Messages in this thread Patch in this message | | | From | Masami Hiramatsu <> | Subject | [PATCH -tip v8 09/13] kprobes: Enable stacktrace from pt_regs in kretprobe handler | Date | Fri, 18 Jun 2021 16:06:46 +0900 |
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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 Nakryik <andrii@kernel.org> --- 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 | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 650cbe738666..ba729ed05cb3 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1896,6 +1896,9 @@ unsigned long __kretprobe_trampoline_handler(struct pt_regs *regs, BUG_ON(1); } + /* Set the instruction pointer to the correct address */ + instruction_pointer_set(regs, (unsigned long)correct_ret_addr); + /* Run them. */ first = current->kretprobe_instances.first; while (first) {
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