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

Adrian Hunter
2020-03-27T08:36:57Z

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>
---

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