From df91c5bccb0c2cb868b54bd68a6ddf1fcbede6b1 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Tue, 14 Sep 2021 23:42:12 +0900 Subject: [PATCH] kprobes: Enable stacktrace from pt_regs in kretprobe handler 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). Link: https://lkml.kernel.org/r/163163053237.489837.4272653874525136832.stgit@devnote2 Suggested-by: Josh Poimboeuf Signed-off-by: Masami Hiramatsu Tested-by: Andrii Nakryiko Acked-by: Josh Poimboeuf Signed-off-by: Steven Rostedt (VMware) --- 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) { -- 2.49.0