RDWR);
 #endif
   if (fd < 0)
     return -fd;
 
-  int retval = __llvm_libc::syscall(SYS_write, fd, name.data(), name.size());
-  __llvm_libc::syscall(SYS_close, fd);
+  int retval =
+      __llvm_libc::syscall_impl(SYS_write, fd, name.data(), name.size());
+  __llvm_libc::syscall_impl(SYS_close, fd);
 
   if (retval < 0)
     return -retval;
   else if (retval != int(name.size()))
     return EIO;
   else
     return 0;
 }
 
 int Thread::get_name(cpp::StringStream &name) const {
   if (name.bufsize() < NAME_SIZE_MAX)
     return ERANGE;
 
   char name_buffer[NAME_SIZE_MAX];
 
   if (*this == self) {
     // If we are getting the name of the current thread, then we can
     // use the syscall to get the name.
-    int retval = __llvm_libc::syscall(SYS_prctl, PR_GET_NAME, name_buffer);
+    int retval = __llvm_libc::syscall_impl(SYS_prctl, PR_GET_NAME, name_buffer);
     if (retval < 0)
       return -retval;
     name << name_buffer;
     return 0;
   }
 
   char path_name_buffer[THREAD_NAME_PATH_SIZE];
   cpp::StringStream path_stream(path_name_buffer);
   construct_thread_name_file_path(path_stream, attrib->tid);
 #ifdef SYS_open
-  int fd = __llvm_libc::syscall(SYS_open, path_name_buffer, O_RDONLY);
+  int fd = __llvm_libc::syscall_impl(SYS_open, path_name_buffer, O_RDONLY);
 #else
-  int fd =
-      __llvm_libc::syscall(SYS_openat, AT_FDCWD, path_name_buffer, O_RDONLY);
+  int fd = __llvm_libc::syscall_impl(SYS_openat, AT_FDCWD, path_name_buffer,
+                                     O_RDONLY);
 #endif
   if (fd < 0)
     return -fd;
 
-  int retval = __llvm_libc::syscall(SYS_read, fd, name_buffer, NAME_SIZE_MAX);
-  __llvm_libc::syscall(SYS_close, fd);
+  int retval =
+      __llvm_libc::syscall_impl(SYS_read, fd, name_buffer, NAME_SIZE_MAX);
+  __llvm_libc::syscall_impl(SYS_close, fd);
   if (retval < 0)
     return -retval;
   if (retval == NAME_SIZE_MAX)
     return ERANGE;
   if (name_buffer[retval - 1] == '\n')
     name_buffer[retval - 1] = '\0';
   else
     name_buffer[retval] = '\0';
void thread_exit(ThreadReturnValue retval, ThreadStyle style) {
   uint32_t joinable_state = uint32_t(DetachState::JOINABLE);
   if (!attrib->detach_state.compare_exchange_strong(
           joinable_state, uint32_t(DetachState::EXITING))) {
     // Thread is detached so cleanup the resources.
     cleanup_thread_resources(attrib);
 
     // Set the CLEAR_TID address to nullptr to prevent the kernel
     // from signalling at a non-existent futex location.
-    __llvm_libc::syscall(SYS_set_tid_address, 0);
+    __llvm_libc::syscall_impl(SYS_set_tid_address, 0);
   }
 
   if (style == ThreadStyle::POSIX)
-    __llvm_libc::syscall(SYS_exit, retval.posix_retval);
+    __llvm_libc::syscall_impl(SYS_exit, retval.posix_retval);
   else
-    __llvm_libc::syscall(SYS_exit, retval.stdc_retval);
+    __llvm_libc::syscall_impl(SYS_exit, retval.stdc_retval);
 }
 
 } // namespace __llvm_libc

libc/src/fcntl/linux/creat.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, creat, (const char *path, int mode_flags)) {
 #ifdef SYS_open
-  int fd = __llvm_libc::syscall(SYS_open, path, O_CREAT | O_WRONLY | O_TRUNC,
-                                mode_flags);
+  int fd = __llvm_libc::syscall_impl(SYS_open, path,
+                                     O_CREAT | O_WRONLY | O_TRUNC, mode_flags);
 #else
-  int fd = __llvm_libc::syscall(SYS_openat, AT_FDCWD, path,
+  int fd = __llvm_libc::syscall_impl(SYS_openat, AT_FDCWD, path,
                                      O_CREAT | O_WRONLY | O_TRUNC, mode_flags);
 #endif
 
   if (fd > 0)
     return fd;
 
   errno = -fd;
   return -1;
 }
 
 } // namespace __llvm_libc

libc/src/fcntl/linux/open.cpp

LLVM_LIBC_FUNCTION(int, open, (const char *path, int flags, ...)) {
   if ((flags & O_CREAT) || (flags & O_TMPFILE) == O_TMPFILE) {
     va_list varargs;
     va_start(varargs, flags);
     mode_flags = va_arg(varargs, mode_t);
     va_end(varargs);
   }
 
 #ifdef SYS_open
-  int fd = __llvm_libc::syscall(SYS_open, path, flags, mode_flags);
+  int fd = __llvm_libc::syscall_impl(SYS_open, path, flags, mode_flags);
 #else
-  int fd = __llvm_libc::syscall(SYS_openat, AT_FDCWD, path, flags, mode_flags);
+  int fd =
+      __llvm_libc::syscall_impl(SYS_openat, AT_FDCWD, path, flags, mode_flags);
 #endif
   if (fd > 0)
     return fd;
 
   errno = -fd;
   return -1;
 }
 
 } // namespace __llvm_libc

libc/src/fcntl/linux/openat.cpp

LLVM_LIBC_FUNCTION(int, openat, (int dfd, const char *path, int flags, ...)) {
   // with O_TMPFILE
   if ((flags & O_CREAT) || (flags & O_TMPFILE) == O_TMPFILE) {
     va_list varargs;
     va_start(varargs, flags);
     mode_flags = va_arg(varargs, mode_t);
     va_end(varargs);
   }
 
-  int fd = __llvm_libc::syscall(SYS_openat, dfd, path, flags, mode_flags);
+  int fd = __llvm_libc::syscall_impl(SYS_openat, dfd, path, flags, mode_flags);
   if (fd > 0)
     return fd;
 
   errno = -fd;
   return -1;
 }
 
 } // namespace __llvm_libc

libc/src/sched/linux/sched_getaffinity.cpp

 #include <stdint.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, sched_getaffinity,
                    (pid_t tid, size_t cpuset_size, cpu_set_t *mask)) {
   long ret =
-      __llvm_libc::syscall(SYS_sched_getaffinity, tid, cpuset_size, mask);
+      __llvm_libc::syscall_impl(SYS_sched_getaffinity, tid, cpuset_size, mask);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   if (size_t(ret) < cpuset_size) {
     // This means that only |ret| bytes in |mask| have been set. We will have to
     // zero out the remaining bytes.
     auto *mask_bytes = reinterpret_cast<uint8_t *>(mask);
     for (size_t i = size_t(ret); i < cpuset_size; ++i)
       mask_bytes[i] = 0;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sched/linux/sched_setaffinity.cpp

 #include <sched.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, sched_setaffinity,
                    (pid_t tid, size_t cpuset_size, const cpu_set_t *mask)) {
   long ret =
-      __llvm_libc::syscall(SYS_sched_setaffinity, tid, cpuset_size, mask);
+      __llvm_libc::syscall_impl(SYS_sched_setaffinity, tid, cpuset_size, mask);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/signal/linux/__restore.cpp

 #include "src/__support/OSUtil/syscall.h"
 
 namespace __llvm_libc {
 
 extern "C" void __restore_rt()
     __attribute__((no_sanitize("all"),
                    hidden));
 
-extern "C" void __restore_rt() { __llvm_libc::syscall(SYS_rt_sigreturn); }
+extern "C" void __restore_rt() { __llvm_libc::syscall_impl(SYS_rt_sigreturn); }
 
 } // namespace __llvm_libc

libc/src/signal/linux/raise.cpp

 
 #include "src/__support/common.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, raise, (int sig)) {
   ::sigset_t sigset;
   block_all_signals(sigset);
-  long pid = __llvm_libc::syscall(SYS_getpid);
-  long tid = __llvm_libc::syscall(SYS_gettid);
-  int ret = __llvm_libc::syscall(SYS_tgkill, pid, tid, sig);
+  long pid = __llvm_libc::syscall_impl(SYS_getpid);
+  long tid = __llvm_libc::syscall_impl(SYS_gettid);
+  int ret = __llvm_libc::syscall_impl(SYS_tgkill, pid, tid, sig);
   restore_signals(sigset);
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/signal/linux/sigaction.cpp

if (libc_new) {
     kernel_new = *libc_new;
     if (!(kernel_new.sa_flags & SA_RESTORER)) {
       kernel_new.sa_flags |= SA_RESTORER;
       kernel_new.sa_restorer = __restore_rt;
     }
   }
 
   KernelSigaction kernel_old;
-  int ret = syscall(SYS_rt_sigaction, signal, libc_new ? &kernel_new : nullptr,
-                    libc_old ? &kernel_old : nullptr, sizeof(sigset_t));
+  int ret = __llvm_libc::syscall_impl(
+      SYS_rt_sigaction, signal, libc_new ? &kernel_new : nullptr,
   if (ret) {
     errno = -ret;
     return -1;
   }
 
   if (libc_old)
     *libc_old = kernel_old;
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/signal/linux/signal_utils.h

constexpr inline bool delete_signal(sigset_t &set, int signal) {
   size_t word = n / BITS_PER_SIGWORD;
   size_t bit = n % BITS_PER_SIGWORD;
   set.__signals[word] &= ~(1UL << bit);
   return true;
 }
 
 static inline int block_all_signals(sigset_t &set) {
   sigset_t full = full_set();
-  return __llvm_libc::syscall(SYS_rt_sigprocmask, SIG_BLOCK, &full, &set,
+  return __llvm_libc::syscall_impl(SYS_rt_sigprocmask, SIG_BLOCK, &full, &set,
                                    sizeof(sigset_t));
 }
 
 static inline int restore_signals(const sigset_t &set) {
-  return __llvm_libc::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &set, nullptr,
-                              sizeof(sigset_t));
+  return __llvm_libc::syscall_impl(SYS_rt_sigprocmask, SIG_SETMASK, &set,
+                                   nullptr, sizeof(sigset_t));
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_SIGNAL_LINUX_SIGNAL_UTILS_H

libc/src/signal/linux/sigprocmask.cpp

 #include <errno.h>
 #include <signal.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, sigprocmask,
                    (int how, const sigset_t *__restrict set,
                     sigset_t *__restrict oldset)) {
-  int ret = __llvm_libc::syscall(SYS_rt_sigprocmask, how, set, oldset,
+  int ret = __llvm_libc::syscall_impl(SYS_rt_sigprocmask, how, set, oldset,
                                       sizeof(sigset_t));
   if (!ret)
     return 0;
 
   errno = -ret;
   return -1;
 }
 
 } // namespace __llvm_libc

libc/src/stdio/linux/remove.cpp

 #include <fcntl.h>       // For AT_* macros.
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, remove, (const char *path)) {
   // We first try unlinking it as a file. If it is ia file, it will succeed. If
   // it fails with EISDIR, we will try unlinking it as a directory.
-  int ret = __llvm_libc::syscall(SYS_unlinkat, AT_FDCWD, path, 0);
+  int ret = __llvm_libc::syscall_impl(SYS_unlinkat, AT_FDCWD, path, 0);
   if (ret == -EISDIR)
-    ret = __llvm_libc::syscall(SYS_unlinkat, AT_FDCWD, path, AT_REMOVEDIR);
+    ret = __llvm_libc::syscall_impl(SYS_unlinkat, AT_FDCWD, path, AT_REMOVEDIR);
   if (ret >= 0)
     return 0;
   errno = -ret;
   return -1;
 }
 
 } // namespace __llvm_libc

libc/src/stdlib/linux/_Exit.cpp

 #include "src/__support/common.h"
 
 #include "src/stdlib/_Exit.h"
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(void, _Exit, (int status)) {
   for (;;) {
-    __llvm_libc::syscall(SYS_exit_group, status);
-    __llvm_libc::syscall(SYS_exit, status);
+    __llvm_libc::syscall_impl(SYS_exit_group, status);
+    __llvm_libc::syscall_impl(SYS_exit, status);
   }
 }
 
 } // namespace __llvm_libc

libc/src/sys/mman/linux/madvise.cpp

 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 // This function is currently linux only. It has to be refactored suitably if
 // madvise is to be supported on non-linux operating systems also.
 LLVM_LIBC_FUNCTION(int, madvise, (void *addr, size_t size, int advice)) {
-  long ret_val = __llvm_libc::syscall(SYS_madvise, reinterpret_cast<long>(addr),
-                                      size, advice);
+  long ret_val = __llvm_libc::syscall_impl(
+      SYS_madvise, reinterpret_cast<long>(addr), size, advice);
 
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
   if (ret_val < 0) {
     errno = -ret_val;
     return -1;
   }
 
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/mman/linux/mmap.cpp

#ifdef SYS_mmap2
   long syscall_number = SYS_mmap2;
 #elif SYS_mmap
   long syscall_number = SYS_mmap;
 #else
 #error "Target platform does not have SYS_mmap or SYS_mmap2 defined"
 #endif
 
   long ret_val =
-      __llvm_libc::syscall(syscall_number, reinterpret_cast<long>(addr), size,
-                           prot, flags, fd, offset);
+      __llvm_libc::syscall_impl(syscall_number, reinterpret_cast<long>(addr),
+                                size, prot, flags, fd, offset);
 
   // The mmap/mmap2 syscalls return negative values on error. These negative
   // values are actually the negative values of the error codes. So, fix them
   // up in case an error code is detected.
   //
   // A point to keep in mind for the fix up is that a negative return value
   // from the syscall can also be an error-free value returned by the syscall.
   // However, since a valid return address cannot be within the last page, a

libc/src/sys/mman/linux/mprotect.cpp

 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 // This function is currently linux only. It has to be refactored suitably if
 // mprotect is to be supported on non-linux operating systems also.
 LLVM_LIBC_FUNCTION(int, mprotect, (void *addr, size_t size, int prot)) {
-  long ret_val = __llvm_libc::syscall(SYS_mprotect,
-                                      reinterpret_cast<long>(addr), size, prot);
+  long ret_val = __llvm_libc::syscall_impl(
+      SYS_mprotect, reinterpret_cast<long>(addr), size, prot);
 
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
   if (ret_val < 0) {
     errno = -ret_val;
     return -1;
   }
 
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/mman/linux/munmap.cpp

 #include <sys/syscall.h>          // For syscall numbers.
 
 namespace __llvm_libc {
 
 // This function is currently linux only. It has to be refactored suitably if
 // mmap is to be supported on non-linux operating systems also.
 LLVM_LIBC_FUNCTION(int, munmap, (void *addr, size_t size)) {
   long ret_val =
-      __llvm_libc::syscall(SYS_munmap, reinterpret_cast<long>(addr), size);
+      __llvm_libc::syscall_impl(SYS_munmap, reinterpret_cast<long>(addr), size);
 
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
   if (ret_val < 0) {
     errno = -ret_val;
     return -1;
   }
 
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/mman/linux/posix_madvise.cpp

 // This function is currently linux only. It has to be refactored suitably if
 // posix_madvise is to be supported on non-linux operating systems also.
 LLVM_LIBC_FUNCTION(int, posix_madvise, (void *addr, size_t size, int advice)) {
   // POSIX_MADV_DONTNEED does nothing because the default MADV_DONTNEED may
   // cause data loss, which the posix madvise does not allow.
   if (advice == POSIX_MADV_DONTNEED) {
     return 0;
   }
-  long ret_val = __llvm_libc::syscall(SYS_madvise, reinterpret_cast<long>(addr),
-                                      size, advice);
+  long ret_val = __llvm_libc::syscall_impl(
+      SYS_madvise, reinterpret_cast<long>(addr), size, advice);
   return ret_val < 0 ? -ret_val : 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/resource/linux/getrlimit.cpp

 
 #include <errno.h>
 #include <sys/resource.h> // For struct rlimit
 #include <sys/syscall.h>  // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, getrlimit, (int res, struct rlimit *limits)) {
-  long ret = __llvm_libc::syscall(SYS_prlimit64, 0, res, nullptr, limits);
+  long ret = __llvm_libc::syscall_impl(SYS_prlimit64, 0, res, nullptr, limits);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/resource/linux/setrlimit.cpp

 
 #include <errno.h>
 #include <sys/resource.h> // For struct rlimit
 #include <sys/syscall.h>  // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, setrlimit, (int res, const struct rlimit *limits)) {
-  long ret = __llvm_libc::syscall(SYS_prlimit64, 0, res, limits, nullptr);
+  long ret = __llvm_libc::syscall_impl(SYS_prlimit64, 0, res, limits, nullptr);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/sendfile/linux/sendfile.cpp

 #include <errno.h>
 #include <sys/sendfile.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(ssize_t, sendfile,
                    (int out_fd, int in_fd, off_t *offset, size_t count)) {
-  long ret = __llvm_libc::syscall(SYS_sendfile, in_fd, out_fd, offset, count);
+  long ret =
+      __llvm_libc::syscall_impl(SYS_sendfile, in_fd, out_fd, offset, count);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/sys/stat/linux/chmod.cpp

 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, chmod, (const char *path, mode_t mode)) {
 #ifdef SYS_chmod
-  long ret = __llvm_libc::syscall(SYS_chmod, path, mode);
+  long ret = __llvm_libc::syscall_impl(SYS_chmod, path, mode);
 #elif defined(SYS_fchmodat)
-  long ret = __llvm_libc::syscall(SYS_fchmodat, AT_FDCWD, path, mode);
+  long ret = __llvm_libc::syscall_impl(SYS_fchmodat, AT_FDCWD, path, mode);
 #else
 #error "chmod and chmodat syscalls not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/stat/linux/fchmod.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, fchmod, (int fd, mode_t mode)) {
-  long ret = __llvm_libc::syscall(SYS_fchmod, fd, mode);
+  long ret = __llvm_libc::syscall_impl(SYS_fchmod, fd, mode);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/stat/linux/fchmodat.cpp

 #include <errno.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, fchmodat,
                    (int dirfd, const char *path, mode_t mode, int flags)) {
-  long ret = __llvm_libc::syscall(SYS_fchmodat, dirfd, path, mode, flags);
+  long ret = __llvm_libc::syscall_impl(SYS_fchmodat, dirfd, path, mode, flags);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/stat/linux/kernel_statx.h

 } // Anonymous namespace
 
 namespace __llvm_libc {
 
 inline int statx(int dirfd, const char *__restrict path, int flags,
                  struct stat *__restrict statbuf) {
   // We make a statx syscall and copy out the result into the |statbuf|.
   ::statx_buf xbuf;
-  long ret =
-      syscall(SYS_statx, dirfd, path, flags, ::STATX_BASIC_STATS_MASK, &xbuf);
+  long ret = __llvm_libc::syscall_impl(SYS_statx, dirfd, path, flags,
+                                       ::STATX_BASIC_STATS_MASK, &xbuf);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
 
   statbuf->st_dev = MKDEV(xbuf.stx_dev_major, xbuf.stx_dev_minor);
   statbuf->st_ino = xbuf.stx_ino;
   statbuf->st_mode = xbuf.stx_mode;

libc/src/sys/stat/linux/mkdir.cpp

 #include <fcntl.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, mkdir, (const char *path, mode_t mode)) {
 #ifdef SYS_mkdir
-  long ret = __llvm_libc::syscall(SYS_mkdir, path, mode);
+  long ret = __llvm_libc::syscall_impl(SYS_mkdir, path, mode);
 #elif defined(SYS_mkdirat)
-  long ret = __llvm_libc::syscall(SYS_mkdirat, AT_FDCWD, path, mode);
+  long ret = __llvm_libc::syscall_impl(SYS_mkdirat, AT_FDCWD, path, mode);
 #else
 #error "mkdir and mkdirat syscalls not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/stat/linux/mkdirat.cpp

 #include <errno.h>
 #include <sys/stat.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, mkdirat, (int dfd, const char *path, mode_t mode)) {
 #ifdef SYS_mkdirat
-  long ret = __llvm_libc::syscall(SYS_mkdirat, dfd, path, mode);
+  long ret = __llvm_libc::syscall_impl(SYS_mkdirat, dfd, path, mode);
 #else
 #error "mkdirat syscalls not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/sys/utsname/linux/uname.cpp

 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 #include <sys/utsname.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, uname, (struct utsname * name)) {
-  long ret = __llvm_libc::syscall(SYS_uname, name);
+  long ret = __llvm_libc::syscall_impl(SYS_uname, name);
 
   if (ret >= 0)
     return 1;
   errno = -ret;
   return -1;
 }
 
 } // namespace __llvm_libc

libc/src/threads/linux/CndVar.h

CndWaiter waiter;
           waitq_front = nullptr;
         else
           waitq_back->next = nullptr;
 
         return thrd_error;
       }
     }
 
-    __llvm_libc::syscall(SYS_futex, &waiter.futex_word.val, FUTEX_WAIT,
+    __llvm_libc::syscall_impl(SYS_futex, &waiter.futex_word.val, FUTEX_WAIT,
                               WS_Waiting, 0, 0, 0);
 
     // At this point, if locking |m| fails, we can simply return as the
     // queued up waiter would have been removed from the queue.
     auto err = m->lock();
     return err == MutexError::NONE ? thrd_success : thrd_error;
   }
 
   int notify_one() {
     // We don't use an RAII locker in this method as we want to unlock
     // |qmtx| and signal the waiter using a single FUTEX_WAKE_OP signal.
     qmtx.lock();
     if (waitq_front == nullptr) {
       qmtx.unlock();
       return thrd_success;
     }
 
     CndWaiter *first = waitq_front;
     waitq_front = waitq_front->next;
     if (waitq_front == nullptr)
       waitq_back = nullptr;
 
     qmtx.futex_word = FutexWordType(Mutex::LockState::Free);
 
-    __llvm_libc::syscall(
+    __llvm_libc::syscall_impl(
         SYS_futex, &qmtx.futex_word.val, FUTEX_WAKE_OP, 1, 1,
         &first->futex_word.val,
         FUTEX_OP(FUTEX_OP_SET, WS_Signalled, FUTEX_OP_CMP_EQ, WS_Waiting));
     return thrd_success;
   }
 
   int broadcast() {
     MutexLock ml(&qmtx);
     uint32_t dummy_futex_word;
     CndWaiter *waiter = waitq_front;
     waitq_front = waitq_back = nullptr;
     while (waiter != nullptr) {
       // FUTEX_WAKE_OP is used instead of just FUTEX_WAKE as it allows us to
       // atomically update the waiter status to WS_Signalled before waking
       // up the waiter. A dummy location is used for the other futex of
       // FUTEX_WAKE_OP.
-      __llvm_libc::syscall(
+      __llvm_libc::syscall_impl(
           SYS_futex, &dummy_futex_word, FUTEX_WAKE_OP, 1, 1,
           &waiter->futex_word.val,
           FUTEX_OP(FUTEX_OP_SET, WS_Signalled, FUTEX_OP_CMP_EQ, WS_Waiting));
       waiter = waiter->next;
     }
     return thrd_success;
   }
 };

libc/src/threads/linux/call_once.cpp

LLVM_LIBC_FUNCTION(void, call_once,
   //
   // What this means is that, the call_once call can return only after
   // the called function |func| returns. So, we use futexes to synchronize
   // calls with the same flag value.
   if (futex_word->compare_exchange_strong(not_called, START)) {
     func();
     auto status = futex_word->exchange(FINISH);
     if (status == WAITING) {
-      __llvm_libc::syscall(SYS_futex, &futex_word->val, FUTEX_WAKE_PRIVATE,
+      __llvm_libc::syscall_impl(SYS_futex, &futex_word->val, FUTEX_WAKE_PRIVATE,
                                 INT_MAX, // Wake all waiters.
                                 0, 0, 0);
     }
     return;
   }
 
   FutexWordType status = START;
   if (futex_word->compare_exchange_strong(status, WAITING) ||
       status == WAITING) {
-    __llvm_libc::syscall(SYS_futex, &futex_word->val, FUTEX_WAIT_PRIVATE,
-                         WAITING, // Block only if status is still |WAITING|.
-                         0, 0, 0);
+    __llvm_libc::syscall_impl(
+        SYS_futex, &futex_word->val, FUTEX_WAIT_PRIVATE,
   }
 }
 
 } // namespace __llvm_libc

libc/src/time/clock_gettime.cpp

 #include <sys/syscall.h> // For syscall numbers.
 #include <time.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, clock_gettime,
                    (clockid_t clockid, struct timespec *tp)) {
   long ret_val =
-      __llvm_libc::syscall(SYS_clock_gettime, static_cast<long>(clockid),
+      __llvm_libc::syscall_impl(SYS_clock_gettime, static_cast<long>(clockid),
                                 reinterpret_cast<long>(tp));
   // A negative return value indicates an error with the magnitude of the
   // value being the error code.
   if (ret_val < 0) {
     errno = -ret_val;
     return -1;
   }
 
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/time/nanosleep.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, nanosleep,
                    (const struct timespec *req, struct timespec *rem)) {
-  int ret = __llvm_libc::syscall(SYS_nanosleep, req, rem);
+  int ret = __llvm_libc::syscall_impl(SYS_nanosleep, req, rem);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/CMakeLists.txt

 add_entrypoint_object(
   symlinkat
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.symlinkat
 )
 
 add_entrypoint_object(
+  __llvm_libc_syscall
+  ALIAS
+  DEPENDS
+    .${LIBC_TARGET_OS}.__llvm_libc_syscall
+)
+
+add_entrypoint_object(
   truncate
   ALIAS
   DEPENDS
     .${LIBC_TARGET_OS}.truncate
 )
 
 add_entrypoint_object(
   unlink

libc/src/unistd/linux/CMakeLists.txt

DEPENDS
     libc.include.fcntl
     libc.include.unistd
     libc.include.sys_syscall
     libc.src.__support.OSUtil.osutil
     libc.src.errno.errno
 )
 
 add_entrypoint_object(
+  __llvm_libc_syscall
+  SRCS
+    syscall.cpp
+  HDRS
+    ../syscall.h
+  DEPENDS
+    libc.include.unistd
+    libc.src.__support.OSUtil.osutil
+    libc.src.errno.errno
+)
+
+add_entrypoint_object(
   truncate
   SRCS
     truncate.cpp
   HDRS
     ../truncate.h
   DEPENDS
     libc.include.unistd
     libc.include.sys_syscall

libc/src/unistd/linux/access.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, access, (const char *path, int mode)) {
 #ifdef SYS_access
-  long ret = __llvm_libc::syscall(SYS_access, path, mode);
+  long ret = __llvm_libc::syscall_impl(SYS_access, path, mode);
 #elif defined(SYS_faccessat)
-  long ret = __llvm_libc::syscall(SYS_faccessat, AT_FDCWD, path, mode, 0);
+  long ret = __llvm_libc::syscall_impl(SYS_faccessat, AT_FDCWD, path, mode, 0);
 #else
 #error "access syscalls not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/chdir.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, chdir, (const char *path)) {
-  long ret = __llvm_libc::syscall(SYS_chdir, path);
+  long ret = __llvm_libc::syscall_impl(SYS_chdir, path);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/close.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, close, (int fd)) {
-  long ret = __llvm_libc::syscall(SYS_close, fd);
+  long ret = __llvm_libc::syscall_impl(SYS_close, fd);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/dup.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, dup, (int fd)) {
-  long ret = __llvm_libc::syscall(SYS_dup, fd);
+  long ret = __llvm_libc::syscall_impl(SYS_dup, fd);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/dup2.cpp

 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, dup2, (int oldfd, int newfd)) {
 #ifdef SYS_dup2
   // If dup2 syscall is available, we make use of directly.
-  long ret = __llvm_libc::syscall(SYS_dup2, oldfd, newfd);
+  long ret = __llvm_libc::syscall_impl(SYS_dup2, oldfd, newfd);
 #elif defined(SYS_dup3)
   // If dup2 syscall is not available, we try using the dup3 syscall. However,
   // dup3 fails if oldfd is the same as newfd. So, we handle that case
   // separately before making the dup3 syscall.
   if (oldfd == newfd) {
     // Check if oldfd is actually a valid file descriptor.
-    long ret = __llvm_libc::syscall(SYS_fcntl, oldfd, F_GETFD);
+    long ret = __llvm_libc::syscall_impl(SYS_fcntl, oldfd, F_GETFD);
     if (ret >= 0)
       return oldfd;
     errno = -ret;
     return -1;
   }
-  long ret = __llvm_libc::syscall(SYS_dup3, oldfd, newfd, 0);
+  long ret = __llvm_libc::syscall_impl(SYS_dup3, oldfd, newfd, 0);
 #else
 #error "SYS_dup2 and SYS_dup3 not available for the target."
 #endif
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/dup3.cpp

 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, dup3, (int oldfd, int newfd, int flags)) {
   // If dup2 syscall is available, we make use of directly.
-  long ret = __llvm_libc::syscall(SYS_dup3, oldfd, newfd, flags);
+  long ret = __llvm_libc::syscall_impl(SYS_dup3, oldfd, newfd, flags);
   if (ret >= 0)
     return ret;
   errno = -ret;
   return -1;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/fchdir.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, fchdir, (int fd)) {
-  long ret = __llvm_libc::syscall(SYS_fchdir, fd);
+  long ret = __llvm_libc::syscall_impl(SYS_fchdir, fd);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/fsync.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, fsync, (int fd)) {
-  long ret = __llvm_libc::syscall(SYS_fsync, fd);
+  long ret = __llvm_libc::syscall_impl(SYS_fsync, fd);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/ftruncate.cpp

 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 #include <unistd.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, ftruncate, (int fd, off_t len)) {
-  int ret = __llvm_libc::syscall(SYS_ftruncate, fd, len);
+  int ret = __llvm_libc::syscall_impl(SYS_ftruncate, fd, len);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/geteuid.cpp

 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(uid_t, geteuid, ()) {
-  return __llvm_libc::syscall(SYS_geteuid);
+  return __llvm_libc::syscall_impl(SYS_geteuid);
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/getpid.cpp

 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(pid_t, getpid, ()) {
-  return __llvm_libc::syscall(SYS_getpid);
+  return __llvm_libc::syscall_impl(SYS_getpid);
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/getppid.cpp

 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(pid_t, getppid, ()) {
-  return __llvm_libc::syscall(SYS_getppid);
+  return __llvm_libc::syscall_impl(SYS_getppid);
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/getuid.cpp

 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(uid_t, getuid, ()) {
-  return __llvm_libc::syscall(SYS_getuid);
+  return __llvm_libc::syscall_impl(SYS_getuid);
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/link.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, link, (const char *path1, const char *path2)) {
 #ifdef SYS_link
-  long ret = __llvm_libc::syscall(SYS_link, path1, path2);
+  long ret = __llvm_libc::syscall_impl(SYS_link, path1, path2);
 #elif defined(SYS_linkat)
-  long ret =
-      __llvm_libc::syscall(SYS_linkat, AT_FDCWD, path1, AT_FDCWD, path2, 0);
+  long ret = __llvm_libc::syscall_impl(SYS_linkat, AT_FDCWD, path1, AT_FDCWD,
+                                       path2, 0);
 #else
 #error "SYS_link or SYS_linkat not available."
 #endif
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/linkat.cpp

 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, linkat,
                    (int fd1, const char *path1, int fd2, const char *path2,
                     int flags)) {
-  long ret = __llvm_libc::syscall(SYS_linkat, fd1, path1, fd2, path2, flags);
+  long ret =
+      __llvm_libc::syscall_impl(SYS_linkat, fd1, path1, fd2, path2, flags);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/lseek.cpp

 #include <sys/syscall.h> // For syscall numbers.
 #include <unistd.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(off_t, lseek, (int fd, off_t offset, int whence)) {
   off_t result;
 #ifdef SYS_lseek
-  long ret = __llvm_libc::syscall(SYS_lseek, fd, offset, whence);
+  long ret = __llvm_libc::syscall_impl(SYS_lseek, fd, offset, whence);
   result = ret;
 #elif defined(SYS__llseek)
-  long ret = __llvm_libc::syscall(SYS__llseek, fd, offset >> 32, offset,
+  long ret = __llvm_libc::syscall_impl(SYS__llseek, fd, offset >> 32, offset,
                                        &result, whence);
 #else
 #error "lseek and _llseek syscalls not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return result;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/pread.cpp

 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(ssize_t, pread,
                    (int fd, void *buf, size_t count, off_t offset)) {
-  long ret = __llvm_libc::syscall(SYS_pread64, fd, buf, count, offset);
+  long ret = __llvm_libc::syscall_impl(SYS_pread64, fd, buf, count, offset);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/pwrite.cpp

 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(ssize_t, pwrite,
                    (int fd, const void *buf, size_t count, off_t offset)) {
-  long ret = __llvm_libc::syscall(SYS_pwrite64, fd, buf, count, offset);
+  long ret = __llvm_libc::syscall_impl(SYS_pwrite64, fd, buf, count, offset);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/read.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(ssize_t, read, (int fd, void *buf, size_t count)) {
-  long ret = __llvm_libc::syscall(SYS_read, fd, buf, count);
+  long ret = __llvm_libc::syscall_impl(SYS_read, fd, buf, count);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/readlink.cpp

 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(ssize_t, readlink,
                    (const char *__restrict path, char *__restrict buf,
                     size_t bufsize)) {
 #ifdef SYS_readlink
-  ssize_t ret = __llvm_libc::syscall(SYS_readlink, path, buf, bufsize);
+  ssize_t ret = __llvm_libc::syscall_impl(SYS_readlink, path, buf, bufsize);
 #elif defined(SYS_readlinkat)
   ssize_t ret =
-      __llvm_libc::syscall(SYS_readlinkat, AT_FDCWD, path, buf, bufsize);
+      __llvm_libc::syscall_impl(SYS_readlinkat, AT_FDCWD, path, buf, bufsize);
 #else
 #error "SYS_readlink or SYS_readlinkat not available."
 #endif
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/readlinkat.cpp

 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(ssize_t, readlinkat,
                    (int fd, const char *__restrict path, char *__restrict buf,
                     size_t bufsize)) {
-  ssize_t ret = __llvm_libc::syscall(SYS_readlinkat, fd, path, buf, bufsize);
+  ssize_t ret =
+      __llvm_libc::syscall_impl(SYS_readlinkat, fd, path, buf, bufsize);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/rmdir.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, rmdir, (const char *path)) {
 #ifdef SYS_rmdir
-  long ret = __llvm_libc::syscall(SYS_rmdir, path);
+  long ret = __llvm_libc::syscall_impl(SYS_rmdir, path);
 #elif defined(SYS_unlinkat)
-  long ret = __llvm_libc::syscall(SYS_unlinkat, AT_FDCWD, path, AT_REMOVEDIR);
+  long ret =
+      __llvm_libc::syscall_impl(SYS_unlinkat, AT_FDCWD, path, AT_REMOVEDIR);
 #else
 #error "rmdir and unlinkat syscalls not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/symlink.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, symlink, (const char *path1, const char *path2)) {
 #ifdef SYS_symlink
-  long ret = __llvm_libc::syscall(SYS_symlink, path1, path2);
+  long ret = __llvm_libc::syscall_impl(SYS_symlink, path1, path2);
 #elif defined(SYS_symlinkat)
-  long ret = __llvm_libc::syscall(SYS_symlinkat, path1, AT_FDCWD, path2);
+  long ret = __llvm_libc::syscall_impl(SYS_symlinkat, path1, AT_FDCWD, path2);
 #else
 #error "SYS_symlink or SYS_symlinkat not available."
 #endif
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/symlinkat.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, symlinkat,
                    (const char *path1, int fd, const char *path2)) {
-  long ret = __llvm_libc::syscall(SYS_symlinkat, path1, fd, path2);
+  long ret = __llvm_libc::syscall_impl(SYS_symlinkat, path1, fd, path2);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/syscall.cpp

-//===-- Linux implementation of link --------------------------------------===//
+//===-- Linux implementation of syscall -----------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-#include "src/unistd/link.h"
+#include "src/unistd/syscall.h"
 
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 
 #include <errno.h>
-#include <fcntl.h>
-#include <sys/syscall.h> // For syscall numbers.
+#include <stdarg.h>
 
 namespace __llvm_libc {
 
-LLVM_LIBC_FUNCTION(int, link, (const char *path1, const char *path2)) {
-#ifdef SYS_link
-  long ret = __llvm_libc::syscall(SYS_link, path1, path2);
-#elif defined(SYS_linkat)
+LLVM_LIBC_FUNCTION(long, __llvm_libc_syscall,
+                   (long number, long arg1, long arg2, long arg3, long arg4,
+                    long arg5, long arg6)) {
   long ret =
-      __llvm_libc::syscall(SYS_linkat, AT_FDCWD, path1, AT_FDCWD, path2, 0);
-#else
-#error "SYS_link or SYS_linkat not available."
-#endif
-  if (ret < 0) {
+      __llvm_libc::syscall_impl(number, arg1, arg2, arg3, arg4, arg5, arg6);
+  // Syscalls may return large positive values that overflow, but will never
+  // return values between -4096 and -1
+  if (static_cast<unsigned long>(ret) > -4096UL) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/truncate.cpp

 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 #include <unistd.h>
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, truncate, (const char *path, off_t len)) {
-  int ret = __llvm_libc::syscall(SYS_truncate, path, len);
+  int ret = __llvm_libc::syscall_impl(SYS_truncate, path, len);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/unlink.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, unlink, (const char *path)) {
 #ifdef SYS_unlink
-  long ret = __llvm_libc::syscall(SYS_unlink, path);
+  long ret = __llvm_libc::syscall_impl(SYS_unlink, path);
 #elif defined(SYS_unlinkat)
-  long ret = __llvm_libc::syscall(SYS_unlinkat, AT_FDCWD, path, 0);
+  long ret = __llvm_libc::syscall_impl(SYS_unlinkat, AT_FDCWD, path, 0);
 #else
 #error "Unlink syscalls not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/unlinkat.cpp

 #include <errno.h>
 #include <fcntl.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(int, unlinkat, (int dfd, const char *path, int flags)) {
 #ifdef SYS_unlinkat
-  long ret = __llvm_libc::syscall(SYS_unlinkat, dfd, path, flags);
+  long ret = __llvm_libc::syscall_impl(SYS_unlinkat, dfd, path, flags);
 #else
 #error "unlinkat syscall not available."
 #endif
 
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return 0;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/linux/write.cpp

 #include "src/__support/common.h"
 
 #include <errno.h>
 #include <sys/syscall.h> // For syscall numbers.
 
 namespace __llvm_libc {
 
 LLVM_LIBC_FUNCTION(ssize_t, write, (int fd, const void *buf, size_t count)) {
-  long ret = __llvm_libc::syscall(SYS_write, fd, buf, count);
+  long ret = __llvm_libc::syscall_impl(SYS_write, fd, buf, count);
   if (ret < 0) {
     errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/src/unistd/syscall.h

+//===-- Implementation header for syscall -----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_UNISTD_SYSCALL_H
+#define LLVM_LIBC_SRC_UNISTD_SYSCALL_H
+
+#include <stdarg.h>
+#include <unistd.h>
+
+namespace __llvm_libc {
+
+long __llvm_libc_syscall(long number, long arg1, long arg2, long arg3,
+                         long arg4, long arg5, long arg6);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_UNISTD_SYSCALL_H

libc/test/src/__support/OSUtil/linux/x86_64/syscall_test.cpp

 #include "utils/UnitTest/Test.h"
 
 TEST(LlvmLibcX86_64_SyscallTest, APITest) {
   // We only do a signature test here. Actual functionality tests are
   // done by the unit tests of the syscall wrappers like mmap.
 
   using __llvm_libc::cpp::function;
 
-  function<long(long)> f([](long n) { return __llvm_libc::syscall(n); });
+  function<long(long)> f([](long n) { return __llvm_libc::syscall_impl(n); });
   function<long(long, long)> f1(
-      [](long n, long a1) { return __llvm_libc::syscall(n, a1); });
-  function<long(long, long, long)> f2(
-      [](long n, long a1, long a2) { return __llvm_libc::syscall(n, a1, a2); });
+      [](long n, long a1) { return __llvm_libc::syscall_impl(n, a1); });
+  function<long(long, long, long)> f2([](long n, long a1, long a2) {
+    return __llvm_libc::syscall_impl(n, a1, a2);
+  });
   function<long(long, long, long, long)> f3(
       [](long n, long a1, long a2, long a3) {
-        return __llvm_libc::syscall(n, a1, a2, a3);
+        return __llvm_libc::syscall_impl(n, a1, a2, a3);
       });
   function<long(long, long, long, long, long)> f4(
       [](long n, long a1, long a2, long a3, long a4) {
-        return __llvm_libc::syscall(n, a1, a2, a3, a4);
+        return __llvm_libc::syscall_impl(n, a1, a2, a3, a4);
       });
   function<long(long, long, long, long, long, long)> f5(
       [](long n, long a1, long a2, long a3, long a4, long a5) {
-        return __llvm_libc::syscall(n, a1, a2, a3, a4, a5);
+        return __llvm_libc::syscall_impl(n, a1, a2, a3, a4, a5);
       });
   function<long(long, long, long, long, long, long, long)> f6(
       [](long n, long a1, long a2, long a3, long a4, long a5, long a6) {
-        return __llvm_libc::syscall(n, a1, a2, a3, a4, a5, a6);
+        return __llvm_libc::syscall_impl(n, a1, a2, a3, a4, a5, a6);
       });
 
   function<long(long, void *)> not_long_type(
-      [](long n, void *a1) { return __llvm_libc::syscall(n, a1); });
+      [](long n, void *a1) { return __llvm_libc::syscall_impl(n, a1); });
 }

libc/test/src/sched/affinity_test.cpp

 #include <errno.h>
 #include <sched.h>
 #include <sys/syscall.h>
 
 TEST(LlvmLibcSchedAffinityTest, SmokeTest) {
   cpu_set_t mask;
   errno = 0;
   using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
-  pid_t tid = __llvm_libc::syscall(SYS_gettid);
+  pid_t tid = __llvm_libc::syscall_impl(SYS_gettid);
   ASSERT_GT(tid, pid_t(0));
   // We just get and set the same mask.
   ASSERT_THAT(__llvm_libc::sched_getaffinity(tid, sizeof(cpu_set_t), &mask),
               Succeeds(0));
   ASSERT_THAT(__llvm_libc::sched_setaffinity(tid, sizeof(cpu_set_t), &mask),
               Succeeds(0));
 }
 
 TEST(LlvmLibcSchedAffinityTest, BadMask) {
   using __llvm_libc::testing::ErrnoSetterMatcher::Fails;
-  pid_t tid = __llvm_libc::syscall(SYS_gettid);
+  pid_t tid = __llvm_libc::syscall_impl(SYS_gettid);
 
   errno = 0;
   ASSERT_THAT(__llvm_libc::sched_getaffinity(tid, sizeof(cpu_set_t), nullptr),
               Fails(EFAULT));
 
   errno = 0;
   ASSERT_THAT(__llvm_libc::sched_setaffinity(tid, sizeof(cpu_set_t), nullptr),
               Fails(EFAULT));
 
   errno = 0;
 }

libc/test/src/unistd/CMakeLists.txt

add_libc_unittest(
   geteuid_test
   SUITE
     libc_unistd_unittests
   SRCS
     geteuid_test.cpp
   DEPENDS
     libc.src.unistd.geteuid
 )
+
+add_libc_unittest(
+  syscall_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    syscall_test.cpp
+  DEPENDS
+    libc.src.unistd.__llvm_libc_syscall
+    libc.include.errno
+    libc.include.unistd
+    libc.include.fcntl
+    libc.include.sys_syscall
+    libc.test.errno_setter_matcher
+)

libc/test/src/unistd/syscall_test.cpp

+//===-- Unittests for syscalls --------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/syscall.h"
+#include "test/ErrnoSetterMatcher.h"
+#include "utils/UnitTest/Test.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/syscall.h> // For syscall numbers.
+#include <unistd.h>
+
+using __llvm_libc::testing::ErrnoSetterMatcher::Succeeds;
+
+// We only do a smoke test here. Actual functionality tests are
+// done by the unit tests of the syscall wrappers like mmap.
+// The goal is to test syscalls with a wide number of args.
+
+// There is no function named "syscall" in llvm-libc, we instead use a macro to
+// set up the arguments properly. We still need to specify the namespace though
+// because the macro generates a call to the actual internal function
+// (__llvm_libc_syscall) which is inside the namespace.
+TEST(LlvmLibcSyscallTest, TrivialCall) {
+  errno = 0;
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_gettid), 0l);
+  ASSERT_EQ(errno, 0);
+}
+
+TEST(LlvmLibcSyscallTest, SymlinkCreateDestroy) {
+  constexpr const char LINK_VAL[] = "syscall_readlink_test_value";
+  constexpr const char LINK[] = "testdata/syscall_readlink.test.link";
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_symlink, LINK_VAL, LINK), 0l);
+  ASSERT_EQ(errno, 0);
+
+  char buf[sizeof(LINK_VAL)];
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_readlink, LINK, buf, sizeof(buf)), 0l);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_unlink, LINK), 0l);
+  ASSERT_EQ(errno, 0);
+}
+
+TEST(LlvmLibcSyscallTest, FileReadWrite) {
+  constexpr const char HELLO[] = "hello";
+  constexpr int HELLO_SIZE = sizeof(HELLO);
+
+  constexpr const char *TEST_FILE = "testdata/syscall_pread_pwrite.test";
+
+  int fd =
+      __llvm_libc::syscall(SYS_open, TEST_FILE, O_WRONLY | O_CREAT, S_IRWXU);
+  ASSERT_GT(fd, 0);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_pwrite64, fd, HELLO, HELLO_SIZE, 0), 0l);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_fsync, fd), 0l);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_close, fd), 0l);
+  ASSERT_EQ(errno, 0);
+}
+
+TEST(LlvmLibcSyscallTest, FileLinkCreateDestroy) {
+  constexpr const char *TEST_DIR = "testdata";
+  constexpr const char *TEST_FILE = "syscall_linkat.test";
+  constexpr const char *TEST_FILE_PATH = "testdata/syscall_linkat.test";
+  constexpr const char *TEST_FILE_LINK = "syscall_linkat.test.link";
+  constexpr const char *TEST_FILE_LINK_PATH =
+      "testdata/syscall_linkat.test.link";
+
+  // The test strategy is as follows:
+  //   1. Create a normal file
+  //   2. Create a link to that file.
+  //   3. Open the link to check that the link was created.
+  //   4. Cleanup the file and its link.
+
+  int write_fd = __llvm_libc::syscall(SYS_open, TEST_FILE_PATH,
+                                      O_WRONLY | O_CREAT, S_IRWXU);
+  ASSERT_GT(write_fd, 0);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_close, write_fd), 0l);
+  ASSERT_EQ(errno, 0);
+
+  int dir_fd = __llvm_libc::syscall(SYS_open, TEST_DIR, O_DIRECTORY, 0);
+  ASSERT_GT(dir_fd, 0);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_linkat, dir_fd, TEST_FILE, dir_fd,
+                                 TEST_FILE_LINK, 0),
+            0l);
+  ASSERT_EQ(errno, 0);
+
+  int link_fd = __llvm_libc::syscall(SYS_open, TEST_FILE_LINK_PATH, O_PATH, 0);
+  ASSERT_GT(link_fd, 0);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_unlink, TEST_FILE_PATH), 0l);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_unlink, TEST_FILE_LINK_PATH), 0l);
+  ASSERT_EQ(errno, 0);
+
+  ASSERT_GE(__llvm_libc::syscall(SYS_close, dir_fd), 0l);
+  ASSERT_EQ(errno, 0);
+}