* [PATCH] MIPS: fix kernel_stack_pointer()
@ 2021-01-29 4:35 Huang Pei
2021-02-01 12:23 ` Thomas Bogendoerfer
0 siblings, 1 reply; 4+ messages in thread
From: Huang Pei @ 2021-01-29 4:35 UTC (permalink / raw)
To: Thomas Bogendoerfer, ambrosehua
Cc: Bibo Mao, Andrew Morton, linux-mips, linux-arch, linux-mm,
Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu, Gao Juxin,
Fuxin Zhang, Huacai Chen
MIPS always save kernel stack pointer in regs[29]
Signed-off-by: Huang Pei <huangpei@loongson.cn>
---
arch/mips/include/asm/ptrace.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
index 1e76774b36dd..daf3cf244ea9 100644
--- a/arch/mips/include/asm/ptrace.h
+++ b/arch/mips/include/asm/ptrace.h
@@ -53,7 +53,7 @@ struct pt_regs {
static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
{
- return regs->regs[31];
+ return regs->regs[29];
}
static inline void instruction_pointer_set(struct pt_regs *regs,
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] MIPS: fix kernel_stack_pointer()
2021-01-29 4:35 [PATCH] MIPS: fix kernel_stack_pointer() Huang Pei
@ 2021-02-01 12:23 ` Thomas Bogendoerfer
2021-02-02 1:32 ` Huang Pei
0 siblings, 1 reply; 4+ messages in thread
From: Thomas Bogendoerfer @ 2021-02-01 12:23 UTC (permalink / raw)
To: Huang Pei
Cc: ambrosehua, Bibo Mao, Andrew Morton, linux-mips, linux-arch,
linux-mm, Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu,
Gao Juxin, Fuxin Zhang, Huacai Chen
On Fri, Jan 29, 2021 at 12:35:07PM +0800, Huang Pei wrote:
> MIPS always save kernel stack pointer in regs[29]
>
> Signed-off-by: Huang Pei <huangpei@loongson.cn>
> ---
> arch/mips/include/asm/ptrace.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
> index 1e76774b36dd..daf3cf244ea9 100644
> --- a/arch/mips/include/asm/ptrace.h
> +++ b/arch/mips/include/asm/ptrace.h
> @@ -53,7 +53,7 @@ struct pt_regs {
>
> static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
> {
> - return regs->regs[31];
> + return regs->regs[29];
hmm, I'm still wondering where the trick is... looks like this is used
for uprobes, so nobody has ever used uprobes or I'm missing something.
How did you find that ?
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] MIPS: fix kernel_stack_pointer()
2021-02-01 12:23 ` Thomas Bogendoerfer
@ 2021-02-02 1:32 ` Huang Pei
2021-02-03 10:36 ` Thomas Bogendoerfer
0 siblings, 1 reply; 4+ messages in thread
From: Huang Pei @ 2021-02-02 1:32 UTC (permalink / raw)
To: Thomas Bogendoerfer
Cc: ambrosehua, Bibo Mao, Andrew Morton, linux-mips, linux-arch,
linux-mm, Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu,
Gao Juxin, Fuxin Zhang, Huacai Chen
On Mon, Feb 01, 2021 at 01:23:52PM +0100, Thomas Bogendoerfer wrote:
> On Fri, Jan 29, 2021 at 12:35:07PM +0800, Huang Pei wrote:
> > MIPS always save kernel stack pointer in regs[29]
> >
> > Signed-off-by: Huang Pei <huangpei@loongson.cn>
> > ---
> > arch/mips/include/asm/ptrace.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
> > index 1e76774b36dd..daf3cf244ea9 100644
> > --- a/arch/mips/include/asm/ptrace.h
> > +++ b/arch/mips/include/asm/ptrace.h
> > @@ -53,7 +53,7 @@ struct pt_regs {
> >
> > static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
> > {
> > - return regs->regs[31];
> > + return regs->regs[29];
>
> hmm, I'm still wondering where the trick is... looks like this is used
> for uprobes, so nobody has ever used uprobes or I'm missing something.
>
> How did you find that ?
>
> Thomas.
>
> --
> Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
> good idea. [ RFC1925, 2.3 ]
Long story for short,
+. I think I had fix this bug in 2018, when I backported Uprobe from my
4.4 branch to CentOS 7 3.10. I just knwo it is *not* following MIPS
ABI, but I do not know how it destroy the cool function of
Kprobe/Uprobe, since the failure in porting eBPF from upstream to 3.10
just leave the fix in 3.10, totally forgotten.
+. In 2020, I was told to validate the effect of GNU XHash, and it came
to me that using Uprobe to count the number of "strcmp" called in ld.so,
so I found this fix again.
+. With more work on Kprobe/Kprobe_event/Uprobe, I found it hit only when
accessing arguments of Kprobe/Uprobe, so simple counting numbers of probe
fired would not trigger it
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] MIPS: fix kernel_stack_pointer()
2021-02-02 1:32 ` Huang Pei
@ 2021-02-03 10:36 ` Thomas Bogendoerfer
0 siblings, 0 replies; 4+ messages in thread
From: Thomas Bogendoerfer @ 2021-02-03 10:36 UTC (permalink / raw)
To: Huang Pei
Cc: ambrosehua, Bibo Mao, Andrew Morton, linux-mips, linux-arch,
linux-mm, Jiaxun Yang, Paul Burton, Li Xuefeng, Yang Tiezhu,
Gao Juxin, Fuxin Zhang, Huacai Chen
On Tue, Feb 02, 2021 at 09:32:31AM +0800, Huang Pei wrote:
> On Mon, Feb 01, 2021 at 01:23:52PM +0100, Thomas Bogendoerfer wrote:
> > On Fri, Jan 29, 2021 at 12:35:07PM +0800, Huang Pei wrote:
> > > MIPS always save kernel stack pointer in regs[29]
> > >
> > > Signed-off-by: Huang Pei <huangpei@loongson.cn>
> > > ---
> > > arch/mips/include/asm/ptrace.h | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/mips/include/asm/ptrace.h b/arch/mips/include/asm/ptrace.h
> > > index 1e76774b36dd..daf3cf244ea9 100644
> > > --- a/arch/mips/include/asm/ptrace.h
> > > +++ b/arch/mips/include/asm/ptrace.h
> > > @@ -53,7 +53,7 @@ struct pt_regs {
> > >
> > > static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
> > > {
> > > - return regs->regs[31];
> > > + return regs->regs[29];
> >
> > hmm, I'm still wondering where the trick is... looks like this is used
> > for uprobes, so nobody has ever used uprobes or I'm missing something.
> >
> > How did you find that ?
> >
> > Thomas.
> >
> > --
> > Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
> > good idea. [ RFC1925, 2.3 ]
>
>
> Long story for short,
>
> +. I think I had fix this bug in 2018, when I backported Uprobe from my
> 4.4 branch to CentOS 7 3.10. I just knwo it is *not* following MIPS
> ABI, but I do not know how it destroy the cool function of
> Kprobe/Uprobe, since the failure in porting eBPF from upstream to 3.10
> just leave the fix in 3.10, totally forgotten.
>
> +. In 2020, I was told to validate the effect of GNU XHash, and it came
> to me that using Uprobe to count the number of "strcmp" called in ld.so,
> so I found this fix again.
>
> +. With more work on Kprobe/Kprobe_event/Uprobe, I found it hit only when
> accessing arguments of Kprobe/Uprobe, so simple counting numbers of probe
> fired would not trigger it
Thank you for the explanation, applied to mips-next.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-02-03 10:40 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-01-29 4:35 [PATCH] MIPS: fix kernel_stack_pointer() Huang Pei
2021-02-01 12:23 ` Thomas Bogendoerfer
2021-02-02 1:32 ` Huang Pei
2021-02-03 10:36 ` Thomas Bogendoerfer
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).