linux-kernel - [PATCH] kbuild: mkcompile_h: Include $LD version in /proc/version

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Message-ID: <202004020117.6E434C035@keescook>
Date:   Thu, 2 Apr 2020 01:18:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        linux-kernel@...r.kernel.org
Subject: [PATCH] kbuild: mkcompile_h: Include $LD version in /proc/version

When doing Clang builds of the kernel, it is possible to link with
either ld.bfd (binutils) or ld.lld (LLVM), but it is not possible to
discover this from a running kernel. Add the "$LD -v" output to
/proc/version.

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 init/Makefile       | 2 +-
 scripts/mkcompile_h | 8 ++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/init/Makefile b/init/Makefile
index 6246a06364d0..82c15bdb42d7 100644
--- a/init/Makefile
+++ b/init/Makefile
@@ -35,4 +35,4 @@ include/generated/compile.h: FORCE
 	@$($(quiet)chk_compile.h)
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/mkcompile_h $@	\
 	"$(UTS_MACHINE)" "$(CONFIG_SMP)" "$(CONFIG_PREEMPT)"	\
-	"$(CONFIG_PREEMPT_RT)" "$(CC) $(KBUILD_CFLAGS)"
+	"$(CONFIG_PREEMPT_RT)" "$(LD)" "$(CC) $(KBUILD_CFLAGS)"
diff --git a/scripts/mkcompile_h b/scripts/mkcompile_h
index 3a5a4b210c86..f98c07709370 100755
--- a/scripts/mkcompile_h
+++ b/scripts/mkcompile_h
@@ -6,7 +6,8 @@ ARCH=$2
 SMP=$3
 PREEMPT=$4
 PREEMPT_RT=$5
-CC=$6
+LD=$6
+CC=$7
 
 vecho() { [ "${quiet}" = "silent_" ] || echo "$@" ; }
 
@@ -72,7 +73,10 @@ UTS_VERSION="$(echo $UTS_VERSION $CONFIG_FLAGS $TIMESTAMP | cut -b -$UTS_LEN)"
   printf '#define LINUX_COMPILE_BY "%s"\n' "$LINUX_COMPILE_BY"
   echo \#define LINUX_COMPILE_HOST \"$LINUX_COMPILE_HOST\"
 
-  echo \#define LINUX_COMPILER \"`$CC -v 2>&1 | grep ' version ' | sed 's/[[:space:]]*$//'`\"
+  CC_VERSION=$($CC -v 2>&1 | grep ' version ' | sed 's/[[:space:]]*$//')
+  LD_VERSION=$($LD -v | head -n1 | sed 's/(compatible with [^)]*)//' \
+		      | sed 's/[[:space:]]*$//')
+  printf '#define LINUX_COMPILER "%s"\n' "$CC_VERSION, $LD_VERSION"
 } > .tmpcompile
 
 # Only replace the real compile.h if the new one is different,
-- 
2.20.1


-- 
Kees Cook