[libc-commits] [libc] [libc] Force to inline syscall_impl on x86_64 (PR #178153)

[Jakob Koschel via libc-commits]

https://github.com/jakos-sec updated https://github.com/llvm/llvm-project/pull/178153

>From 9a31abfb5bf7b79fa8cdc674c9e7015c52ad54ab Mon Sep 17 00:00:00 2001
From: Jakob Koschel <jakobkoschel at google.com>
Date: Tue, 27 Jan 2026 10:22:50 +0000
Subject: [PATCH] Force to inline syscall_impl on x86_64

With currently only LIBC_INLINE, we just hint the compiler to inline
the function which however in practice is not always the case.

This is in preparation for adding SHSTK support which requires
the system call enabling it to be inlined into do_start().
---
 .../__support/OSUtil/linux/x86_64/syscall.h   | 29 +++++++++++--------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/libc/src/__support/OSUtil/linux/x86_64/syscall.h b/libc/src/__support/OSUtil/linux/x86_64/syscall.h
index ebd77980af6a4..f069d46185d0f 100644
--- a/libc/src/__support/OSUtil/linux/x86_64/syscall.h
+++ b/libc/src/__support/OSUtil/linux/x86_64/syscall.h
@@ -16,7 +16,7 @@
 
 namespace LIBC_NAMESPACE_DECL {
 
-LIBC_INLINE long syscall_impl(long __number) {
+[[gnu::always_inline]] LIBC_INLINE long syscall_impl(long __number) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
@@ -25,7 +25,8 @@ LIBC_INLINE long syscall_impl(long __number) {
   return retcode;
 }
 
-LIBC_INLINE long syscall_impl(long __number, long __arg1) {
+[[gnu::always_inline]] LIBC_INLINE long syscall_impl(long __number,
+                                                     long __arg1) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
@@ -34,7 +35,8 @@ LIBC_INLINE long syscall_impl(long __number, long __arg1) {
   return retcode;
 }
 
-LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2) {
+[[gnu::always_inline]] LIBC_INLINE long syscall_impl(long __number, long __arg1,
+                                                     long __arg2) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
@@ -43,8 +45,8 @@ LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2) {
   return retcode;
 }
 
-LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2,
-                              long __arg3) {
+[[gnu::always_inline]] LIBC_INLINE long syscall_impl(long __number, long __arg1,
+                                                     long __arg2, long __arg3) {
   long retcode;
   LIBC_INLINE_ASM("syscall"
                   : "=a"(retcode)
@@ -53,8 +55,9 @@ LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2,
   return retcode;
 }
 
-LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2,
-                              long __arg3, long __arg4) {
+[[gnu::always_inline]] LIBC_INLINE long syscall_impl(long __number, long __arg1,
+                                                     long __arg2, long __arg3,
+                                                     long __arg4) {
   long retcode;
   register long r10 __asm__("r10") = __arg4;
   LIBC_INLINE_ASM("syscall"
@@ -65,8 +68,9 @@ LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2,
   return retcode;
 }
 
-LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2,
-                              long __arg3, long __arg4, long __arg5) {
+[[gnu::always_inline]] LIBC_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;
@@ -78,9 +82,10 @@ LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2,
   return retcode;
 }
 
-LIBC_INLINE long syscall_impl(long __number, long __arg1, long __arg2,
-                              long __arg3, long __arg4, long __arg5,
-                              long __arg6) {
+[[gnu::always_inline]] LIBC_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;