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

Björn Töpel
2023-01-02T18:04:44Z

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.

> 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.

Björn