Re: [PATCH V5 05/13] perf/x86: Add perf text poke events for kprobes

Masami Hiramatsu
2020-03-31T23:44:18Z

On Fri, 27 Mar 2020 10:36:09 +0200
Adrian Hunter <adrian.hunter@intel.com> wrote:

> Add perf text poke events for kprobes. That includes:
>
> - the replaced instruction(s) which are executed out-of-line
> i.e. arch_copy_kprobe() and arch_remove_kprobe()
>
> - optimised kprobe function
> i.e. arch_prepare_optimized_kprobe() and
> __arch_remove_optimized_kprobe()
>
> - optimised kprobe
> i.e. arch_optimize_kprobes() and arch_unoptimize_kprobe()
>
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>

This looks good to me.

Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

Thank you!

> ---
>
>
> Changes in V5:
>
> Simplify optimized kprobes events (Peter)
>
>
> arch/x86/include/asm/kprobes.h | 2 ++
> arch/x86/kernel/kprobes/core.c | 15 +++++++++++++-
> arch/x86/kernel/kprobes/opt.c | 38 +++++++++++++++++++++++++++++-----
> 3 files changed, 49 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h
> index 95b1f053bd96..ee669cdb5709 100644
> --- a/arch/x86/include/asm/kprobes.h
> +++ b/arch/x86/include/asm/kprobes.h
> @@ -65,6 +65,8 @@ struct arch_specific_insn {
> */
> bool boostable;
> bool if_modifier;
> + /* Number of bytes of text poked */
> + int tp_len;
> };
>
> struct arch_optimized_insn {
> diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
> index 579d30e91a36..8513594bfed1 100644
> --- a/arch/x86/kernel/kprobes/core.c
> +++ b/arch/x86/kernel/kprobes/core.c
> @@ -33,6 +33,7 @@
> #include <linux/hardirq.h>
> #include <linux/preempt.h>
> #include <linux/sched/debug.h>
> +#include <linux/perf_event.h>
> #include <linux/extable.h>
> #include <linux/kdebug.h>
> #include <linux/kallsyms.h>
> @@ -470,6 +471,9 @@ static int arch_copy_kprobe(struct kprobe *p)
> /* Also, displacement change doesn't affect the first byte */
> p->opcode = buf[0];
>
> + p->ainsn.tp_len = len;
> + perf_event_text_poke(p->ainsn.insn, NULL, 0, buf, len);
> +
> /* OK, write back the instruction(s) into ROX insn buffer */
> text_poke(p->ainsn.insn, buf, len);
>
> @@ -501,12 +505,18 @@ int arch_prepare_kprobe(struct kprobe *p)
>
> void arch_arm_kprobe(struct kprobe *p)
> {
> - text_poke(p->addr, ((unsigned char []){INT3_INSN_OPCODE}), 1);
> + u8 int3 = INT3_INSN_OPCODE;
> +
> + text_poke(p->addr, &int3, 1);
> text_poke_sync();
> + perf_event_text_poke(p->addr, &p->opcode, 1, &int3, 1);
> }
>
> void arch_disarm_kprobe(struct kprobe *p)
> {
> + u8 int3 = INT3_INSN_OPCODE;
> +
> + perf_event_text_poke(p->addr, &int3, 1, &p->opcode, 1);
> text_poke(p->addr, &p->opcode, 1);
> text_poke_sync();
> }
> @@ -514,6 +524,9 @@ void arch_disarm_kprobe(struct kprobe *p)
> void arch_remove_kprobe(struct kprobe *p)
> {
> if (p->ainsn.insn) {
> + /* Record the perf event before freeing the slot */
> + perf_event_text_poke(p->ainsn.insn, p->ainsn.insn,
> + p->ainsn.tp_len, NULL, 0);
> free_insn_slot(p->ainsn.insn, p->ainsn.boostable);
> p->ainsn.insn = NULL;
> }
> diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
> index 3f45b5c43a71..b1072c47b595 100644
> --- a/arch/x86/kernel/kprobes/opt.c
> +++ b/arch/x86/kernel/kprobes/opt.c
> @@ -6,6 +6,7 @@
> * Copyright (C) Hitachi Ltd., 2012
> */
> #include <linux/kprobes.h>
> +#include <linux/perf_event.h>
> #include <linux/ptrace.h>
> #include <linux/string.h>
> #include <linux/slab.h>
> @@ -331,8 +332,15 @@ int arch_within_optimized_kprobe(struct optimized_kprobe *op,
> static
> void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
> {
> - if (op->optinsn.insn) {
> - free_optinsn_slot(op->optinsn.insn, dirty);
> + u8 *slot = op->optinsn.insn;
> + if (slot) {
> + int len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE;
> +
> + /* Record the perf event before freeing the slot */
> + if (dirty)
> + perf_event_text_poke(slot, slot, len, NULL, 0);
> +
> + free_optinsn_slot(slot, dirty);
> op->optinsn.insn = NULL;
> op->optinsn.size = 0;
> }
> @@ -401,8 +409,15 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
> (u8 *)op->kp.addr + op->optinsn.size);
> len += JMP32_INSN_SIZE;
>
> + /*
> + * Note len = TMPL_END_IDX + op->optinsn.size + JMP32_INSN_SIZE is also
> + * used in __arch_remove_optimized_kprobe().
> + */
> +
> /* We have to use text_poke() for instruction buffer because it is RO */
> + perf_event_text_poke(slot, NULL, 0, buf, len);
> text_poke(slot, buf, len);
> +
> ret = 0;
> out:
> kfree(buf);
> @@ -454,10 +469,23 @@ void arch_optimize_kprobes(struct list_head *oplist)
> */
> void arch_unoptimize_kprobe(struct optimized_kprobe *op)
> {
> - arch_arm_kprobe(&op->kp);
> - text_poke(op->kp.addr + INT3_INSN_SIZE,
> - op->optinsn.copied_insn, DISP32_SIZE);
> + u8 new[JMP32_INSN_SIZE] = { INT3_INSN_OPCODE, };
> + u8 old[JMP32_INSN_SIZE];
> + u8 *addr = op->kp.addr;
> +
> + memcpy(old, op->kp.addr, JMP32_INSN_SIZE);
> + memcpy(new + INT3_INSN_SIZE,
> + op->optinsn.copied_insn,
> + JMP32_INSN_SIZE - INT3_INSN_SIZE);
> +
> + text_poke(addr, new, INT3_INSN_SIZE);
> text_poke_sync();
> + text_poke(addr + INT3_INSN_SIZE,
> + new + INT3_INSN_SIZE,
> + JMP32_INSN_SIZE - INT3_INSN_SIZE);
> + text_poke_sync();
> +
> + perf_event_text_poke(op->kp.addr, old, JMP32_INSN_SIZE, new, JMP32_INSN_SIZE);
> }
>
> /*
> --
> 2.17.1
>

--
Masami Hiramatsu <mhiramat@kernel.org>