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Subject[PATCH V6 05/15] perf/x86: Add perf text poke events for kprobes
Date
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()

- the INT3 that activates the kprobe
i.e. arch_arm_kprobe() and arch_disarm_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()

Resulting in 8 possible text_poke events:

0: NULL -> probe.ainsn.insn (if ainsn.boostable && !kp.post_handler)
arch_copy_kprobe()

1: old0 -> INT3 arch_arm_kprobe()

// boosted kprobe active

2: NULL -> optprobe_trampoline arch_prepare_optimized_kprobe()

3: INT3,old1,old2,old3,old4 -> JMP32 arch_optimize_kprobes()

// optprobe active

4: JMP32 -> INT3,old1,old2,old3,old4

// optprobe disabled and kprobe active (this sometimes goes back to 3)
arch_unoptimize_kprobe()

5: optprobe_trampoline -> NULL arch_remove_optimized_kprobe()

// boosted kprobe active

6: INT3 -> old0 arch_disarm_kprobe()

7: probe.ainsn.insn -> NULL (if ainsn.boostable && !kp.post_handler)
arch_remove_kprobe()

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
---
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 073eb7ad2f56..143bc9abe99c 100644
--- a/arch/x86/include/asm/kprobes.h
+++ b/arch/x86/include/asm/kprobes.h
@@ -66,6 +66,8 @@ 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 4d7022a740ab..6d8b58c84cbc 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>
@@ -471,6 +472,9 @@ 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);

@@ -502,12 +506,18 @@ 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();
}
@@ -515,6 +525,9 @@ 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 ea13f6888284..f86be31d37cc 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>
@@ -354,8 +355,15 @@ 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;
}
@@ -426,8 +434,15 @@ 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);
@@ -479,10 +494,23 @@ 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
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