From 9e6ffb996207e307ad7707d90c8e68d7b8587e21 Mon Sep 17 00:00:00 2001 From: Jan Hendrik Farr Date: Thu, 17 Oct 2024 04:39:40 +0200 Subject: [PATCH] Compiler Attributes: disable __counted_by for clang < 19.1.3 This patch disables __counted_by for clang versions < 19.1.3 because of the two issues listed below. It does this by introducing CONFIG_CC_HAS_COUNTED_BY. 1. clang < 19.1.2 has a bug that can lead to __bdos returning 0: https://github.com/llvm/llvm-project/pull/110497 2. clang < 19.1.3 has a bug that can lead to __bdos being off by 4: https://github.com/llvm/llvm-project/pull/112636 Fixes: c8248faf3ca2 ("Compiler Attributes: counted_by: Adjust name and identifier expansion") Cc: stable@vger.kernel.org # 6.6.x: 16c31dd7fdf6: Compiler Attributes: counted_by: bump min gcc version Cc: stable@vger.kernel.org # 6.6.x: 2993eb7a8d34: Compiler Attributes: counted_by: fixup clang URL Cc: stable@vger.kernel.org # 6.6.x: 231dc3f0c936: lkdtm/bugs: Improve warning message for compilers without counted_by support Cc: stable@vger.kernel.org # 6.6.x Reported-by: Nathan Chancellor Closes: https://lore.kernel.org/all/20240913164630.GA4091534@thelio-3990X/ Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202409260949.a1254989-oliver.sang@intel.com Link: https://lore.kernel.org/all/Zw8iawAF5W2uzGuh@archlinux/T/#m204c09f63c076586a02d194b87dffc7e81b8de7b Signed-off-by: Jan Hendrik Farr --- drivers/misc/lkdtm/bugs.c | 2 +- include/linux/compiler_attributes.h | 13 ------------- include/linux/compiler_types.h | 19 +++++++++++++++++++ init/Kconfig | 8 ++++++++ lib/overflow_kunit.c | 2 +- 5 files changed, 29 insertions(+), 15 deletions(-) diff --git a/drivers/misc/lkdtm/bugs.c b/drivers/misc/lkdtm/bugs.c index 62ba0152547975..376047beea3d64 100644 --- a/drivers/misc/lkdtm/bugs.c +++ b/drivers/misc/lkdtm/bugs.c @@ -445,7 +445,7 @@ static void lkdtm_FAM_BOUNDS(void) pr_err("FAIL: survived access of invalid flexible array member index!\n"); - if (!__has_attribute(__counted_by__)) + if (!IS_ENABLED(CONFIG_CC_HAS_COUNTED_BY)) pr_warn("This is expected since this %s was built with a compiler that does not support __counted_by\n", lkdtm_kernel_info); else if (IS_ENABLED(CONFIG_UBSAN_BOUNDS)) diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h index 32284cd26d52a7..c16d4199bf9231 100644 --- a/include/linux/compiler_attributes.h +++ b/include/linux/compiler_attributes.h @@ -94,19 +94,6 @@ # define __copy(symbol) #endif -/* - * Optional: only supported since gcc >= 15 - * Optional: only supported since clang >= 18 - * - * gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896 - * clang: https://github.com/llvm/llvm-project/pull/76348 - */ -#if __has_attribute(__counted_by__) -# define __counted_by(member) __attribute__((__counted_by__(member))) -#else -# define __counted_by(member) -#endif - /* * Optional: not supported by gcc * Optional: only supported since clang >= 14.0 diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 1a957ea2f4fe78..639be0f30b455d 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -323,6 +323,25 @@ struct ftrace_likely_data { #define __no_sanitize_or_inline __always_inline #endif +/* + * Optional: only supported since gcc >= 15 + * Optional: only supported since clang >= 18 + * + * gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896 + * clang: https://github.com/llvm/llvm-project/pull/76348 + * + * __bdos on clang < 19.1.2 can erroneously return 0: + * https://github.com/llvm/llvm-project/pull/110497 + * + * __bdos on clang < 19.1.3 can be off by 4: + * https://github.com/llvm/llvm-project/pull/112636 + */ +#ifdef CONFIG_CC_HAS_COUNTED_BY +# define __counted_by(member) __attribute__((__counted_by__(member))) +#else +# define __counted_by(member) +#endif + /* * Apply __counted_by() when the Endianness matches to increase test coverage. */ diff --git a/init/Kconfig b/init/Kconfig index c521e1421ad4ab..3e5c7b54a8ce70 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -120,6 +120,14 @@ config CC_HAS_ASM_INLINE config CC_HAS_NO_PROFILE_FN_ATTR def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror) +# clang needs to be at least 19.1.3 to avoid __bdos miscalculations +# https://github.com/llvm/llvm-project/pull/110497 +# https://github.com/llvm/llvm-project/pull/112636 +# TODO: when gcc 15 is released remove the build test and add gcc version check +config CC_HAS_COUNTED_BY + def_bool $(success,echo 'struct flex { int count; int array[] __attribute__((__counted_by__(count))); };' | $(CC) $(CLANG_FLAGS) -x c - -c -o /dev/null -Werror) + depends on !(CC_IS_CLANG && CLANG_VERSION < 190103) + config PAHOLE_VERSION int default $(shell,$(srctree)/scripts/pahole-version.sh $(PAHOLE)) diff --git a/lib/overflow_kunit.c b/lib/overflow_kunit.c index 2abc78367dd110..5222c6393f1168 100644 --- a/lib/overflow_kunit.c +++ b/lib/overflow_kunit.c @@ -1187,7 +1187,7 @@ static void DEFINE_FLEX_test(struct kunit *test) { /* Using _RAW_ on a __counted_by struct will initialize "counter" to zero */ DEFINE_RAW_FLEX(struct foo, two_but_zero, array, 2); -#if __has_attribute(__counted_by__) +#ifdef CONFIG_CC_HAS_COUNTED_BY int expected_raw_size = sizeof(struct foo); #else int expected_raw_size = sizeof(struct foo) + 2 * sizeof(s16);