From: Kees Cook <keescook@chromium.org>
Date: Wed, 13 Jul 2022 21:38:19 +0000 (-0700)
Subject: x86/alternative: Report missing return thunk details
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=49338b651f5a6ba0863296678735f0d7bb75c1ed;p=linux.git

x86/alternative: Report missing return thunk details

commit 65cdf0d623bedf0e069bb64ed52e8bb20105e2ba upstream.

Debugging missing return thunks is easier if we can see where they're
happening.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/Ys66hwtFcGbYmoiZ@hirez.programming.kicks-ass.net/
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index 8ed9ccf53b623..98a8b59f87f36 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -554,7 +554,9 @@ void __init_or_module noinline apply_returns(s32 *start, s32 *end)
 			dest = addr + insn.length + insn.immediate.value;
 
 		if (__static_call_fixup(addr, op, dest) ||
-		    WARN_ON_ONCE(dest != &__x86_return_thunk))
+		    WARN_ONCE(dest != &__x86_return_thunk,
+			      "missing return thunk: %pS-%pS: %*ph",
+			      addr, dest, 5, addr))
 			continue;
 
 		DPRINTK("return thunk at: %pS (%px) len: %d to: %pS",