[libc] Move the x86_64 syscall functions to OSUtil.

libc/config/linux/CMakeLists.txt

-add_gen_header(
-  linux_syscall_h
-  DEF_FILE syscall.h.def
-  GEN_HDR syscall.h
-  PARAMS
-    inline_syscalls=${LIBC_TARGET_ARCHITECTURE}/syscall.h.inc
-  DATA_FILES
-    ${LIBC_TARGET_ARCHITECTURE}/syscall.h.inc
-  DEPENDS
-    libc.src.__support.common
-)
-
 add_header(
   app_h
   HDR
     app.h
 )

libc/loader/linux/x86_64/CMakeLists.txt

 add_loader_object(
   crt1
   SRC
     start.cpp
   DEPENDS
-    libc.config.linux.linux_syscall_h
     libc.config.linux.app_h
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
     libc.src.string.memcpy
     libc.src.sys.mman.mmap
   COMPILE_OPTIONS
     -fno-omit-frame-pointer
     -ffreestanding # To avoid compiler warnings about calling the main function.
 )

libc/loader/linux/x86_64/start.cpp

 //===-- Implementation of crt for x86_64 ----------------------------------===//
 //
 // 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 "config/linux/app.h"
-#include "config/linux/syscall.h"
 #include "include/sys/mman.h"
 #include "include/sys/syscall.h"
+#include "src/__support/OSUtil/syscall.h"
 #include "src/string/memcpy.h"
 #include "src/sys/mman/mmap.h"
 
 #include <asm/prctl.h>
 #include <linux/auxvec.h>
 #include <linux/elf.h>
 #include <stdint.h>
 

libc/src/__support/OSUtil/CMakeLists.txt

 add_subdirectory(linux)
 
 add_header_library(
   osutil
   HDRS
     io.h
     quick_exit.h
+    syscall.h
   DEPENDS
     libc.src.__support.OSUtil.linux.linux_util
 )

libc/src/__support/OSUtil/linux/CMakeLists.txt

+add_subdirectory(x86_64)
+
 add_header_library(
   linux_util
   HDRS
     io.h
     quick_exit.h
+    syscall.h
   DEPENDS
-    libc.config.linux.linux_syscall_h
-    libc.include.sys_syscall
-    libc.src.string.string_utils
+    .x86_64.linux_x86_64_util
+    libc.src.__support.common
 )

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

 //===-------------- Linux implementation of IO utils ------------*- 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_SUPPORT_OSUTIL_LINUX_IO_H
 #define LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_IO_H
 
-#include "config/linux/syscall.h" // For internal syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
+#include "include/sys/syscall.h" // For syscall numbers.
 #include "src/string/string_utils.h"
+#include "syscall.h" // For internal syscall function.
 
 namespace __llvm_libc {
 
 static inline void write_to_stderr(const char *msg) {
   __llvm_libc::syscall(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

 //===---------- Linux implementation of a quick exit function ---*- 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_SUPPORT_OSUTIL_LINUX_QUICK_EXIT_H
 #define LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_QUICK_EXIT_H
 
-#include "config/linux/syscall.h" // For internal syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
+#include "include/sys/syscall.h" // For syscall numbers.
+#include "syscall.h"             // For internal syscall function.
 
 namespace __llvm_libc {
 
 static inline void quick_exit(int status) {
   for (;;) {
     __llvm_libc::syscall(SYS_exit_group, status);
     __llvm_libc::syscall(SYS_exit, status);
   }
 }
 
 } // namespace __llvm_libc
 
 #endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_QUICK_EXIT_H

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

+//===----------------------- Linux syscalls ---------------------*- 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_SUPPORT_OSUTIL_LINUX_SYSCALL_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_SYSCALL_H
+
+#include "src/__support/architectures.h"
+
+#ifdef LLVM_LIBC_ARCH_X86_64
+#include "x86_64/syscall.h"
+#endif
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_SYSCALL_H

libc/src/__support/OSUtil/linux/x86_64/CMakeLists.txt

+add_header_library(
+  linux_x86_64_util
+  HDRS
+    syscall.h
+  DEPENDS
+    libc.src.__support.common
+)

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

-//===------------ inline implementation of x86_64 syscalls ----------------===//
+//===---------- inline implementation of x86_64 syscalls ----------* 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
 //
 //===----------------------------------------------------------------------===//
 
-%%begin()
+#ifndef LLVM_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) {

 }
 
 template <typename... Ts>
 __attribute__((always_inline)) inline long syscall(long __number, Ts... ts) {
   static_assert(sizeof...(Ts) <= 6, "Too many arguments for syscall");
   return syscall(__number, (long)ts...);
 }
 
-
 #undef SYSCALL_CLOBBER_LIST
 
 } // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_X86_64_SYSCALL_H

libc/src/__support/OSUtil/syscall.h

 //===--------------- Internal syscall declarations --------------*- 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_CONFIG_LINUX_SYSCALL_H
-#define LLVM_LIBC_CONFIG_LINUX_SYSCALL_H
+#ifndef LLVM_LIBC_SRC_SUPPORT_OSUTIL_SYSCALL_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_SYSCALL_H
 
-%%include_file(${inline_syscalls})
+#ifdef __unix__
+#include "linux/syscall.h"
+#endif
 
-#endif // LLVM_LIBC_CONFIG_LINUX_SYSCALL_H
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_SYSCALL_H

libc/src/assert/CMakeLists.txt

 add_entrypoint_object(
   __assert_fail
   SRCS
     __assert_fail.cpp
   HDRS
     __assert_fail.h
     assert.h
   DEPENDS
     # These two dependencies are temporary and should be replaced by fprintf
     # later.
-    libc.config.linux.linux_syscall_h
+    libc.src.__support.OSUtil.osutil
     libc.include.sys_syscall
     libc.src.stdlib.abort
 )

libc/src/assert/__assert_fail.cpp

 //===-- Implementation of __assert_fail -----------------------------------===//
 //
 // 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/assert/__assert_fail.h"
 #include "src/stdlib/abort.h"
 
 // These includes are temporary.
-#include "config/linux/syscall.h" // For internal syscall function.
 #include "include/sys/syscall.h"  // For syscall numbers.
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 
 namespace __llvm_libc {
 
 // This is just a temporary solution to make assert available to internal
 // llvm libc code. In the future writeToStderr will not exist and __assert_fail
 // will call fprintf(stderr, ...).
 static void write_to_stderr(const char *s) {
   size_t length = 0;

libc/src/signal/linux/CMakeLists.txt

 
 add_entrypoint_object(
   raise
   SRCS
     raise.cpp
   HDRS
     signal.h
     ../raise.h
   DEPENDS
-    libc.config.linux.linux_syscall_h
     libc.include.signal
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
 )
 
 add_object_library(
   __restore
   SRCS
     __restore.cpp
   COMPILE_OPTIONS
     -fomit-frame-pointer
     -O3
     -Wframe-larger-than=0
     -Werror
     -Wno-attributes
     # asan creates asan.module_ctor which uses stack space, causing warnings.
     -fno-sanitize=address
   DEPENDS
-    libc.config.linux.linux_syscall_h
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
 )
 
 add_entrypoint_object(
   sigaction
   SRCS
     sigaction.cpp
   HDRS
     signal.h
     ../sigaction.h
   DEPENDS
     .__restore
-    libc.config.linux.linux_syscall_h
     libc.include.signal
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
     libc.src.errno.__errno_location
 )
 
 add_entrypoint_object(
   sigprocmask
   SRCS
     sigprocmask.cpp
   HDRS
     signal.h
     ../sigprocmask.h
   DEPENDS
-    libc.config.linux.linux_syscall_h
     libc.include.signal
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
     libc.src.errno.__errno_location
 )
 
 add_entrypoint_object(
   sigemptyset
   SRCS
     sigemptyset.cpp
   HDRS

libc/src/signal/linux/__restore.cpp

 //===-- Linux implementation of __restore_rt ------------------------------===//
 //
 // 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
 //
 //===----------------------------------------------------------------------===//
 
 // This file is implemented separately from sigaction.cpp so that we can
 // strongly control the options this file is compiled with. __restore_rt cannot
 // make any stack allocations so we must ensure this.
 
-#include "config/linux/syscall.h"
 #include "include/sys/syscall.h"
+#include "src/__support/OSUtil/syscall.h"
 
 namespace __llvm_libc {
 
 extern "C" void __restore_rt()
     __attribute__((no_sanitize("thread", "memory", "undefined", "fuzzer"),
                    hidden));
 
 extern "C" void __restore_rt() { __llvm_libc::syscall(SYS_rt_sigreturn); }
 
 } // namespace __llvm_libc

libc/src/signal/linux/signal.h

 //===-- Internal header for Linux signals -----------------------*- 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_SIGNAL_LINUX_SIGNAL_H
 #define LLVM_LIBC_SRC_SIGNAL_LINUX_SIGNAL_H
 
-#include "config/linux/syscall.h" // For internal syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 
 #include "include/signal.h"
 
 static_assert(sizeof(sigset_t) * 8 >= NSIG, "sigset_t cannot hold all signals");
 
 namespace __llvm_libc {
 
 // Using this internally defined type will make it easier in the future to port

libc/src/stdlib/linux/CMakeLists.txt

 add_entrypoint_object(
   _Exit
   SRCS
     _Exit.cpp
   HDRS
     ../_Exit.h
   DEPENDS
     libc.include.sys_syscall
-    libc.config.linux.linux_syscall_h
     libc.include.stdlib
+    libc.src.__support.OSUtil.osutil
 )

libc/src/stdlib/linux/_Exit.cpp

 //===------------------- Linux Implementation of _Exit --------------------===//
 //
 // 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 "config/linux/syscall.h" // For internal syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #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);
   }
 }
 
 } // namespace __llvm_libc

libc/src/sys/mman/linux/CMakeLists.txt

 add_entrypoint_object(
   mmap
   SRCS
     mmap.cpp
   HDRS
     ../mmap.h
   DEPENDS
-    libc.config.linux.linux_syscall_h
     libc.include.sys_mman
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
     libc.src.errno.__errno_location
 )
 
 add_entrypoint_object(
   munmap
   SRCS
     munmap.cpp
   HDRS
     ../munmap.h
   DEPENDS
-    libc.config.linux.linux_syscall_h
     libc.include.sys_mman
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
     libc.src.errno.__errno_location
 )

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

 //===---------- Linux implementation of the POSIX mmap function -----------===//
 //
 // 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/sys/mman/mmap.h"
 
-#include "config/linux/syscall.h" // For internal syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 #include "src/errno/llvmlibc_errno.h"
 
 #include <linux/param.h> // For EXEC_PAGESIZE.
 
 namespace __llvm_libc {
 
 // This function is currently linux only. It has to be refactored suitably if

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

 //===---------- Linux implementation of the POSIX munmap function ---------===//
 //
 // 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/sys/mman/munmap.h"
 
-#include "config/linux/syscall.h" // For internal syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 #include "src/errno/llvmlibc_errno.h"
 
 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)) {

libc/src/threads/linux/CMakeLists.txt

 add_entrypoint_object(
   call_once
   SRCS
     call_once.cpp
   HDRS
     ../call_once.h
   DEPENDS
     .threads_utils
-    libc.config.linux.linux_syscall_h
     libc.include.sys_syscall
     libc.include.threads
+    libc.src.__support.OSUtil.osutil
 )
 
 add_header_library(
   threads_utils
   HDRS
     CndVar.h
     Futex.h
     Mutex.h
     Thread.h
   DEPENDS
     .thread_start_args_h
-    libc.config.linux.linux_syscall_h
     libc.include.sys_syscall
     libc.include.threads
+    libc.src.__support.OSUtil.osutil
 )
 
 add_entrypoint_object(
   thrd_create
   SRCS
     thrd_create.cpp
   HDRS
     ../thrd_create.h
   DEPENDS
     .threads_utils
-    libc.config.linux.linux_syscall_h
     libc.include.errno
     libc.include.sys_syscall
     libc.include.threads
     libc.src.__support.common
+    libc.src.__support.OSUtil.osutil
     libc.src.errno.__errno_location
     libc.src.sys.mman.mmap
   COMPILE_OPTIONS
     -O3
     -fno-omit-frame-pointer # This allows us to sniff out the thread args from
                             # the new thread's stack reliably.
 )
 
 add_entrypoint_object(
   thrd_join
   SRCS
     thrd_join.cpp
   HDRS
     ../thrd_join.h
   DEPENDS
     .threads_utils
-    libc.config.linux.linux_syscall_h
     libc.include.sys_syscall
     libc.include.threads
-    libc.src.sys.mman.munmap
     libc.src.__support.common
+    libc.src.__support.OSUtil.osutil
+    libc.src.sys.mman.munmap
 )
 
 add_entrypoint_object(
   mtx_init
   SRCS
     mtx_init.cpp
   HDRS
     ../mtx_init.h

libc/src/threads/linux/CndVar.h

 //===-- Utility condition variable class ------------------------*- 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_THREADS_LINUX_CNDVAR_H
 #define LLVM_LIBC_SRC_THREADS_LINUX_CNDVAR_H
 
 #include "Futex.h"
 #include "Mutex.h"
 
-#include "config/linux/syscall.h" // For syscall functions.
-#include "include/sys/syscall.h"  // For syscall numbers.
-#include "include/threads.h"      // For values like thrd_success etc.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "include/threads.h"              // For values like thrd_success etc.
+#include "src/__support/OSUtil/syscall.h" // For syscall functions.
 
 #include <linux/futex.h> // For futex operations.
 #include <stdatomic.h>   // For atomic operations
 
 namespace __llvm_libc {
 
 struct CndVar {
   enum CndWaiterStatus : uint32_t {

libc/src/threads/linux/Mutex.h

 //===-- Utility mutex classes -----------------------------------*- 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_THREADS_LINUX_MUTEX_H
 #define LLVM_LIBC_SRC_THREADS_LINUX_MUTEX_H
 
 #include "Futex.h"
 
-#include "config/linux/syscall.h" // For syscall functions.
-#include "include/sys/syscall.h"  // For syscall numbers.
-#include "include/threads.h"      // For values like thrd_success etc.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "include/threads.h"              // For values like thrd_success etc.
+#include "src/__support/OSUtil/syscall.h" // For syscall functions.
 
 #include <linux/futex.h> // For futex operations.
 #include <stdatomic.h>
 #include <stdint.h>
 
 namespace __llvm_libc {
 
 struct Mutex {

libc/src/threads/linux/call_once.cpp

 //===-- Linux implementation of the call_once function --------------------===//
 //
 // 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/threads/call_once.h"
-#include "config/linux/syscall.h" // For syscall functions.
-#include "include/sys/syscall.h"  // For syscall numbers.
-#include "include/threads.h"      // For call_once related type definition.
+#include "include/sys/syscall.h" // For syscall numbers.
+#include "include/threads.h"     // For call_once related type definition.
+#include "src/__support/OSUtil/syscall.h" // For syscall functions.
 #include "src/__support/common.h"
 #include "src/threads/linux/Futex.h"
 
 #include <limits.h>
 #include <linux/futex.h>
 #include <stdatomic.h>
 
 namespace __llvm_libc {

libc/src/threads/linux/thrd_create.cpp

 //===-- Linux implementation of the thrd_create function ------------------===//
 //
 // 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/threads/thrd_create.h"
-#include "config/linux/syscall.h" // For syscall function.
-#include "include/errno.h"        // For E* error values.
-#include "include/sys/mman.h"     // For PROT_* and MAP_* definitions.
-#include "include/sys/syscall.h"  // For syscall numbers.
-#include "include/threads.h"      // For thrd_* type definitions.
+#include "include/errno.h"                // For E* error values.
+#include "include/sys/mman.h"             // For PROT_* and MAP_* definitions.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "include/threads.h"              // For thrd_* type definitions.
+#include "src/__support/OSUtil/syscall.h" // For syscall function.
 #include "src/__support/common.h"
 #include "src/errno/llvmlibc_errno.h"
 #include "src/sys/mman/mmap.h"
 #include "src/sys/mman/munmap.h"
 #include "src/threads/linux/Futex.h"
 #include "src/threads/linux/Thread.h"
 
 #include <linux/sched.h> // For CLONE_* flags.

libc/src/threads/linux/thrd_join.cpp

 //===-- Linux implementation of the thrd_join function --------------------===//
 //
 // 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/threads/thrd_join.h"
-#include "config/linux/syscall.h" // For syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
-#include "include/threads.h"      // For thrd_* type definitions.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "include/threads.h"              // For thrd_* type definitions.
+#include "src/__support/OSUtil/syscall.h" // For syscall function.
 #include "src/__support/common.h"
 #include "src/sys/mman/munmap.h"
 #include "src/threads/linux/Futex.h"
 #include "src/threads/linux/Thread.h"
 
 #include <linux/futex.h> // For futex operations.
 #include <stdatomic.h>   // For atomic_load.
 

libc/src/unistd/linux/CMakeLists.txt

 add_entrypoint_object(
   write
   SRCS
     write.cpp
   HDRS
     ../write.h
   DEPENDS
     libc.include.unistd
-    libc.config.linux.linux_syscall_h
     libc.include.sys_syscall
+    libc.src.__support.OSUtil.osutil
     libc.src.errno.__errno_location
 )

libc/src/unistd/linux/write.cpp

 //===-- Linux implementation of write -------------------------------------===//
 //
 // 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/write.h"
 
-#include "config/linux/syscall.h" // For internal syscall function.
-#include "include/sys/syscall.h"  // For syscall numbers.
+#include "include/sys/syscall.h"          // For syscall numbers.
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
 #include "src/__support/common.h"
 #include "src/errno/llvmlibc_errno.h"
 
 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);
   if (ret < 0) {
     llvmlibc_errno = -ret;
     return -1;
   }
   return ret;
 }
 
 } // namespace __llvm_libc

libc/test/CMakeLists.txt

 
 add_subdirectory(src)
 add_subdirectory(utils)
 
 if(NOT LLVM_LIBC_FULL_BUILD)
   return()
 endif()
 
-add_subdirectory(config)
 add_subdirectory(integration)
 add_subdirectory(loader)

libc/test/config/CMakeLists.txt

-add_subdirectory(${LIBC_TARGET_OS})

libc/test/config/linux/CMakeLists.txt

-add_libc_testsuite(libc_linux_tests)
-
-if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/${LIBC_TARGET_ARCHITECTURE})
-  add_subdirectory(${LIBC_TARGET_ARCHITECTURE})
-endif()

libc/test/config/linux/x86_64/CMakeLists.txt

-add_libc_unittest(
-  libc_linux_x86_64_syscall_unittest
-  SUITE libc_linux_tests
-  SRCS syscall_test.cpp
-  DEPENDS
-   libc.config.linux.linux_syscall_h
-)

libc/test/src/__support/CMakeLists.txt

 set(float_test_file ${CMAKE_CURRENT_SOURCE_DIR}/str_to_float_comparison_data.txt)
 
 add_custom_command(TARGET libc_str_to_float_comparison_test
                    POST_BUILD
                    COMMAND $<TARGET_FILE:libc_str_to_float_comparison_test> ${float_test_file}
                    DEPENDS ${float_test_file}
                    COMMENT "Test the strtof and strtod implementations against precomputed results." 
                    VERBATIM)
+
+add_subdirectory(OSUtil)

libc/test/src/__support/OSUtil/CMakeLists.txt

+add_libc_testsuite(libc_osutil_tests)
+
+add_subdirectory(linux)

libc/test/src/__support/OSUtil/linux/CMakeLists.txt

+add_subdirectory(x86_64)

libc/test/src/__support/OSUtil/linux/x86_64/CMakeLists.txt

+add_libc_unittest(
+  syscall_unittest
+  SUITE libc_osutil_tests
+  SRCS syscall_test.cpp
+  DEPENDS
+   libc.src.__support.OSUtil.osutil
+)

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

 //===-- Unittests for x86_64 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 "config/linux/syscall.h"
-#include "utils/UnitTest/Test.h"
-
 #include "src/__support/CPP/Functional.h"
+#include "src/__support/OSUtil/syscall.h"
+#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); });