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

In commit c7eea20247b1 ("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>

diff --git a/Makefile b/Makefile
index 09208ffca353eecd8c2273decf943da0394919f8..b2e93c1a80218c6227d416af5e5044117d2d5b85 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -788,6 +788,7 @@ 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 b1a88f6cc3494bb058b11e5ab1391c7d881ea48b..5126a5db41fd0d2845278d656e19a04c970ded0e 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 d73611b35164f3a3283e2a76807026b07913f15b..495c68a4df1e9d25b98ae194d3c1095d3d29c65e 100644 (file)
--- a/arch/s390/Makefile
+++ b/arch/s390/Makefile
@@ -32,15 +32,7 @@ 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 c984afc489dead0db3d4820b708d90f73b161553..c7900e8975f181857840d861e1cddd4e8201ecc4 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -885,6 +885,15 @@ 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
 #