linux-kernel - [PATCH 5/7] uretprobes: return probe exit, invoke handlers

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Date:	Fri, 22 Mar 2013 14:09:02 +0100
From:	Anton Arapov <anton@...hat.com>
To:	Anton Arapov <anton@...hat.com>, Oleg Nesterov <oleg@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Josh Stone <jistone@...hat.com>,
	Frank Eigler <fche@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	adrian.m.negreanu@...el.com, Torsten.Polle@....de
Subject: [PATCH 5/7] uretprobes: return probe exit, invoke handlers

  Uretprobe handlers are invoked when the trampoline is hit, on completion the
trampoline is replaced with the saved return address and the uretprobe instance
deleted.

RFCv6 changes:
  - rework handle_uretprobe()

RFCv5 changes:
  - switch to simply linked list ->return_uprobes
  - rework handle_uretprobe()

RFCv4 changes:
  - check, whether utask is not NULL in handle_uretprobe()
  - get rid of area->rp_trampoline_vaddr
  - minor handle_uretprobe() fixups

RFCv3 changes:
  - protected uprobe with refcounter. See put_uprobe() in handle_uretprobe()
    that reflects increment in prepare_uretprobe()

RFCv2 changes:
  - get rid of ->return_consumers member from struct uprobe, introduce
    rp_handler() in consumer instead

Signed-off-by: Anton Arapov <anton@...hat.com>
---
 kernel/events/uprobes.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 59 insertions(+), 1 deletion(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 4ea3e91..91edd2c 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1623,6 +1623,56 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
 	up_read(&uprobe->register_rwsem);
 }
 
+static void handler_uretprobe_chain(struct uprobe *uprobe, struct pt_regs *regs)
+{
+	struct uprobe_consumer *uc;
+
+	down_read(&uprobe->register_rwsem);
+	for (uc = uprobe->consumers; uc; uc = uc->next) {
+		if (uc->rp_handler)
+			uc->rp_handler(uc, regs);
+	}
+	up_read(&uprobe->register_rwsem);
+}
+
+static void handle_uretprobe(struct xol_area *area, struct pt_regs *regs)
+{
+	struct uprobe_task *utask;
+	struct return_instance *ri, *tmp;
+	unsigned long prev_ret_vaddr;
+
+	utask = get_utask();
+	if (!utask)
+		return;
+
+	ri = utask->return_instances;
+	if (!ri)
+		return;
+
+	instruction_pointer_set(regs, ri->orig_ret_vaddr);
+
+	while (ri) {
+		if (ri->uprobe->consumers)
+			handler_uretprobe_chain(ri->uprobe, regs);
+
+		put_uprobe(ri->uprobe);
+		tmp = ri;
+		prev_ret_vaddr = tmp->orig_ret_vaddr;
+		ri = ri->next;
+		kfree(tmp);
+
+		if (!ri || ri->dirty == false) {
+			/*
+			 * This is the first return uprobe (chronologically)
+			 * pushed for this particular instance of the probed
+			 * function.
+			 */
+			utask->return_instances = ri;
+			return;
+		}
+	}
+}
+
 /*
  * Run handler and ask thread to singlestep.
  * Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
@@ -1631,11 +1681,19 @@ static void handle_swbp(struct pt_regs *regs)
 {
 	struct uprobe *uprobe;
 	unsigned long bp_vaddr;
+	struct xol_area *area;
 	int uninitialized_var(is_swbp);
 
 	bp_vaddr = uprobe_get_swbp_addr(regs);
-	uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
+	area = get_xol_area();
+	if (area) {
+		if (bp_vaddr == get_trampoline_vaddr(area)) {
+			handle_uretprobe(area, regs);
+			return;
+		}
+	}
 
+	uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
 	if (!uprobe) {
 		if (is_swbp > 0) {
 			/* No matching uprobe; signal SIGTRAP. */
-- 
1.8.1.4

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