linux-kernel - Re: [PATCH v6 07/13] riscv/kprobe: Prepare detour buffer for optimized kprobe

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Date:   Wed, 01 Feb 2023 14:30:28 +0100
From:   Björn Töpel <bjorn@...nel.org>
To:     Chen Guokai <chenguokai17@...ls.ucas.ac.cn>,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, rostedt@...dmis.org, mingo@...hat.com,
        sfr@...b.auug.org.au
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        liaochang1@...wei.com, Chen Guokai <chenguokai17@...ls.ucas.ac.cn>
Subject: Re: [PATCH v6 07/13] riscv/kprobe: Prepare detour buffer for
 optimized kprobe

Chen Guokai <chenguokai17@...ls.ucas.ac.cn> writes:

> diff --git a/arch/riscv/kernel/probes/opt.c b/arch/riscv/kernel/probes/opt.c
> index d84aa1420fa2..a47f7d2bf3a6 100644
> --- a/arch/riscv/kernel/probes/opt.c
> +++ b/arch/riscv/kernel/probes/opt.c
> @@ -11,9 +11,32 @@
>  #include <linux/kprobes.h>
>  #include <asm/kprobes.h>
>  #include <asm/patch.h>
> +#include <asm/asm-offsets.h>
>  
>  #include "simulate-insn.h"
>  #include "decode-insn.h"
> +#include "../../net/bpf_jit.h"
> +
> +static void optimized_callback(struct optimized_kprobe *op,
> +			       struct pt_regs *regs)
> +{
> +	if (kprobe_disabled(&op->kp))
> +		return;
> +
> +	preempt_disable();
> +	if (kprobe_running()) {
> +		kprobes_inc_nmissed_count(&op->kp);
> +	} else {
> +		__this_cpu_write(current_kprobe, &op->kp);
> +		/* Save skipped registers */
> +		instruction_pointer_set(regs, (unsigned long)op->kp.addr);
> +		get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;
> +		opt_pre_handler(&op->kp, regs);
> +		__this_cpu_write(current_kprobe, NULL);
> +	}
> +	preempt_enable();
> +}
> +NOKPROBE_SYMBOL(optimized_callback)
>  
>  static int in_auipc_jalr_range(long val)
>  {
> @@ -30,6 +53,11 @@ static int in_auipc_jalr_range(long val)
>  #endif
>  }
>  
> +#define DETOUR_ADDR(code, offs) \
> +	((void *)((unsigned long)(code) + (offs)))
> +#define DETOUR_INSN(code, offs) \
> +	(*(kprobe_opcode_t *)((unsigned long)(code) + (offs)))

Can this cause a misaligned u32 load exception?


Björn