Re: [RFC PATCH 1/1] x86/kprobes: Use int3 instead of debug trap for single-step

[Peter Zijlstra]

On Tue, Mar 02, 2021 at 09:54:43AM +0100, Peter Zijlstra wrote:


> +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);
> +     }
> +     __kprobe_emulate_jmp(p, regs, (match && !invert) || (!match && invert));

Also, isn't that: 'match ^ invert' ?

> +}