When a uprobe with return consumer is hit, prepare_uretprobe function is
invoked. It creates return_instance, hijacks return address and replaces
it with the trampoline.
N.B. it might be a good idea to introduce get_uprobe() to reflect
put_uprobe() later, but it is not a subject of this patchset.
v3:
- protected uprobe with refcounter. See atomic_inc in prepare_uretprobe()
and put_uprobe() in a following patch in handle_uretprobe()
v2:
- get rid of ->return_consumers member from struct uprobe, introduce
rp_handler() in consumer
Signed-off-by: Anton Arapov <an...@redhat.com>
---
include/linux/uprobes.h | 5 +++++
kernel/events/uprobes.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++--
2 files changed, 55 insertions(+), 2 deletions(-)
diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
index a28bdee..6aaa1ce 100644
--- a/include/linux/uprobes.h
+++ b/include/linux/uprobes.h
@@ -69,6 +69,10 @@ struct uprobe_task {
enum uprobe_task_state state;
struct arch_uprobe_task autask;
+ /*
+ * list for tracking uprobes with return consumers
+ */
+ struct hlist_head return_uprobes;
struct uprobe *active_uprobe;
unsigned long xol_vaddr;
@@ -92,6 +96,7 @@ struct xol_area {
* the vma go away, and we must handle that reasonably gracefully.
*/
unsigned long vaddr; /* Page(s) of instruction slots
*/
+ unsigned long rp_trampoline_vaddr; /* trampoline address */
};
struct uprobes_state {
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 69bf060..57f70cd 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -75,6 +75,12 @@ struct uprobe {
struct arch_uprobe arch;
};
+struct return_uprobe_i {
+ struct uprobe *uprobe;
+ struct hlist_node hlist; /* node in list */
+ unsigned long orig_ret_vaddr; /* original return address */
+};
+
/*
* valid_vma: Verify if the specified vma is an executable vma
* Relax restrictions while unregistering: vm_flags might have
@@ -1336,11 +1342,48 @@ void uprobe_copy_process(struct task_struct *t)
*/
static struct uprobe_task *get_utask(void)
{
- if (!current->utask)
+ if (!current->utask) {
current->utask = kzalloc(sizeof(struct uprobe_task),
GFP_KERNEL);
+ if (current->utask)
+ INIT_HLIST_HEAD(¤t->utask->return_uprobes);
+ }
return current->utask;
}
+static void prepare_uretprobe(struct uprobe *uprobe, struct pt_regs *regs)
+{
+ struct return_uprobe_i *ri;
+ struct uprobe_task *utask;
+ struct xol_area *area;
+ unsigned long rp_trampoline_vaddr = 0;
+ uprobe_opcode_t insn = UPROBE_SWBP_INSN;
+
+ area = get_xol_area();
+ if (area)
+ rp_trampoline_vaddr = area->rp_trampoline_vaddr;
+ if (!rp_trampoline_vaddr) {
+ rp_trampoline_vaddr = xol_get_insn_slot(&insn);
+ if (!rp_trampoline_vaddr)
+ return;
+ }
+ area->rp_trampoline_vaddr = rp_trampoline_vaddr;
+
+ ri = kzalloc(sizeof(struct return_uprobe_i), GFP_KERNEL);
+ if (!ri)
+ return;
+
+ utask = get_utask();
+ ri->orig_ret_vaddr =
arch_uretprobe_hijack_return_addr(rp_trampoline_vaddr, regs);
+ if (likely(ri->orig_ret_vaddr)) {
+ /* TODO: uretprobe bypass logic */
+ atomic_inc(&uprobe->ref);
+ ri->uprobe = uprobe;
+ INIT_HLIST_NODE(&ri->hlist);
+ hlist_add_head(&ri->hlist, &utask->return_uprobes);
+ } else
+ kfree(ri);
+}
+
/* Prepare to single-step probed instruction out of line. */
static int
pre_ssout(struct uprobe *uprobe, struct pt_regs *regs, unsigned long bp_vaddr)
@@ -1494,12 +1537,17 @@ static struct uprobe *find_active_uprobe(unsigned long
bp_vaddr, int *is_swbp)
static void handler_chain(struct uprobe *uprobe, struct pt_regs *regs)
{
+ int rc = 0;
struct uprobe_consumer *uc;
int remove = UPROBE_HANDLER_REMOVE;
down_read(&uprobe->register_rwsem);
for (uc = uprobe->consumers; uc; uc = uc->next) {
- int rc = uc->handler(uc, regs);
+ if (uc->handler)
+ rc = uc->handler(uc, regs);
+
+ if (uc->rp_handler)
+ prepare_uretprobe(uprobe, regs); /* put bp at return */
WARN(rc & ~UPROBE_HANDLER_MASK,
"bad rc=0x%x from %pf()\n", rc, uc->handler);
--
1.8.1.2
--
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