Re: [PATCH] riscv: kprobes: Remove redundant kprobe_step_ctx

Jisheng Zhang
2021-05-12T15:29:23Z

On Mon, 19 Apr 2021 00:29:19 +0800
Jisheng Zhang <jszhang3@mail.ustc.edu.cn> wrote:

> From: Jisheng Zhang <jszhang@kernel.org>
>
> Inspired by commit ba090f9cafd5 ("arm64: kprobes: Remove redundant
> kprobe_step_ctx"), the ss_pending and match_addr of kprobe_step_ctx
> are redundant because those can be replaced by KPROBE_HIT_SS and
> &cur_kprobe->ainsn.api.insn[0] + GET_INSN_LENGTH(cur->opcode)
> respectively.
>
> Remove the kprobe_step_ctx to simplify the code.

Hi all,

This patch can still be applied to 5.13-rc1, could you please review? Let me
know if a rebase on 5.13-rc1 is needed.

Thanks

>
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> arch/riscv/include/asm/kprobes.h | 7 ------
> arch/riscv/kernel/probes/kprobes.c | 40 +++++++-----------------------
> 2 files changed, 9 insertions(+), 38 deletions(-)
>
> diff --git a/arch/riscv/include/asm/kprobes.h b/arch/riscv/include/asm/kprobes.h
> index 4647d38018f6..9ea9b5ec3113 100644
> --- a/arch/riscv/include/asm/kprobes.h
> +++ b/arch/riscv/include/asm/kprobes.h
> @@ -29,18 +29,11 @@ struct prev_kprobe {
> unsigned int status;
> };
>
> -/* Single step context for kprobe */
> -struct kprobe_step_ctx {
> - unsigned long ss_pending;
> - unsigned long match_addr;
> -};
> -
> /* per-cpu kprobe control block */
> struct kprobe_ctlblk {
> unsigned int kprobe_status;
> unsigned long saved_status;
> struct prev_kprobe prev_kprobe;
> - struct kprobe_step_ctx ss_ctx;
> };
>
> void arch_remove_kprobe(struct kprobe *p);
> diff --git a/arch/riscv/kernel/probes/kprobes.c b/arch/riscv/kernel/probes/kprobes.c
> index 8c1f7a30aeed..4c1ad5536748 100644
> --- a/arch/riscv/kernel/probes/kprobes.c
> +++ b/arch/riscv/kernel/probes/kprobes.c
> @@ -17,7 +17,7 @@ DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
> DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
>
> static void __kprobes
> -post_kprobe_handler(struct kprobe_ctlblk *, struct pt_regs *);
> +post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *);
>
> static void __kprobes arch_prepare_ss_slot(struct kprobe *p)
> {
> @@ -43,7 +43,7 @@ static void __kprobes arch_simulate_insn(struct kprobe *p, struct pt_regs *regs)
> p->ainsn.api.handler((u32)p->opcode,
> (unsigned long)p->addr, regs);
>
> - post_kprobe_handler(kcb, regs);
> + post_kprobe_handler(p, kcb, regs);
> }
>
> int __kprobes arch_prepare_kprobe(struct kprobe *p)
> @@ -149,21 +149,6 @@ static void __kprobes kprobes_restore_local_irqflag(struct kprobe_ctlblk *kcb,
> regs->status = kcb->saved_status;
> }
>
> -static void __kprobes
> -set_ss_context(struct kprobe_ctlblk *kcb, unsigned long addr, struct kprobe *p)
> -{
> - unsigned long offset = GET_INSN_LENGTH(p->opcode);
> -
> - kcb->ss_ctx.ss_pending = true;
> - kcb->ss_ctx.match_addr = addr + offset;
> -}
> -
> -static void __kprobes clear_ss_context(struct kprobe_ctlblk *kcb)
> -{
> - kcb->ss_ctx.ss_pending = false;
> - kcb->ss_ctx.match_addr = 0;
> -}
> -
> static void __kprobes setup_singlestep(struct kprobe *p,
> struct pt_regs *regs,
> struct kprobe_ctlblk *kcb, int reenter)
> @@ -182,8 +167,6 @@ static void __kprobes setup_singlestep(struct kprobe *p,
> /* prepare for single stepping */
> slot = (unsigned long)p->ainsn.api.insn;
>
> - set_ss_context(kcb, slot, p); /* mark pending ss */
> -
> /* IRQs and single stepping do not mix well. */
> kprobes_save_local_irqflag(kcb, regs);
>
> @@ -219,13 +202,8 @@ static int __kprobes reenter_kprobe(struct kprobe *p,
> }
>
> static void __kprobes
> -post_kprobe_handler(struct kprobe_ctlblk *kcb, struct pt_regs *regs)
> +post_kprobe_handler(struct kprobe *cur, struct kprobe_ctlblk *kcb, struct pt_regs *regs)
> {
> - struct kprobe *cur = kprobe_running();
> -
> - if (!cur)
> - return;
> -
> /* return addr restore if non-branching insn */
> if (cur->ainsn.api.restore != 0)
> regs->epc = cur->ainsn.api.restore;
> @@ -355,16 +333,16 @@ bool __kprobes
> kprobe_single_step_handler(struct pt_regs *regs)
> {
> struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
> + unsigned long addr = instruction_pointer(regs);
> + struct kprobe *cur = kprobe_running();
>
> - if ((kcb->ss_ctx.ss_pending)
> - && (kcb->ss_ctx.match_addr == instruction_pointer(regs))) {
> - clear_ss_context(kcb); /* clear pending ss */
> -
> + if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) &&
> + ((unsigned long)&cur->ainsn.api.insn[0] + GET_INSN_LENGTH(cur->opcode) == addr)) {
> kprobes_restore_local_irqflag(kcb, regs);
> -
> - post_kprobe_handler(kcb, regs);
> + post_kprobe_handler(cur, kcb, regs);
> return true;
> }
> + /* not ours, kprobes should ignore it */
> return false;
> }
>