gcc-12: disable '-Warray-bounds' universally for now

[ Upstream commit f0be87c42cbd341d436d06da4792e6b0c83c3aeb ]

In commit 8b202ee21839 ("s390: disable -Warray-bounds") the s390 people
disabled the '-Warray-bounds' warning for gcc-12, because the new logic
in gcc would cause warnings for their use of the S390_lowcore macro,
which accesses absolute pointers.

It turns out gcc-12 has many other issues in this area, so this takes
that s390 warning disable logic, and turns it into a kernel build config
entry instead.

Part of the intent is that we can make this all much more targeted, and
use this conflig flag to disable it in only particular configurations
that cause problems, with the s390 case as an example:

        select GCC12_NO_ARRAY_BOUNDS

and we could do that for other configuration cases that cause issues.

Or we could possibly use the CONFIG_CC_NO_ARRAY_BOUNDS thing in a more
targeted way, and disable the warning only for particular uses: again
the s390 case as an example:

  KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_CC_NO_ARRAY_BOUNDS),-Wno-array-bounds)

but this ends up just doing it globally in the top-level Makefile, since
the current issues are spread fairly widely all over:

  KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds

We'll try to limit this later, since the gcc-12 problems are rare enough
that *much* of the kernel can be built with it without disabling this
warning.

Cc: Kees Cook <keescook@chromium.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/Makefile b/Makefile
index 476cbe751b175df24795eb7ae23bc0cac2e80a46..d19e3b425bd68656015fcafb0ff008e3e3491578 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -787,6 +787,7 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG)      := -fstack-protector-strong
 KBUILD_CFLAGS += $(stackp-flags-y)
 
 KBUILD_CFLAGS-$(CONFIG_WERROR) += -Werror
+KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
 KBUILD_CFLAGS += $(KBUILD_CFLAGS-y) $(CONFIG_CC_IMPLICIT_FALLTHROUGH)
 
 ifdef CONFIG_CC_IS_CLANG

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index e084c72104f86f55dad91577800b8952366494c2..359b0cc0dc35d935a79b68ff520dbebf882b7734 100644 (file)
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -125,6 +125,7 @@ config S390
        select CLONE_BACKWARDS2
        select DMA_OPS if PCI
        select DYNAMIC_FTRACE if FUNCTION_TRACER
+       select GCC12_NO_ARRAY_BOUNDS
        select GENERIC_ALLOCATOR
        select GENERIC_CPU_AUTOPROBE
        select GENERIC_CPU_VULNERABILITIES

diff --git a/arch/s390/Makefile b/arch/s390/Makefile
index df325eacf62d261b8b0f97711120cf4ae7acc73f..eba70d585cb2c09381ffbd9ff28b0884dc00c92c 100644 (file)
--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -30,15 +30,7 @@ KBUILD_CFLAGS_DECOMPRESSOR += -fno-stack-protector
 KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning, address-of-packed-member)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO),-g)
 KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_DEBUG_INFO_DWARF4), $(call cc-option, -gdwarf-4,))
-
-ifdef CONFIG_CC_IS_GCC
-       ifeq ($(call cc-ifversion, -ge, 1200, y), y)
-               ifeq ($(call cc-ifversion, -lt, 1300, y), y)
-                       KBUILD_CFLAGS += $(call cc-disable-warning, array-bounds)
-                       KBUILD_CFLAGS_DECOMPRESSOR += $(call cc-disable-warning, array-bounds)
-               endif
-       endif
-endif
+KBUILD_CFLAGS_DECOMPRESSOR += $(if $(CONFIG_CC_NO_ARRAY_BOUNDS),-Wno-array-bounds)
 
 UTS_MACHINE    := s390x
 STACK_SIZE     := $(if $(CONFIG_KASAN),65536,16384)

diff --git a/init/Kconfig b/init/Kconfig
index b19e2eeaae80370702bbf24f789ab664d8886bcb..fa63cc019ebfce73729fa5f970dd1b01fe6b1f3a 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -899,6 +899,15 @@ config CC_IMPLICIT_FALLTHROUGH
        default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)
        default "-Wimplicit-fallthrough" if CC_IS_CLANG && $(cc-option,-Wunreachable-code-fallthrough)
 
+# Currently, disable gcc-12 array-bounds globally.
+# We may want to target only particular configurations some day.
+config GCC12_NO_ARRAY_BOUNDS
+       def_bool y
+
+config CC_NO_ARRAY_BOUNDS
+       bool
+       default y if CC_IS_GCC && GCC_VERSION >= 120000 && GCC_VERSION < 130000 && GCC12_NO_ARRAY_BOUNDS
+
 #
 # For architectures that know their GCC __int128 support is sound
 #