Use gcc alias instead of assembler aliases for syscalls

PATCH In review Andi Kleen 4 participants 6 messages Aug 5, 2013 – Aug 8, 2013 ABI/API

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Andi Kleen

author

2013-08-05 22:09 UTC #0 lore raw

PATCH 1/1 Use gcc alias instead of assembler aliases for syscalls

From: Andi Kleen <[email protected]>

Use standard gcc __attribute__((alias(foo))) to define the syscall aliases instead of custom assembler macros.

This is far cleaner, and also fixes my LTO kernel build.

Signed-off-by Andi Kleen <[email protected]>

---
 include/linux/compat.h   | 4 ++--
 include/linux/syscalls.h | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

include/linux/compat.h +2 -2

index 7f0c1dd..18e4b75 100644
@@ -41,13 +41,13 @@
 	COMPAT_SYSCALL_DEFINEx(6, _##name, __VA_ARGS__)
 
 #define COMPAT_SYSCALL_DEFINEx(x, name, ...)				\
-	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
+	asmlinkage long compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))\
+		__attribute__((alias(__stringify(compat_SyS##name))));  \
 	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));\
 	asmlinkage long compat_SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))\
 	{								\
 		return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
 	}								\
-	SYSCALL_ALIAS(compat_sys##name, compat_SyS##name);		\
 	static inline long C_SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
 #ifndef compat_user_stack_pointer

include/linux/syscalls.h +2 -2

index 4147d70..87039ad 100644
@@ -184,7 +184,8 @@ extern struct trace_event_functions exit_syscall_print_funcs;
 
 #define __PROTECT(...) asmlinkage_protect(__VA_ARGS__)
 #define __SYSCALL_DEFINEx(x, name, ...)					\
-	asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	asmlinkage long sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))	\
+		__attribute__((alias(__stringify(SyS##name))));		\
 	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
 	asmlinkage long SyS##name(__MAP(x,__SC_LONG,__VA_ARGS__))	\
 	{								\

@@ -193,7 +194,6 @@ extern struct trace_event_functions exit_syscall_print_funcs;
 		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));	\
 		return ret;						\
 	}								\
-	SYSCALL_ALIAS(sys##name, SyS##name);				\
 	static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))
 
 asmlinkage long sys_time(time_t __user *tloc);

Signature · 1 line

1.8.3.1

Andrew Morton

2013-08-06 06:01 UTC #1 lore raw

Quoted 6 lines · On Mon, 5 Aug 2013 15:09:35 -0700 Andi Kleen <[email protected]> wrote:

From: Andi Kleen <[email protected]>
Use standard gcc __attribute__((alias(foo))) to define the syscall aliases instead of custom assembler macros.
This is far cleaner, and also fixes my LTO kernel build.

I wonder what gcc version this was added in. Seems fairly longstanding.

include/linux/compat.h line 50

Quoted 4 lines

include/linux/compat.h +0 -1

 	{								\
 		return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
 	}								\
-	SYSCALL_ALIAS(compat_sys##name, compat_SyS##name);		\

I think we can remove the SYSCALL_ALIAS definitions?

Andi Kleen

author

2013-08-06 06:42 UTC #2 lore raw

Quoted 10 lines · Andrew Morton

Quoted 6 lines · On Mon, 5 Aug 2013 15:09:35 -0700 Andi Kleen <[email protected]> wrote:
From: Andi Kleen <[email protected]>
Use standard gcc __attribute__((alias(foo))) to define the syscall aliases instead of custom assembler macros.
This is far cleaner, and also fixes my LTO kernel build.
I wonder what gcc version this was added in. Seems fairly longstanding.

Seems to be already in 2.95, so every kernel compiler

http://gcc.gnu.org/onlinedocs/gcc-2.95.3/gcc_4.html#SEC90

Quoted 7 lines

include/linux/compat.h line 50
Quoted 5 lines
include/linux/compat.h +0 -1
 	{								\
 		return C_SYSC##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
 	}								\
-	SYSCALL_ALIAS(compat_sys##name, compat_SyS##name);		\
I think we can remove the SYSCALL_ALIAS definitions?

Yes will send a followon patch.

-Andi

Signature · 1 line

[email protected] -- Speaking for myself only.

Al Viro

2013-08-06 07:40 UTC #3 lore raw

Quoted 5 lines · Andi Kleen

Quoted 4 lines · Andrew Morton
Quoted 2 lines · On Mon, 5 Aug 2013 15:09:35 -0700 Andi Kleen <[email protected]> wrote:
From: Andi Kleen <[email protected]>

Quoted 8 lines

Quoted 6 lines
Quoted 4 lines
Use standard gcc __attribute__((alias(foo))) to define the syscall aliases instead of custom assembler macros.
This is far cleaner, and also fixes my LTO kernel build.
I wonder what gcc version this was added in. Seems fairly longstanding.
Seems to be already in 2.95, so every kernel compiler

IIRC, there had been some architectures where it didn't work correctly.
I don't remember details, though... Geert?

Andrew Morton

2013-08-07 23:54 UTC #4 lore raw

In reply to Andi Kleen

Quoted 7 lines · On Mon, 5 Aug 2013 15:09:35 -0700 Andi Kleen <[email protected]> wrote:

From: Andi Kleen <[email protected]>
Use standard gcc __attribute__((alias(foo))) to define the syscall aliases instead of custom assembler macros.
This is far cleaner, and also fixes my LTO kernel build.

This makes my x86_64 allmodconfig build emit screenfuls of

...
WARNING: "alloc_pages_current" [drivers/block/brd.ko] has no CRC!
WARNING: "alloc_pages_current" [drivers/base/firmware_class.ko] has no CRC!
WARNING: "schedule_timeout" [drivers/atm/solos-pci.ko] has no CRC!
WARNING: "schedule_timeout" [drivers/atm/iphase.ko] has no CRC!
WARNING: "schedule_timeout" [drivers/atm/he.ko] has no CRC!
WARNING: "schedule_timeout" [drivers/acpi/sbshc.ko] has no CRC!
WARNING: "schedule_timeout" [drivers/acpi/acpi_ipmi.ko] has no CRC!
WARNING: "alloc_pages_current" [crypto/async_tx/raid6test.ko] has no CRC!
WARNING: "alloc_pages_current" [crypto/async_tx/async_pq.ko] has no CRC!
WARNING: "alloc_pages_current" [crypto/algif_skcipher.ko] has no CRC!
WARNING: "schedule_timeout" [crypto/algif_skcipher.ko] has no CRC!
WARNING: "sock_register" [crypto/af_alg.ko] has no CRC!
WARNING: "task_nice" [block/cfq-iosched.ko] has no CRC!
WARNING: "perf_event_create_kernel_counter" [arch/x86/oprofile/oprofile.ko] has no CRC!
WARNING: "alloc_pages_current" [arch/x86/kvm/kvm.ko] has no CRC!
WARNING: "perf_event_create_kernel_counter" [arch/x86/kvm/kvm.ko] has no CRC!
WARNING: "alloc_pages_current" [arch/x86/kvm/kvm-amd.ko] has no CRC!
WARNING: "schedule_timeout" [arch/x86/kernel/cpu/mcheck/mce-inject.ko] has no CRC!
WARNING: "schedule_timeout" [arch/x86/kernel/apm.ko] has no CRC!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2

Unexpected, but I checked it a couple of times.

Andi Kleen

2013-08-08 04:39 UTC #5 lore raw

Quoted 11 lines · Andrew Morton

Quoted 7 lines · On Mon, 5 Aug 2013 15:09:35 -0700 Andi Kleen <[email protected]> wrote:
From: Andi Kleen <[email protected]>
Use standard gcc __attribute__((alias(foo))) to define the syscall aliases instead of custom assembler macros.
This is far cleaner, and also fixes my LTO kernel build.
This makes my x86_64 allmodconfig build emit screenfuls of

Ok I can reproduce with MODVERSIONS. Very mysterious, as I didn't change EXPORT_SYMBOL. Will look into it.

Thanks.

-Andi