linux-kernel - [PATCH] x86: vget_cycles() __always

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Date:	Sun, 27 Apr 2008 00:39:36 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Ingo Molnar <mingo@...e.hu>
cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] x86: vget_cycles() __always_inline

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@...itas.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
--
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