[RFC PATCH v4 5/6] uretprobes: invoke return probe handlers

Anton Arapov
2013-03-04T14:39:12Z

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.

v4:
- check, whether utask is not NULL in handle_uretprobe()
? do we want a printk() for this case?
- get rid of area->rp_trampoline_vaddr
- minor handle_uretprobe() fixups
v3:
- protected uprobe with refcounter. See put_uprobe() in handle_uretprobe()
that reflects increment in prepare_uretprobe()
v2:
- get rid of ->return_consumers member from struct uprobe, introduce
rp_handler() in consumer instead

Signed-off-by: Anton Arapov <anton@redhat.com>
---
arch/x86/include/asm/uprobes.h | 5 ++++
kernel/events/uprobes.c | 57 ++++++++++++++++++++++++++++++++++++++++--
2 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
index c353555..fa9d9de 100644
--- a/arch/x86/include/asm/uprobes.h
+++ b/arch/x86/include/asm/uprobes.h
@@ -56,4 +56,9 @@ extern bool arch_uprobe_xol_was_trapped(struct task_struct *tsk);
extern int arch_uprobe_exception_notify(struct notifier_block *self, unsigned long val, void *data);
extern void arch_uprobe_abort_xol(struct arch_uprobe *aup, struct pt_regs *regs);
extern unsigned long arch_uretprobe_hijack_return_addr(unsigned long rp_trampoline_vaddr, struct pt_regs *regs);
+
+static inline unsigned long arch_uretprobe_get_sp(struct pt_regs *regs)
+{
+ return (unsigned long)regs->sp;
+}
#endif /* _ASM_UPROBES_H */
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 12acc10..e86b6ea 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1574,6 +1574,55 @@ 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 hlist_head *head;
+ struct hlist_node *tmp;
+ struct return_uprobe_i *ri;
+ struct uprobe_task *utask;
+ unsigned long orig_ret_vaddr;
+
+ /* TODO: uretprobe bypass logic */
+
+ utask = get_utask();
+ if (!utask) {
+ /* TODO:RFC task is not probed, do we want printk here? */
+ return;
+ }
+ head = &utask->return_uprobes;
+ hlist_for_each_entry_safe(ri, tmp, head, hlist) {
+ if (ri->uprobe->consumers) {
+ instruction_pointer_set(regs, ri->orig_ret_vaddr);
+ handler_uretprobe_chain(ri->uprobe, regs);
+ }
+
+ orig_ret_vaddr = ri->orig_ret_vaddr;
+ put_uprobe(ri->uprobe);
+ hlist_del(&ri->hlist);
+ kfree(ri);
+
+ if (orig_ret_vaddr != area->vaddr)
+ return;
+ }
+
+ /* TODO: change the message */
+ printk(KERN_ERR "uprobe: no instance found! pid/tgid=%d/%d",
+ current->pid, current->tgid);
+ send_sig(SIGSEGV, current, 0);
+}
+
/*
* Run handler and ask thread to singlestep.
* Ensure all non-fatal signals cannot interrupt thread while it singlesteps.
@@ -1581,6 +1630,7 @@ static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
static void handle_swbp(struct pt_regs *regs)
{
struct uprobe *uprobe;
+ struct xol_area *area;
unsigned long bp_vaddr;
int uninitialized_var(is_swbp);

@@ -1589,8 +1639,11 @@ static void handle_swbp(struct pt_regs *regs)

if (!uprobe) {
if (is_swbp > 0) {
- /* No matching uprobe; signal SIGTRAP. */
- send_sig(SIGTRAP, current, 0);
+ area = get_xol_area();
+ if (area && bp_vaddr == area->vaddr)
+ handle_uretprobe(area, regs);
+ else
+ send_sig(SIGTRAP, current, 0);
} else {
/*
* Either we raced with uprobe_unregister() or we can't
--
1.8.1.2