linux-kernel - [PATCH] kcov: Unconditionally add -fno-stack-protector to compiler options

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Message-Id: <20200615184302.7591-1-elver@google.com>
Date:   Mon, 15 Jun 2020 20:43:02 +0200
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com, akpm@...ux-foundation.org
Cc:     dvyukov@...gle.com, glider@...gle.com, andreyknvl@...gle.com,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH] kcov: Unconditionally add -fno-stack-protector to compiler options

Unconditionally add -fno-stack-protector to KCOV's compiler options, as
all supported compilers support the option. This saves a compiler
invocation to determine if the option is supported.

Because Clang does not support -fno-conserve-stack, and
-fno-stack-protector was wrapped in the same cc-option, we were missing
-fno-stack-protector with Clang. Unconditionally adding this option
fixes this for Clang.

Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Signed-off-by: Marco Elver <elver@...gle.com>
---
Split out from series:
	https://lkml.kernel.org/r/20200605082839.226418-2-elver@google.com
as there is no dependency on the preceding patch (which will be dropped).
---
 kernel/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/Makefile b/kernel/Makefile
index f3218bc5ec69..592cb549dcb8 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -35,7 +35,7 @@ KCOV_INSTRUMENT_stacktrace.o := n
 KCOV_INSTRUMENT_kcov.o := n
 KASAN_SANITIZE_kcov.o := n
 KCSAN_SANITIZE_kcov.o := n
-CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
+CFLAGS_kcov.o := $(call cc-option, -fno-conserve-stack) -fno-stack-protector
 
 # cond_syscall is currently not LTO compatible
 CFLAGS_sys_ni.o = $(DISABLE_LTO)
-- 
2.27.0.290.gba653c62da-goog