linux-kernel - [PATCH] objtool,x86: Verify poke_int3

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Message-ID: <20200727104050.GH119549@hirez.programming.kicks-ass.net>
Date:   Mon, 27 Jul 2020 12:40:50 +0200
From:   peterz@...radead.org
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, mbenes@...e.cz
Subject: [PATCH] objtool,x86: Verify poke_int3_handler() is self contained


Abuse the SMAP rules to ensure poke_int3_handler() doesn't call out to
anything.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 tools/objtool/check.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -551,6 +551,14 @@ static const char *uaccess_safe_builtin[
 	"__memcpy_mcsafe",
 	"mcsafe_handle_tail",
 	"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
+	/*
+	 * Abuse alert!
+	 *
+	 * poke_int3_handler() is not in fact related to uaccess at all, we
+	 * abuse the uaccess rules to ensure poke_int3_handler() is self
+	 * contained and doesn't CALL out to other code.
+	 */
+	"poke_int3_handler",
 	NULL
 };