Messages in this thread Patch in this message | | | From | Masami Hiramatsu <> | Subject | [PATCH -tip v10 12/16] kprobes: Enable stacktrace from pt_regs in kretprobe handler | Date | Thu, 29 Jul 2021 23:07:48 +0900 |
| |
Since the ORC unwinder from pt_regs requires setting up regs->ip correctly, set the correct return address to the regs->ip before calling user kretprobe handler.
This allows the kretrprobe handler to trace stack from the kretprobe's pt_regs by stack_trace_save_regs() (eBPF will do this), instead of stack tracing from the handler context by stack_trace_save() (ftrace will do this).
Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org> Tested-by: Andrii Nakryiko <andrii@kernel.org> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> --- Changes in v9: - Update comment to explain specifically why this is necessary. Changes in v8: - Update comment to clarify why this is needed. Changes in v3: - Cast the correct_ret_addr to unsigned long. --- kernel/kprobes.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 833f07f33115..ebc587b9a346 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1937,6 +1937,13 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, BUG_ON(1); } + /* + * Set the return address as the instruction pointer, because if the + * user handler calls stack_trace_save_regs() with this 'regs', + * the stack trace will start from the instruction pointer. + */ + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); + /* Run the user handler of the nodes. */ first = current->kretprobe_instances.first; while (first) {
| |