* [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
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