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Commit 06553175 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Jon Medhurst
Browse files

arm: kprobes: Fix the return address of multiple kretprobes 



This is arm port of commit 737480a0 ("kprobes/x86:
Fix the return address of multiple kretprobes").

Fix the return address of subsequent kretprobes when multiple
kretprobes are set on the same function.

For example:

  # cd /sys/kernel/debug/tracing
  # echo "r:event1 sys_symlink" > kprobe_events
  # echo "r:event2 sys_symlink" >> kprobe_events
  # echo 1 > events/kprobes/enable
  # ln -s /tmp/foo /tmp/bar

 (without this patch)

  # cat trace | grep -v ^#
              ln-82    [000] dn.2    68.446525: event1: (kretprobe_trampoline+0x0/0x18 <- SyS_symlink)
              ln-82    [000] dn.2    68.447831: event2: (ret_fast_syscall+0x0/0x1c <- SyS_symlink)

 (with this patch)

  # cat trace | grep -v ^#
              ln-81    [000] dn.1    39.463469: event1: (ret_fast_syscall+0x0/0x1c <- SyS_symlink)
              ln-81    [000] dn.1    39.464701: event2: (ret_fast_syscall+0x0/0x1c <- SyS_symlink)

Signed-off-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Cc: KUMANO Syuhei <kumano.prog@gmail.com>
Signed-off-by: default avatarJon Medhurst <tixy@linaro.org>
parent 91fc862c

arch/arm/probes/kprobes/core.c

+22 −2
Original line number Original line Diff line number Diff line
@@ -441,6 +441,7 @@ static __used __kprobes void *trampoline_handler(struct pt_regs *regs) 
	struct hlist_node *tmp;

	struct hlist_node *tmp;

	unsigned long flags, orig_ret_address = 0;

	unsigned long flags, orig_ret_address = 0;

	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;

	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;

	kprobe_opcode_t *correct_ret_addr = NULL;





	INIT_HLIST_HEAD(&empty_rp);

	INIT_HLIST_HEAD(&empty_rp);

	kretprobe_hash_lock(current, &head, &flags);

	kretprobe_hash_lock(current, &head, &flags);
@@ -463,14 +464,34 @@ static __used __kprobes void *trampoline_handler(struct pt_regs *regs) 
			/* another task is sharing our hash bucket */

			/* another task is sharing our hash bucket */

			continue;

			continue;





		orig_ret_address = (unsigned long)ri->ret_addr;



		if (orig_ret_address != trampoline_address)

			/*

			 * This is the real return address. Any other

			 * instances associated with this task are for

			 * other calls deeper on the call stack

			 */

			break;

	}



	kretprobe_assert(ri, orig_ret_address, trampoline_address);



	correct_ret_addr = ri->ret_addr;

	hlist_for_each_entry_safe(ri, tmp, head, hlist) {

		if (ri->task != current)

			/* another task is sharing our hash bucket */

			continue;



		orig_ret_address = (unsigned long)ri->ret_addr;

		if (ri->rp && ri->rp->handler) {

		if (ri->rp && ri->rp->handler) {

			__this_cpu_write(current_kprobe, &ri->rp->kp);

			__this_cpu_write(current_kprobe, &ri->rp->kp);

			get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;

			get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;

			ri->ret_addr = correct_ret_addr;

			ri->rp->handler(ri, regs);

			ri->rp->handler(ri, regs);

			__this_cpu_write(current_kprobe, NULL);

			__this_cpu_write(current_kprobe, NULL);

		}

		}





		orig_ret_address = (unsigned long)ri->ret_addr;

		recycle_rp_inst(ri, &empty_rp);

		recycle_rp_inst(ri, &empty_rp);





		if (orig_ret_address != trampoline_address)

		if (orig_ret_address != trampoline_address)
@@ -482,7 +503,6 @@ static __used __kprobes void *trampoline_handler(struct pt_regs *regs) 
			break;

			break;

	}

	}





	kretprobe_assert(ri, orig_ret_address, trampoline_address);

	kretprobe_hash_unlock(current, &flags);

	kretprobe_hash_unlock(current, &flags);





	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {

	hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {