linux-kernel - [PATCH -tip v3 2/2] kcov: Unconditionally add -fno-stack-protector to compiler options

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Message-Id: <20200605082839.226418-2-elver@google.com>
Date:   Fri,  5 Jun 2020 10:28:39 +0200
From:   Marco Elver <elver@...gle.com>
To:     elver@...gle.com
Cc:     peterz@...radead.org, bp@...en8.de, tglx@...utronix.de,
        mingo@...nel.org, clang-built-linux@...glegroups.com,
        paulmck@...nel.org, dvyukov@...gle.com, glider@...gle.com,
        andreyknvl@...gle.com, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        akpm@...ux-foundation.org,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: [PATCH -tip v3 2/2] 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>
Signed-off-by: Marco Elver <elver@...gle.com>
---
v3:
* Do not wrap -fno-stack-protector in cc-option, since all KCOV-supported
  compilers support the option as pointed out by Nick.
---
 kernel/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/Makefile b/kernel/Makefile
index ce8716a04d0e..71971eb39ee7 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)
-- 
2.27.0.278.ge193c7cf3a9-goog