* [PATCH] x86/vdso: fix lsl operand order
@ 2018-09-01 7:27 Samuel Neves
2018-09-01 11:00 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Samuel Neves @ 2018-09-01 7:27 UTC (permalink / raw)
To: Thomas Gleixner, Ingo Molnar; +Cc: x86, stable, Samuel Neves
In the __getcpu function, lsl was using the wrong target
and destination registers. Luckily, the compiler tends to
choose %eax for both variables, so it has been working
so far.
Signed-off-by: Samuel Neves <sneves@dei.uc.pt>
---
arch/x86/include/asm/vgtod.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index fb856c9f0449..53748541c487 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -93,7 +93,7 @@ static inline unsigned int __getcpu(void)
*
* If RDPID is available, use it.
*/
- alternative_io ("lsl %[p],%[seg]",
+ alternative_io ("lsl %[seg],%[p]",
".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
X86_FEATURE_RDPID,
[p] "=a" (p), [seg] "r" (__PER_CPU_SEG));
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] x86/vdso: fix lsl operand order
2018-09-01 7:27 [PATCH] x86/vdso: fix lsl operand order Samuel Neves
@ 2018-09-01 11:00 ` Greg KH
0 siblings, 0 replies; 4+ messages in thread
From: Greg KH @ 2018-09-01 11:00 UTC (permalink / raw)
To: Samuel Neves; +Cc: Thomas Gleixner, Ingo Molnar, x86, stable
On Sat, Sep 01, 2018 at 08:27:35AM +0100, Samuel Neves wrote:
> In the __getcpu function, lsl was using the wrong target
> and destination registers. Luckily, the compiler tends to
> choose %eax for both variables, so it has been working
> so far.
>
> Signed-off-by: Samuel Neves <sneves@dei.uc.pt>
> ---
> arch/x86/include/asm/vgtod.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] x86/vdso: fix lsl operand order
@ 2018-09-01 20:14 Samuel Neves
2018-09-01 20:43 ` Andy Lutomirski
0 siblings, 1 reply; 4+ messages in thread
From: Samuel Neves @ 2018-09-01 20:14 UTC (permalink / raw)
To: Andy Lutomirski, linux-kernel; +Cc: Samuel Neves, x86, stable
In the __getcpu function, lsl was using the wrong target
and destination registers. Luckily, the compiler tends to
choose %eax for both variables, so it has been working
so far.
Cc: x86@kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Samuel Neves <sneves@dei.uc.pt>
---
arch/x86/include/asm/vgtod.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index fb856c9f0449..53748541c487 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -93,7 +93,7 @@ static inline unsigned int __getcpu(void)
*
* If RDPID is available, use it.
*/
- alternative_io ("lsl %[p],%[seg]",
+ alternative_io ("lsl %[seg],%[p]",
".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
X86_FEATURE_RDPID,
[p] "=a" (p), [seg] "r" (__PER_CPU_SEG));
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] x86/vdso: fix lsl operand order
2018-09-01 20:14 Samuel Neves
@ 2018-09-01 20:43 ` Andy Lutomirski
0 siblings, 0 replies; 4+ messages in thread
From: Andy Lutomirski @ 2018-09-01 20:43 UTC (permalink / raw)
To: Samuel Neves; +Cc: Andy Lutomirski, LKML, X86 ML, stable
On Sat, Sep 1, 2018 at 1:14 PM, Samuel Neves <sneves@dei.uc.pt> wrote:
> In the __getcpu function, lsl was using the wrong target
> and destination registers. Luckily, the compiler tends to
> choose %eax for both variables, so it has been working
> so far.
>
> Cc: x86@kernel.org
> Cc: stable@vger.kernel.org
> Signed-off-by: Samuel Neves <sneves@dei.uc.pt>
Acked-by: Andy Lutomirski <luto@kernel.org>
Fixes: a582c540ac1b ("x86/vdso: Use RDPID in preference to LSL when available")
Whoops! I even wrote a selftest just for the offending commit, but,
of course, the selftest passes :( I tested this by giving gcc some
gentle encouragement to allocate different registers, and the existing
code is indeed wrong and the fix indeed fixes it.
--Andy
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2018-09-02 0:57 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2018-09-01 7:27 [PATCH] x86/vdso: fix lsl operand order Samuel Neves
2018-09-01 11:00 ` Greg KH
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2018-09-01 20:14 Samuel Neves
2018-09-01 20:43 ` Andy Lutomirski
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