Messages in this thread Patch in this message | | | Subject | Re: [PATCH v12 4/5] LoongArch: Mark some assembler symbols as non-kprobe-able | From | Jinyang He <> | Date | Wed, 18 Jan 2023 14:05:50 +0800 |
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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.
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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