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.
There are get stack pointer ( cur_sp = (unsigned long)regs->sp; ) and
restore ip (instruction_pointer_set(regs, orig_return_addr); ) in the
code, however I'm not sure if both is ok for any architecture and
perhaps should be moved to arch-dependent uprobes code otherwise.
Signed-off-by: Anton Arapov <an...@redhat.com>
---
kernel/events/uprobes.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 71 insertions(+), 2 deletions(-)
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index af424a4..a3b3a60 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -467,6 +467,16 @@ static void handler_chain(struct uprobe *uprobe, struct
pt_regs *regs)
up_read(&uprobe->register_rwsem);
}
+static void uretprobe_handler_chain(struct uprobe *uprobe, unsigned long
bp_vaddr, struct pt_regs *regs)
+{
+ struct uprobe_consumer *uc;
+
+ down_read(&uprobe->register_rwsem);
+ for (uc = uprobe->return_consumers; uc; uc = uc->next)
+ uc->handler(uc, regs);
+ up_read(&uprobe->register_rwsem);
+}
+
static void consumer_add(struct uprobe *uprobe, struct uprobe_consumer *uc)
{
down_write(&uprobe->consumer_rwsem);
@@ -608,6 +618,12 @@ static bool filter_chain(struct uprobe *uprobe)
if (ret)
break;
}
+ for (uc = uprobe->return_consumers; uc; uc = uc->next) {
+ /* TODO: ret = uc->filter(...) */
+ ret = true;
+ if (ret)
+ break;
+ }
up_read(&uprobe->consumer_rwsem);
return ret;
@@ -1334,6 +1350,48 @@ static inline void uretprobe_bypass_instances(unsigned
long cursp, struct uprobe
}
}
+static unsigned long uretprobe_run_handlers(struct pt_regs *regs)
+{
+ struct hlist_head *head;
+ struct hlist_node *r1, *r2;
+
+ struct return_instance *ri;
+ struct uprobe_task *utask;
+
+ struct xol_area *area;
+ unsigned long rp_trampoline_vaddr;
+ unsigned long orig_return_vaddr, cur_sp;
+
+ cur_sp = (unsigned long)regs->sp;
+ utask = current->utask;
+ uretprobe_bypass_instances(cur_sp, utask);
+
+ area = get_xol_area(current->mm);
+ rp_trampoline_vaddr = area->rp_trampoline_vaddr;
+ head = &utask->return_instances;
+ hlist_for_each_entry_safe(ri, r1, r2, head, hlist) {
+ if (ri->uprobe && ri->uprobe->return_consumers)
+ uretprobe_handler_chain(ri->uprobe,
ri->orig_return_vaddr, regs);
+
+ orig_return_vaddr = ri->orig_return_vaddr;
+ hlist_del(&ri->hlist);
+ kfree(ri);
+
+ if (orig_return_vaddr != rp_trampoline_vaddr)
+ /*
+ * This is the first ri (chronologically) pushed for
+ * this particular instance of the probed function.
+ */
+ return orig_return_vaddr;
+ }
+
+ printk(KERN_ERR "uretprobe: no instance with original return address!"
+ " pid/tgid=%d/%d", current->pid, current->tgid);
+ utask->doomed = true;
+
+ return 0;
+}
+
static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
{
struct uprobe_task *utask;
@@ -1567,12 +1625,23 @@ static void handle_swbp(struct pt_regs *regs)
{
struct uprobe_task *utask;
struct uprobe *uprobe;
- unsigned long bp_vaddr;
+ struct xol_area *area;
+ unsigned long bp_vaddr, orig_return_vaddr;
int uninitialized_var(is_swbp);
bp_vaddr = uprobe_get_swbp_addr(regs);
- uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
+ area = get_xol_area(current->mm);
+ if (area) {
+ if (bp_vaddr == area->rp_trampoline_vaddr) {
+ orig_return_vaddr = uretprobe_run_handlers(regs);
+ instruction_pointer_set(regs, orig_return_vaddr);
+ if (current->utask->doomed)
+ send_sig(SIGSEGV, current, 0);
+ return;
+ }
+ }
+ uprobe = find_active_uprobe(bp_vaddr, &is_swbp);
if (!uprobe) {
if (is_swbp > 0) {
/* No matching uprobe; signal SIGTRAP. */
--
1.8.0.2
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