Commit 3e46bb40 authored by Adrian Hunter's avatar Adrian Hunter Committed by Peter Zijlstra
Browse files

perf/x86: Add perf text poke events for kprobes 



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: default avatarAdrian Hunter <adrian.hunter@intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Link: https://lkml.kernel.org/r/20200512121922.8997-6-adrian.hunter@intel.com
parent 69e49088

arch/x86/include/asm/kprobes.h

+2 −0
Original line number Diff line number Diff line
@@ -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 {

arch/x86/kernel/kprobes/core.c

+14 −1
Original line number Diff line number Diff line
@@ -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;

	}

arch/x86/kernel/kprobes/opt.c

+33 −5
Original line number Diff line number Diff line
@@ -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>
@@ -352,8 +353,15 @@ 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;

	}
@@ -424,8 +432,15 @@ 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);
@@ -477,10 +492,23 @@ 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);

}



/*

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