[PATCH v2 09/10] compiler/gcc: Raise minimum GCC version for kernel builds to 4.8

Will Deacon
2020-01-23T15:34:17Z

It is very rare to see versions of GCC prior to 4.8 being used to build
the mainline kernel. These old compilers are also know to have codegen
issues which can lead to silent miscompilation:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145

Raise the minimum GCC version for kernel build to 4.8 and remove some
tautological Kconfig dependencies as a consequence.

Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>
---
Documentation/process/changes.rst | 2 +-
arch/arm/crypto/Kconfig | 12 ++++++------
crypto/Kconfig | 1 -
include/linux/compiler-gcc.h | 5 ++---
init/Kconfig | 1 -
scripts/Kconfig.include | 3 ---
scripts/gcc-plugins/Kconfig | 4 +---
7 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index 2284f2221f02..f2cbfa901cc8 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -29,7 +29,7 @@ you probably needn't concern yourself with pcmciautils.
====================== =============== ========================================
Program Minimal version Command to check the version
====================== =============== ========================================
-GNU C 4.6 gcc --version
+GNU C 4.8 gcc --version
GNU make 3.81 make --version
binutils 2.21 ld -v
flex 2.5.35 flex --version
diff --git a/arch/arm/crypto/Kconfig b/arch/arm/crypto/Kconfig
index 2674de6ada1f..c9bf2df85cb9 100644
--- a/arch/arm/crypto/Kconfig
+++ b/arch/arm/crypto/Kconfig
@@ -30,7 +30,7 @@ config CRYPTO_SHA1_ARM_NEON

config CRYPTO_SHA1_ARM_CE
tristate "SHA1 digest algorithm (ARM v8 Crypto Extensions)"
- depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+ depends on KERNEL_MODE_NEON
select CRYPTO_SHA1_ARM
select CRYPTO_HASH
help
@@ -39,7 +39,7 @@ config CRYPTO_SHA1_ARM_CE

config CRYPTO_SHA2_ARM_CE
tristate "SHA-224/256 digest algorithm (ARM v8 Crypto Extensions)"
- depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+ depends on KERNEL_MODE_NEON
select CRYPTO_SHA256_ARM
select CRYPTO_HASH
help
@@ -96,7 +96,7 @@ config CRYPTO_AES_ARM_BS

config CRYPTO_AES_ARM_CE
tristate "Accelerated AES using ARMv8 Crypto Extensions"
- depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+ depends on KERNEL_MODE_NEON
select CRYPTO_SKCIPHER
select CRYPTO_LIB_AES
select CRYPTO_SIMD
@@ -106,7 +106,7 @@ config CRYPTO_AES_ARM_CE

config CRYPTO_GHASH_ARM_CE
tristate "PMULL-accelerated GHASH using NEON/ARMv8 Crypto Extensions"
- depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+ depends on KERNEL_MODE_NEON
select CRYPTO_HASH
select CRYPTO_CRYPTD
select CRYPTO_GF128MUL
@@ -118,13 +118,13 @@ config CRYPTO_GHASH_ARM_CE

config CRYPTO_CRCT10DIF_ARM_CE
tristate "CRCT10DIF digest algorithm using PMULL instructions"
- depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+ depends on KERNEL_MODE_NEON
depends on CRC_T10DIF
select CRYPTO_HASH

config CRYPTO_CRC32_ARM_CE
tristate "CRC32(C) digest algorithm using CRC and/or PMULL instructions"
- depends on KERNEL_MODE_NEON && (CC_IS_CLANG || GCC_VERSION >= 40800)
+ depends on KERNEL_MODE_NEON
depends on CRC32
select CRYPTO_HASH

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 5575d48473bd..bd8540f56efc 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -320,7 +320,6 @@ config CRYPTO_AEGIS128
config CRYPTO_AEGIS128_SIMD
bool "Support SIMD acceleration for AEGIS-128"
depends on CRYPTO_AEGIS128 && ((ARM || ARM64) && KERNEL_MODE_NEON)
- depends on !ARM || CC_IS_CLANG || GCC_VERSION >= 40800
default y

config CRYPTO_AEGIS128_AESNI_SSE2
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index d7ee4c6bad48..e2f725273261 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -10,7 +10,8 @@
+ __GNUC_MINOR__ * 100 \
+ __GNUC_PATCHLEVEL__)

-#if GCC_VERSION < 40600
+/* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 */
+#if GCC_VERSION < 40800
# error Sorry, your compiler is too old - please upgrade it.
#endif

@@ -126,9 +127,7 @@
#if defined(CONFIG_ARCH_USE_BUILTIN_BSWAP) && !defined(__CHECKER__)
#define __HAVE_BUILTIN_BSWAP32__
#define __HAVE_BUILTIN_BSWAP64__
-#if GCC_VERSION >= 40800
#define __HAVE_BUILTIN_BSWAP16__
-#endif
#endif /* CONFIG_ARCH_USE_BUILTIN_BSWAP && !__CHECKER__ */

#if GCC_VERSION >= 70000
diff --git a/init/Kconfig b/init/Kconfig
index bdc2f1b1667b..46729aa2ca0b 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1257,7 +1257,6 @@ config LD_DEAD_CODE_DATA_ELIMINATION
bool "Dead code and data elimination (EXPERIMENTAL)"
depends on HAVE_LD_DEAD_CODE_DATA_ELIMINATION
depends on EXPERT
- depends on !(FUNCTION_TRACER && CC_IS_GCC && GCC_VERSION < 40800)
depends on $(cc-option,-ffunction-sections -fdata-sections)
depends on $(ld-option,--gc-sections)
help
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 4e645a798b56..5b7dc6635c4e 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -43,6 +43,3 @@ gcc-version := $(shell,$(srctree)/scripts/gcc-version.sh $(CC))

# Return y if the compiler is GCC, n otherwise
cc-is-gcc := $(success,$(CC) --version | head -n 1 | grep -q gcc)
-
-# Warn if the compiler is GCC prior to 4.8
-$(warning-if,$(if-success,[ $(gcc-version) -lt 40800 ],$(cc-is-gcc),n),"Your compiler is old and may miscompile the kernel due to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 - please upgrade it.")
diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index e3569543bdac..a0f669cd224f 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -1,9 +1,7 @@
# SPDX-License-Identifier: GPL-2.0-only
-preferred-plugin-hostcc := $(if-success,[ $(gcc-version) -ge 40800 ],$(HOSTCXX),$(HOSTCC))
-
config PLUGIN_HOSTCC
string
- default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(preferred-plugin-hostcc)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC
+ default "$(shell,$(srctree)/scripts/gcc-plugin.sh "$(HOSTCXX)" "$(HOSTCXX)" "$(CC)")" if CC_IS_GCC
help
Host compiler used to build GCC plugins. This can be $(HOSTCXX),
$(HOSTCC), or a null string if GCC plugin is unsupported.
--
2.25.0.341.g760bfbb309-goog