[libc] Add linux aarch64 syscall implementation.

[sivachandra]

Summary

Add mmap and munmap to the linux aarch64 entrypoint list as the first
user of these syscalls.

[abrachet]

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

16

I think register is (or soon to be) deprecated and reserved, and my understanding is that most compilers completely ignore it anyway. Should it be omitted here?

[sivachandra]

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

16

Oh, I didn't know that. But, when I try, I get warnings like this:

warning: ignored asm label 'r10' on automatic variable
  long r10 __asm__("r10") = 123;

The allocation is not in the register and the syscalls end up with wrong number of args.

[michaelrj]

LGTM

libc/config/linux/aarch64/entrypoints.txt

set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl
     libc.src.math.trunc
     libc.src.math.truncf
     libc.src.math.truncl
 )
 
+if(LLVM_LIBC_FULL_BUILD)
+  list(APPEND TARGET_LIBC_ENTRYPOINTS
+    # sys/mman.h entrypoints
+    libc.src.sys.mman.mmap
+    libc.src.sys.mman.munmap
+  )
+endif()
+
 set(TARGET_LLVMLIBC_ENTRYPOINTS
   ${TARGET_LIBC_ENTRYPOINTS}
   ${TARGET_LIBM_ENTRYPOINTS}
 )

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

+add_subdirectory(aarch64)
 add_subdirectory(x86_64)
 
 add_header_library(
   linux_util
   HDRS
     io.h
     quick_exit.h
     syscall.h
   DEPENDS
+    .aarch64.linux_aarch64_util
     .x86_64.linux_x86_64_util
     libc.src.__support.common
 )

libc/src/__support/OSUtil/linux/aarch64/CMakeLists.txt

+add_header_library(
+  linux_aarch64_util
+  HDRS
+    syscall.h
+  DEPENDS
+    libc.src.__support.common
+)

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

+//===--------- inline implementation of aarch64 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_AARCH64_SYSCALL_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_AARCH64_SYSCALL_H
+
+#include "src/__support/common.h"
+
+#define REGISTER_DECL_0                                                        \
+  register long x8 __asm__("x8") = number;                                     \
+  register long x0 __asm__("x0");
+#define REGISTER_DECL_1                                                        \
+  register long x8 __asm__("x8") = number;                                     \
+  register long x0 __asm__("x0") = arg1;
+#define REGISTER_DECL_2 REGISTER_DECL_1 register long x1 __asm__("x1") = arg2;
+#define REGISTER_DECL_3                                                        \
+  REGISTER_DECL_2                                                              \
+  register long x2 __asm__("x2") = arg3;
+#define REGISTER_DECL_4                                                        \
+  REGISTER_DECL_3                                                              \
+  register long x3 __asm__("x3") = arg4;
+#define REGISTER_DECL_5                                                        \
+  REGISTER_DECL_4                                                              \
+  register long x4 __asm__("x4") = arg5;
+#define REGISTER_DECL_6                                                        \
+  REGISTER_DECL_5                                                              \
+  register long x5 __asm__("x5") = arg6;
+
+#define REGISTER_CONSTRAINT_0 "r"(x8)
+#define REGISTER_CONSTRAINT_1 REGISTER_CONSTRAINT_0, "r"(x0)
+#define REGISTER_CONSTRAINT_2 REGISTER_CONSTRAINT_1, "r"(x1)
+#define REGISTER_CONSTRAINT_3 REGISTER_CONSTRAINT_2, "r"(x2)
+#define REGISTER_CONSTRAINT_4 REGISTER_CONSTRAINT_3, "r"(x3)
+#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) {
+  REGISTER_DECL_0;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_0);
+  return x0;
+}
+
+__attribute__((always_inline)) inline long syscall(long number, long arg1) {
+  REGISTER_DECL_1;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_1);
+  return x0;
+}
+
+__attribute__((always_inline)) inline long syscall(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,
+                                                   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) {
+  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) {
+  REGISTER_DECL_5;
+  SYSCALL_INSTR(REGISTER_CONSTRAINT_5);
+  return x0;
+}
+
+__attribute__((always_inline)) inline long syscall(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
+#undef REGISTER_DECL_1
+#undef REGISTER_DECL_2
+#undef REGISTER_DECL_3
+#undef REGISTER_DECL_4
+#undef REGISTER_DECL_5
+#undef REGISTER_DECL_6
+
+#undef REGISTER_CONSTRAINT_0
+#undef REGISTER_CONSTRAINT_1
+#undef REGISTER_CONSTRAINT_2
+#undef REGISTER_CONSTRAINT_3
+#undef REGISTER_CONSTRAINT_4
+#undef REGISTER_CONSTRAINT_5
+#undef REGISTER_CONSTRAINT_6
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_AARCH64_SYSCALL_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"
+#elif defined(LLVM_LIBC_ARCH_AARCH64)
+#include "aarch64/syscall.h"
 #endif
 
+namespace __llvm_libc {
+
+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...);
+}
+
+} // namespace __llvm_libc
+
 #endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_LINUX_SYSCALL_H

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

__attribute__((always_inline)) inline long syscall(long __number, long __arg1,
   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;
 }
 
-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