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

Palmer Dabbelt
2021-05-29T18:40:47Z

On Wed, 12 May 2021 07:58:19 PDT (-0700), 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.

Sorry, I missed this one. This is on for-next.

>
> 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;
>> }
>>