linux-kernel - [PATCH 05/17] Use C version for SYSCALL

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Date:   Thu, 21 Mar 2019 14:59:57 -0700
From:   Andi Kleen <andi@...stfloor.org>
To:     x86@...nel.org
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 05/17] Use C version for SYSCALL_ALIAS

From: Andi Kleen <ak@...ux.intel.com>

LTO doesn't like the assembler aliasing used for SYSCALL_ALIAS.
Replace it with C aliasing. Also mark the only users visible.

This gives cleaner and nicer code, so is useful even without
LTO.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/include/asm/syscall_wrapper.h | 1 +
 include/linux/linkage.h                | 6 ++----
 kernel/time/posix-stubs.c              | 2 +-
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/syscall_wrapper.h b/arch/x86/include/asm/syscall_wrapper.h
index e046a405743d..6f7a73da8437 100644
--- a/arch/x86/include/asm/syscall_wrapper.h
+++ b/arch/x86/include/asm/syscall_wrapper.h
@@ -52,6 +52,7 @@
 	SYSCALL_METADATA(_##sname, 0);				\
 	asmlinkage long __x64_sys_##sname(void);		\
 	ALLOW_ERROR_INJECTION(__x64_sys_##sname, ERRNO);	\
+	asmlinkage long __ia32_sys_##sname(void);		\
 	SYSCALL_ALIAS(__ia32_sys_##sname, __x64_sys_##sname);	\
 	asmlinkage long __x64_sys_##sname(void)
 
diff --git a/include/linux/linkage.h b/include/linux/linkage.h
index 7e020782ade2..5fc9ecd55bda 100644
--- a/include/linux/linkage.h
+++ b/include/linux/linkage.h
@@ -30,10 +30,8 @@
 #endif
 
 #ifndef SYSCALL_ALIAS
-#define SYSCALL_ALIAS(alias, name) asm(			\
-	".globl " __stringify(alias) "\n\t"		\
-	".set   " __stringify(alias) ","		\
-		  __stringify(name))
+#define SYSCALL_ALIAS(a, name) \
+	__visible typeof(a) a __attribute__((alias(__stringify(name))))
 #endif
 
 #define __page_aligned_data	__section(.data..page_aligned) __aligned(PAGE_SIZE)
diff --git a/kernel/time/posix-stubs.c b/kernel/time/posix-stubs.c
index 67df65f887ac..4777892bee82 100644
--- a/kernel/time/posix-stubs.c
+++ b/kernel/time/posix-stubs.c
@@ -21,7 +21,7 @@
 #include <asm/syscall_wrapper.h>
 #endif
 
-asmlinkage long sys_ni_posix_timers(void)
+__visible asmlinkage long sys_ni_posix_timers(void)
 {
 	pr_err_once("process %d (%s) attempted a POSIX timer syscall "
 		    "while CONFIG_POSIX_TIMERS is not set\n",
-- 
2.20.1