Messages in this thread | | | Date | Tue, 2 Mar 2021 09:06:47 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH 1/1] x86/kprobes: Use int3 instead of debug trap for single-step |
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On Mon, Mar 01, 2021 at 11:08:15PM +0900, Masami Hiramatsu wrote:
> +static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs) > +{ > + unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size; > + > + ip += p->ainsn.rel32; > + int3_emulate_jmp(regs, ip); > +} > +NOKPROBE_SYMBOL(kprobe_emulate_jmp);
Would it make sense to have this be something like:
static void kprobe_emulate_jmp(struct kprobe *p, struct pt_regs *regs, bool cond) { unsigned long ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
if (cond) ip += p->ainsn.rel32; int3_emulate_jmp(regs, ip); }
> +static void kprobe_emulate_jcc(struct kprobe *p, struct pt_regs *regs) > +{ > + bool invert = p->ainsn.jcc.type & 1; > + bool match; > + > + if (p->ainsn.jcc.type < 0xc) { > + match = regs->flags & jcc_mask[p->ainsn.jcc.type >> 1]; > + } else { > + match = ((regs->flags & X86_EFLAGS_SF) >> X86_EFLAGS_SF_BIT) ^ > + ((regs->flags & X86_EFLAGS_OF) >> X86_EFLAGS_OF_BIT); > + if (p->ainsn.jcc.type >= 0xe) > + match = match && (regs->flags & X86_EFLAGS_ZF); > + } > + if ((match && !invert) || (!match && invert)) > + kprobe_emulate_jmp(p, regs); > + else > + regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
Then you can do:
kprobe_emulate_jmp(p, regs, match);
> +} > +NOKPROBE_SYMBOL(kprobe_emulate_jcc); > + > +static void kprobe_emulate_loop(struct kprobe *p, struct pt_regs *regs) > +{ > + bool match; > + > + if (p->ainsn.loop.type != 3) { /* LOOP* */ > + if (p->ainsn.loop.asize == 32) > + match = ((*(u32 *)®s->cx)--) != 0; > +#ifdef CONFIG_X86_64 > + else if (p->ainsn.loop.asize == 64) > + match = ((*(u64 *)®s->cx)--) != 0; > +#endif > + else > + match = ((*(u16 *)®s->cx)--) != 0; > + } else { /* JCXZ */ > + if (p->ainsn.loop.asize == 32) > + match = *(u32 *)(®s->cx) == 0; > +#ifdef CONFIG_X86_64 > + else if (p->ainsn.loop.asize == 64) > + match = *(u64 *)(®s->cx) == 0; > +#endif > + else > + match = *(u16 *)(®s->cx) == 0; > + } > + > + if (p->ainsn.loop.type == 0) /* LOOPNE */ > + match = match && !(regs->flags & X86_EFLAGS_ZF); > + else if (p->ainsn.loop.type == 1) /* LOOPE */ > + match = match && (regs->flags & X86_EFLAGS_ZF); > + > + if (match) > + kprobe_emulate_jmp(p, regs); > + else > + regs->ip = regs->ip - INT3_INSN_SIZE + p->ainsn.size;
and here.
> +} > +NOKPROBE_SYMBOL(kprobe_emulate_loop);
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