linux-kernel - Re: Remaining randconfig objtool warnings, linux-next-20200428

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Date:   Wed, 29 Apr 2020 14:18:46 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: Remaining randconfig objtool warnings, linux-next-20200428

On Tue, Apr 28, 2020 at 11:10:44AM -0500, Josh Poimboeuf wrote:
> > ==> build/x86/0x2EA4CE4F_defconfig/log <==
> > kernel/kcov.o: warning: objtool: write_comp_data()+0x1b: call to check_kcov_mode() with UACCESS enabled
> > kernel/kcov.o: warning: objtool: __sanitizer_cov_trace_pc()+0x15: call to check_kcov_mode() with UACCESS enabled

From: Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH] objtool: Add check_kcov_mode() to the uaccess safelist

check_kcov_mode() is called by write_comp_data() and
__sanitizer_cov_trace_pc(), which are already on the uaccess safe list.
Might as well add check_kcov_mode() to the party.

This fixes the following warnings:

  kernel/kcov.o: warning: objtool: __sanitizer_cov_trace_pc()+0x15: call to check_kcov_mode() with UACCESS enabled
  kernel/kcov.o: warning: objtool: write_comp_data()+0x1b: call to check_kcov_mode() with UACCESS enabled

Reported-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 tools/objtool/check.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0c732d586924..fec890547e04 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -516,6 +516,7 @@ static const char *uaccess_safe_builtin[] = {
 	"__tsan_write16",
 	/* KCOV */
 	"write_comp_data",
+	"check_kcov_mode",
 	"__sanitizer_cov_trace_pc",
 	"__sanitizer_cov_trace_const_cmp1",
 	"__sanitizer_cov_trace_const_cmp2",
-- 
2.21.1