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Subject: Re: [PATCH] LoongArch/rethook: Replace kretprobe with rethook on
 loongarch
To:     jianghaoran <jianghaoran@kylinos.cn>, chenhuacai@kernel.org
References: <20230612054949.305652-1-jianghaoran@kylinos.cn>
Cc:     kernel@xen0n.name, zhangqing@loongson.cn, hejinyang@loongson.cn,
        tangyouling@loongson.cn, masahiroy@kernel.org,
        conor.dooley@microchip.com, l3b2w1@gmail.com, palmer@rivosinc.com,
        mhiramat@kernel.org, loongarch@lists.linux.dev,
        linux-kernel@vger.kernel.org, jhrhhao <jhrhhao@163.com>
From:   Tiezhu Yang <yangtiezhu@loongson.cn>
Message-ID: <63c16a5a-ea60-6607-a4ff-23ad9d47cd73@loongson.cn>
Date:   Mon, 12 Jun 2023 15:26:31 +0800
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On 06/12/2023 01:49 PM, jianghaoran wrote:
> That's an adaptation of commit f3a112c0c40d ("x86,rethook,kprobes:
> Replace kretprobe with rethook on x86") to loongarch.
>
> Replaces the kretprobe code with rethook on loongarch. With this patch,
> kretprobe on loongarch uses the rethook instead of kretprobe specific
> trampoline code.
>
> Signed-off-by: jianghaoran<jianghaoran@kylinos.cn>
> Signed-off-by: jhrhhao<jhrhhao@163.com>

Please check Signed-off-by's "<first> <last> <email>" order
and spelling. Should it be "Haoran Jiang <jianghaoran@kylinos.cn>"?
Please refer the following link:
https://lore.kernel.org/all/CAEf4BzYS5mj+0ZBA2HKW3=kB1cjZ3wdiJZ2OP9gSLE4e7WB_wQ@mail.gmail.com/

> ---
>  arch/loongarch/Kconfig                        |  1 +
>  arch/loongarch/include/asm/kprobes.h          |  3 ---
>  arch/loongarch/kernel/Makefile                |  3 ++-
>  arch/loongarch/kernel/kprobes.c               | 20 --------------
>  arch/loongarch/kernel/rethook.c               | 27 +++++++++++++++++++
>  arch/loongarch/kernel/rethook.h               |  9 +++++++
>  ...obes_trampoline.S => rethook_trampoline.S} |  6 ++---
>  7 files changed, 42 insertions(+), 27 deletions(-)
>  create mode 100644 arch/loongarch/kernel/rethook.c
>  create mode 100644 arch/loongarch/kernel/rethook.h
>  rename arch/loongarch/kernel/{kprobes_trampoline.S => rethook_trampoline.S} (93%)

...

> --- a/arch/loongarch/kernel/kprobes.c
> +++ b/arch/loongarch/kernel/kprobes.c
> @@ -378,26 +378,6 @@ int __init arch_init_kprobes(void)
>  	return 0;
>  }
>
> -/* ASM function that handles the kretprobes must not be probed */
> -NOKPROBE_SYMBOL(__kretprobe_trampoline);
> -
> -/* Called from __kretprobe_trampoline */
> -void __used *trampoline_probe_handler(struct pt_regs *regs)
> -{
> -	return (void *)kretprobe_trampoline_handler(regs, NULL);
> -}
> -NOKPROBE_SYMBOL(trampoline_probe_handler);
> -
> -void arch_prepare_kretprobe(struct kretprobe_instance *ri,
> -			    struct pt_regs *regs)
> -{
> -	ri->ret_addr = (kprobe_opcode_t *)regs->regs[1];
> -	ri->fp = NULL;
> -
> -	/* Replace the return addr with trampoline addr */
> -	regs->regs[1] = (unsigned long)&__kretprobe_trampoline;
> -}
> -NOKPROBE_SYMBOL(arch_prepare_kretprobe);
>

When git am this patch, there exists the following warning:

Applying: LoongArch/rethook: Replace kretprobe with rethook on loongarch
.git/rebase-apply/patch:131: new blank line at EOF.
+
warning: 1 line adds whitespace errors.

So please remove the blank line.

>  int arch_trampoline_kprobe(struct kprobe *p)

...

> -SYM_CODE_END(__kretprobe_trampoline)
> +SYM_CODE_END(arch_rethook_trampoline)

This patch is almost same with commit b57c2f124098 ("riscv: add
riscv rethook implementation"), it is better to provide this info
in the commit message.

The code itself looks good to me, I am doing the test.

Thanks,
Tiezhu