[PATCH] x86: vget_cycles() __always_inline

[PATCH] x86: vget_cycles() __always_inline

[Hugh Dickins]

Mark vget_cycles() as __always_inline, so gcc is never tempted to make
the vsyscall vread_tsc() dive into kernel text, with resulting SIGSEGV.

This was a self-inflicted wound: I've not seen that happen with unhacked
sources; but for debug reasons I'd changed my x86/Makefile to compile
no-unit-at-a-time, and that in conjunction with OPTIMIZE_INLINING=y
ended up with vget_cycles() in kernel text.  Perhaps it can happen
in other ways: safer to use __always_inline.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
---

 include/asm-x86/tsc.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 2.6.25-mm1/include/asm-x86/tsc.h	2008-04-18 12:18:34.000000000 +0100
+++ linux/include/asm-x86/tsc.h	2008-04-24 19:12:32.000000000 +0100
@@ -32,7 +32,7 @@ static inline cycles_t get_cycles(void)
 	return ret;
 }
 
-static inline cycles_t vget_cycles(void)
+static __always_inline cycles_t vget_cycles(void)
 {
 	/*
 	 * We only do VDSOs on TSC capable CPUs, so this shouldnt

Re: [PATCH] x86: vget_cycles() __always_inline

[Ingo Molnar]

* Hugh Dickins <hugh@veritas.com> wrote:

> Mark vget_cycles() as __always_inline, so gcc is never tempted to make 
> the vsyscall vread_tsc() dive into kernel text, with resulting 
> SIGSEGV.
> 
> This was a self-inflicted wound: I've not seen that happen with 
> unhacked sources; but for debug reasons I'd changed my x86/Makefile to 
> compile no-unit-at-a-time, and that in conjunction with 
> OPTIMIZE_INLINING=y ended up with vget_cycles() in kernel text.  
> Perhaps it can happen in other ways: safer to use __always_inline.

applied, thanks Hugh - i agree that this is worth fixing.

	Ingo