Messages in this thread | | | From | Huacai Chen <> | Date | Wed, 18 Jan 2023 15:17:00 +0800 | Subject | Re: [PATCH v12 4/5] LoongArch: Mark some assembler symbols as non-kprobe-able |
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On Wed, Jan 18, 2023 at 2:24 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote: > > > > 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" Then, why is handle_syscall different from other exception handlers?
Huacai > > > > > 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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