Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH v12 4/5] LoongArch: Mark some assembler symbols as non-kprobe-able | From | Jinyang He <> | Date | Wed, 18 Jan 2023 15:20:38 +0800 |
| |
On 2023-01-18 14:24, Tiezhu Yang 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"
Okay, I can reproduce the hang, but sometimes quickly while sometimes slowly. I do not know why it happend. Can you explain how recursion happens? I means, can you explain why
no need mark {vprintk_store, vprintk, ... } as it may also cause recursion.
> >> >> 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 >>>>> >>>
| ![\](/images/icornerr.gif) |