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

Masami Hiramatsu
2021-05-25T14:45:15Z

Hi Jisheng,

On Wed, 12 May 2021 22:58:19 +0800
Jisheng Zhang <jszhang3@mail.ustc.edu.cn> wrote:

> 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.

As far as I compared with arm64 code, this looks good to me.

Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>

Thanks,

>
> 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;
> > }
> >
>
>

--
Masami Hiramatsu <mhiramat@kernel.org>