Re: [PATCH v5 1/9] riscv/kprobe: Prepare the skeleton to implement RISCV OPTPROBES feature

liaochang (A)
2023-01-04T08:44:04Z

在 2023/1/3 2:03, Björn Töpel 写道:
> Chen Guokai <chenguokai17@mails.ucas.ac.cn> writes:
>
>> From: Liao Chang <liaochang1@huawei.com>
>>
>> Prepare skeleton to implement optimized kprobe on RISCV, it is consist
>> of Makfile, Kconfig and some architecture specific files: kprobe.h and
>> opt.c opt.c include some macro, type definition and functions required
>> by kprobe framework, opt_trampoline.S provide a piece of assembly code
>> template used to construct the detour buffer as the target of long jump
>> instruction(s) for each optimzed kprobe.
>
> This is pretty much just reiterating what diff-stat says. Please try to
> explain why a certain change is done, instead of what. What is already
> in the patch.

Thanks for your suggestion, i will explain further in next revision.

>
>> Since the jump range of PC-relative instruction JAL is +/-2M, that is
>> too small to reach the detour buffer, hence the foudamental idea to
>> address OPTPROBES on RISCV is replace 'EBREAK' with 'AUIPC/JALR'. which
>> means it needs to clobber one more instruction beside the kprobe
>> instruction, furthermore, RISCV supports hybird RVI and RVC in single
>> kernel binary, so in theory a pair of 'AUIPC/JALR' is about to clobber
>> 10 bytes(3 RVC and 1 RVI, 2 bytes is padding for alignment) at worst
>> case. The second hardsome problem is looking for one integer register as
>> the destination of 'AUIPC/JALR' without any side-effect.
>
> There are a number of spelling errors, please use a spellchecker and if
> you reference a file (e.g. Makefile), make sure it is correctly spelled
> out.
>
> The comments above applies to all the commit messages of this series.

Thanks for reviewing, i will correct these spelling errors.

>
>
> Björn

--
BR,
Liao, Chang