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Commit 737480a0 authored by KUMANO Syuhei's avatar KUMANO Syuhei Committed by Ingo Molnar
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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
              ln-897   [000] 20404.133727: event1: (kretprobe_trampoline+0x0/0x4c <- sys_symlink)
              ln-897   [000] 20404.133747: event2: (system_call_fastpath+0x16/0x1b <- sys_symlink)

(with this patch)

 # cat trace
              ln-740   [000] 13799.491076: event1: (system_call_fastpath+0x16/0x1b <- sys_symlink)
              ln-740   [000] 13799.491096: event2: (system_call_fastpath+0x16/0x1b <- sys_symlink)

Signed-off-by: default avatarKUMANO Syuhei <kumano.prog@gmail.com>
Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
LKML-Reference: <1281853084.3254.11.camel@camp10-laptop>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f2036884

arch/x86/kernel/kprobes.c

+22 −3
Original line number Diff line number Diff line
@@ -709,6 +709,7 @@ static __used __kprobes void *trampoline_handler(struct pt_regs *regs) 
	struct hlist_node *node, *tmp;

	unsigned long flags, orig_ret_address = 0;

	unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline;

	kprobe_opcode_t *correct_ret_addr = NULL;



	INIT_HLIST_HEAD(&empty_rp);

	kretprobe_hash_lock(current, &head, &flags);
@@ -740,14 +741,34 @@ static __used __kprobes void *trampoline_handler(struct pt_regs *regs) 
			/* another task is sharing our hash bucket */

			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, node, 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) {

			__get_cpu_var(current_kprobe) = &ri->rp->kp;

			get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE;

			ri->ret_addr = correct_ret_addr;

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

			__get_cpu_var(current_kprobe) = NULL;

		}



		orig_ret_address = (unsigned long)ri->ret_addr;

		recycle_rp_inst(ri, &empty_rp);



		if (orig_ret_address != trampoline_address)
@@ -759,8 +780,6 @@ static __used __kprobes void *trampoline_handler(struct pt_regs *regs) 
			break;

	}



	kretprobe_assert(ri, orig_ret_address, trampoline_address);



	kretprobe_hash_unlock(current, &flags);



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