[PATCH] riscv: kprobes: Remove redundant kprobe_step_ctx

Jisheng Zhang
2021-04-18T16:34:40Z

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.

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;
}

--
2.31.0