[PATCH 5.4 320/320] Revert "ia64: kprobes: Use generic kretprobe trampoline handler"

Greg Kroah-Hartman
2022-01-24T20:33:05Z

From: Masami Hiramatsu <mhiramat@kernel.org>

This reverts commit 77fa5e15c933a1ec812de61ad709c00aa51e96ae.

Since the upstream commit e792ff804f49720ce003b3e4c618b5d996256a18
depends on the generic kretprobe trampoline handler, which was
introduced by commit 66ada2ccae4e ("kprobes: Add generic kretprobe
trampoline handler") but that is not ported to the stable kernel
because it is not a bugfix series.
So revert this commit to fix a build error.

NOTE: I keep commit a7fe2378454c ("ia64: kprobes: Fix to pass
correct trampoline address to the handler") on the tree, that seems
just a cleanup without the original reverted commit, but it would
be better to use dereference_function_descriptor() macro instead
of accessing descriptor's field directly.

Fixes: 77fa5e15c933 ("ia64: kprobes: Use generic kretprobe trampoline handler")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/ia64/kernel/kprobes.c | 78 +++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 75 insertions(+), 3 deletions(-)

--- a/arch/ia64/kernel/kprobes.c
+++ b/arch/ia64/kernel/kprobes.c
@@ -396,10 +396,83 @@ static void kretprobe_trampoline(void)
{
}

+/*
+ * At this point the target function has been tricked into
+ * returning into our trampoline. Lookup the associated instance
+ * and then:
+ * - call the handler function
+ * - cleanup by marking the instance as unused
+ * - long jump back to the original return address
+ */
int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
{
- regs->cr_iip = __kretprobe_trampoline_handler(regs,
- dereference_function_descriptor(kretprobe_trampoline), NULL);
+ struct kretprobe_instance *ri = NULL;
+ struct hlist_head *head, empty_rp;
+ struct hlist_node *tmp;
+ unsigned long flags, orig_ret_address = 0;
+ unsigned long trampoline_address =
+ (unsigned long)dereference_function_descriptor(kretprobe_trampoline);
+
+ INIT_HLIST_HEAD(&empty_rp);
+ kretprobe_hash_lock(current, &head, &flags);
+
+ /*
+ * It is possible to have multiple instances associated with a given
+ * task either because an multiple functions in the call path
+ * have a return probe installed on them, and/or more than one return
+ * return probe was registered for a target function.
+ *
+ * We can handle this because:
+ * - instances are always inserted at the head of the list
+ * - when multiple return probes are registered for the same
+ * function, the first instance's ret_addr will point to the
+ * real return address, and all the rest will point to
+ * kretprobe_trampoline
+ */
+ hlist_for_each_entry_safe(ri, tmp, head, hlist) {
+ if (ri->task != current)
+ /* 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;
+ }
+
+ regs->cr_iip = orig_ret_address;
+
+ hlist_for_each_entry_safe(ri, tmp, head, hlist) {
+ if (ri->task != current)
+ /* another task is sharing our hash bucket */
+ continue;
+
+ if (ri->rp && ri->rp->handler)
+ ri->rp->handler(ri, regs);
+
+ orig_ret_address = (unsigned long)ri->ret_addr;
+ recycle_rp_inst(ri, &empty_rp);
+
+ 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);
+
+ kretprobe_hash_unlock(current, &flags);
+
+ hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {
+ hlist_del(&ri->hlist);
+ kfree(ri);
+ }
/*
* By returning a non-zero value, we are telling
* kprobe_handler() that we don't want the post_handler
@@ -412,7 +485,6 @@ void __kprobes arch_prepare_kretprobe(st
struct pt_regs *regs)
{
ri->ret_addr = (kprobe_opcode_t *)regs->b0;
- ri->fp = NULL;

/* Replace the return addr with trampoline addr */
regs->b0 = (unsigned long)dereference_function_descriptor(kretprobe_trampoline);