Messages in this thread | | | Subject | Re: [PATCH v12 4/5] LoongArch: Mark some assembler symbols as non-kprobe-able | From | Tiezhu Yang <> | Date | Wed, 18 Jan 2023 14:24:46 +0800 |
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On 01/18/2023 02:05 PM, Jinyang He wrote: > > On 2023-01-18 12:23, Tiezhu Yang wrote: >> >> >> On 01/18/2023 12:14 PM, Huacai Chen wrote: >>> If memcpy should be blacklisted, then what about memset and memmove? >> >> According to the test results, there are no problems to probe >> memset and memmove, so no need to blacklist them for now, >> blacklist memcpy is because it may cause recursive exceptions, >> there is a detailed discussion in the following link: >> >> https://lore.kernel.org/lkml/20230114143859.7ccc45c1c5d9ce302113ab0a@kernel.org/ >> > > Hi, Tiezhu, > > I cannot reproduce the results when kprobe memcpy. Could you please give > some details. Emm, I just replace "kernel_clone" with "memcpy" in > kprobe_example.c.
Please remove the related "_ASM_NOKPROBE(memcpy)" code in arch/loongarch/lib/memcpy.S, and then compile and update kernel, execute the following cmd after reboot, I can reproduce the hang problem easily (it will take a few minutes).
modprobe kprobe_example symbol="memcpy"
> > And for your call trace, > > handler_pre() > pr_info() > printk() > _printk() > vprintk() > vprintk_store() > memcpy() > > I think when we should skip this time kprobe which triggered in > handler_{pre, post}. That means this time kprobe will not call > handler_{pre, post} agian, and not cause recursion. I remember > your codes had done this skip action. So, that's so strange if > recursion in handler_{pre, post}. > > > Thanks, > > Jinyang > > >> >> Thanks, >> Tiezhu >> >>> >>> Huacai >>> >>> On Wed, Jan 18, 2023 at 10:01 AM Tiezhu Yang <yangtiezhu@loongson.cn> >>> wrote: >>>> >>>> Some assembler symbols are not kprobe safe, such as handle_syscall >>>> (used as syscall exception handler), *memcpy* (may cause recursive >>>> exceptions), they can not be instrumented, just blacklist them for >>>> kprobing. >>>> >>>> Here is a related problem and discussion: >>>> Link: >>>> https://lore.kernel.org/lkml/20230114143859.7ccc45c1c5d9ce302113ab0a@kernel.org/ >>>> >>>> >>>> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> >>>> --- >>>> arch/loongarch/include/asm/asm.h | 10 ++++++++++ >>>> arch/loongarch/kernel/entry.S | 1 + >>>> arch/loongarch/lib/memcpy.S | 3 +++ >>>> 3 files changed, 14 insertions(+) >>>> >>>> diff --git a/arch/loongarch/include/asm/asm.h >>>> b/arch/loongarch/include/asm/asm.h >>>> index 40eea6a..f591b32 100644 >>>> --- a/arch/loongarch/include/asm/asm.h >>>> +++ b/arch/loongarch/include/asm/asm.h >>>> @@ -188,4 +188,14 @@ >>>> #define PTRLOG 3 >>>> #endif >>>> >>>> +/* Annotate a function as being unsuitable for kprobes. */ >>>> +#ifdef CONFIG_KPROBES >>>> +#define _ASM_NOKPROBE(name) \ >>>> + .pushsection "_kprobe_blacklist", "aw"; \ >>>> + .quad name; \ >>>> + .popsection >>>> +#else >>>> +#define _ASM_NOKPROBE(name) >>>> +#endif >>>> + >>>> #endif /* __ASM_ASM_H */ >>>> diff --git a/arch/loongarch/kernel/entry.S >>>> b/arch/loongarch/kernel/entry.S >>>> index d53b631..55e23b1 100644 >>>> --- a/arch/loongarch/kernel/entry.S >>>> +++ b/arch/loongarch/kernel/entry.S >>>> @@ -67,6 +67,7 @@ SYM_FUNC_START(handle_syscall) >>>> >>>> RESTORE_ALL_AND_RET >>>> SYM_FUNC_END(handle_syscall) >>>> +_ASM_NOKPROBE(handle_syscall) >>>> >>>> SYM_CODE_START(ret_from_fork) >>>> bl schedule_tail # a0 = struct task_struct *prev >>>> diff --git a/arch/loongarch/lib/memcpy.S b/arch/loongarch/lib/memcpy.S >>>> index 7c07d59..3b7e1de 100644 >>>> --- a/arch/loongarch/lib/memcpy.S >>>> +++ b/arch/loongarch/lib/memcpy.S >>>> @@ -17,6 +17,7 @@ SYM_FUNC_START(memcpy) >>>> ALTERNATIVE "b __memcpy_generic", \ >>>> "b __memcpy_fast", CPU_FEATURE_UAL >>>> SYM_FUNC_END(memcpy) >>>> +_ASM_NOKPROBE(memcpy) >>>> >>>> EXPORT_SYMBOL(memcpy) >>>> >>>> @@ -41,6 +42,7 @@ SYM_FUNC_START(__memcpy_generic) >>>> 2: move a0, a3 >>>> jr ra >>>> SYM_FUNC_END(__memcpy_generic) >>>> +_ASM_NOKPROBE(__memcpy_generic) >>>> >>>> /* >>>> * void *__memcpy_fast(void *dst, const void *src, size_t n) >>>> @@ -93,3 +95,4 @@ SYM_FUNC_START(__memcpy_fast) >>>> 3: move a0, a3 >>>> jr ra >>>> SYM_FUNC_END(__memcpy_fast) >>>> +_ASM_NOKPROBE(__memcpy_fast) >>>> -- >>>> 2.1.0 >>>> >>
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