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Re: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover instructions on optimized path
- From: Ingo Molnar <mingo at elte dot hu>
- To: Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>
- Cc: linux-kernel at vger dot kernel dot org, yrl dot pp-manager dot tt at hitachi dot com, systemtap at sourceware dot org, anderson at redhat dot com, Thomas Gleixner <tglx at linutronix dot de>, "H. Peter Anvin" <hpa at zytor dot com>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>
- Date: Mon, 27 Feb 2012 10:34:21 +0100
- Subject: Re: [PATCH v3 -tip] [BUGFIX] x86/kprobes: Fix to recover instructions on optimized path
- References: <20120223083703.GA26781@elte.hu> <20120224095412.8462.55698.stgit@localhost.localdomain>
* Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> wrote:
> +
> +#ifdef CONFIG_OPTPROBES
> +static unsigned long __recover_optprobed_insn(struct kprobe *kp,
> + kprobe_opcode_t *buf,
> + unsigned long addr)
> +{
> + long offs = addr - (unsigned long)kp->addr - 1;
> + struct optimized_kprobe *op = container_of(kp, struct optimized_kprobe, kp);
> +
> + /*
> + * If the kprobe can be optimized, original bytes which can be
> + * overwritten by jump destination address. In this case, original
> + * bytes must be recovered from op->optinsn.copied_insn buffer.
> + */
> + memcpy(buf, (void *)addr, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
> + if (addr == (unsigned long)kp->addr) {
> + buf[0] = kp->opcode;
> + memcpy(buf + 1, op->optinsn.copied_insn, RELATIVE_ADDR_SIZE);
> + } else
> + memcpy(buf, op->optinsn.copied_insn + offs, RELATIVE_ADDR_SIZE - offs);
> +
> + return (unsigned long)buf;
> +}
> +#endif
Why not stick this into a new kprobes-opt.c file?
> +
> +/*
> + * Recover the probed instruction at addr for further analysis.
> + * Caller must lock kprobes by kprobe_mutex, or disable preemption
> + * for preventing to release referencing kprobes.
> + */
> +static unsigned long recover_probed_instruction(kprobe_opcode_t *buf,
> + unsigned long addr)
> +{
> + struct kprobe *kp;
> +#ifdef CONFIG_OPTPROBES
> + int i;
> +
> + for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
> + kp = get_kprobe((void *)addr - i);
> + if (kp && kprobe_optready(kp))
> + return __recover_optprobed_insn(kp, buf, addr);
> + }
> +#endif
This should be a separate, kprobes_recover_opt() method and be
inside kprobes-opt.c as well.
Thanks,
Ingo