objtool reports the following warning for kretprobe_trampoline():
arch/x86/kernel/kprobes/core.o: warning: objtool:
kretprobe_trampoline()+0x20: call without frame pointer save/setup
kretprobes are a special case where the stack is intentionally wrong.
The return address isn't known at the beginning of the trampoline, so
the stack frame can't be set up properly before it calls
trampoline_handler().
Because kretprobe handlers don't sleep, the frame pointer doesn't *have*
to be accurate in the trampoline. So it's ok to tell objtool to ignore
it. This results in no actual changes to the generated code.
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
Cc: Ananth N Mavinakayanahalli <ana...@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamur...@intel.com>
Cc: "David S. Miller" <da...@davemloft.net>
Cc: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
---
arch/x86/kernel/kprobes/core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 48acaac..ae703ac 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -49,6 +49,7 @@
#include <linux/kdebug.h>
#include <linux/kallsyms.h>
#include <linux/ftrace.h>
+#include <linux/frame.h>
#include <asm/cacheflush.h>
#include <asm/desc.h>
@@ -703,6 +704,7 @@ asm(
".size kretprobe_trampoline, .-kretprobe_trampoline\n"
);
NOKPROBE_SYMBOL(kretprobe_trampoline);
+STACK_FRAME_NON_STANDARD(kretprobe_trampoline);
/*
* Called from kretprobe_trampoline
--
2.4.3
