On Sat, 20 Mar 2021 21:16:16 +0900
Masami Hiramatsu <mhira...@kernel.org> wrote:
> On Fri, 19 Mar 2021 21:22:39 +0900
> Masami Hiramatsu <mhira...@kernel.org> wrote:
>
> > From: Josh Poimboeuf <jpoim...@redhat.com>
> >
> > Add UNWIND_HINT_FUNC on kretporbe_trampoline code so that ORC
> > information is generated on the kretprobe_trampoline correctly.
> >
>
> Test bot also found a new warning for this.
>
> > >> arch/x86/kernel/kprobes/core.o: warning: objtool:
> > >> kretprobe_trampoline()+0x25: call without frame pointer save/setup
>
> With CONFIG_FRAME_POINTER=y.
>
> Of course this can be fixed with additional "push %bp; mov %sp, %bp" before
> calling
> trampoline_handler. But actually we know that this function has a bit special
> stack frame too.
>
> Can I recover STACK_FRAME_NON_STANDARD(kretprobe_trampoline) when
> CONFIG_FRAME_POINTER=y ?
So something like this. Does it work?
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index b31058a152b6..651f337dc880 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -760,6 +760,10 @@ int kprobe_int3_handler(struct pt_regs *regs)
}
NOKPROBE_SYMBOL(kprobe_int3_handler);
+#ifdef CONFIG_FRAME_POINTER
+#undef UNWIND_HINT_FUNC
+#define UNWIND_HINT_FUNC
+#endif
/*
* When a retprobed function returns, this code saves registers and
* calls trampoline_handler() runs, which calls the kretprobe's handler.
@@ -797,7 +801,14 @@ asm(
".size kretprobe_trampoline, .-kretprobe_trampoline\n"
);
NOKPROBE_SYMBOL(kretprobe_trampoline);
-
+#ifdef CONFIG_FRAME_POINTER
+/*
+ * kretprobe_trampoline skips updating frame pointer. The frame pointer
+ * saved in trampoline_handler points to the real caller function's
+ * frame pointer.
+ */
+STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
+#endif
/*
* Called from kretprobe_trampoline
--
Masami Hiramatsu <mhira...@kernel.org>
