From: Peter Zijlstra Date: Fri, 16 Jan 2026 18:18:16 +0000 (+0100) Subject: compiler: Use __typeof_unqual__() for __unqual_scalar_typeof() X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fd69b2f7d5f4e1d89cea4cdfa6f15e7fa53d8358;p=thirdparty%2Fkernel%2Flinux.git compiler: Use __typeof_unqual__() for __unqual_scalar_typeof() The recent changes to get_unaligned() resulted in a new sparse warning: net/rds/ib_cm.c:96:35: sparse: sparse: incorrect type in argument 1 (different modifiers) @@ expected void * @@ got restricted __be64 const * @@ net/rds/ib_cm.c:96:35: sparse: expected void * net/rds/ib_cm.c:96:35: sparse: got restricted __be64 const * The updated get_unaligned_t() uses __unqual_scalar_typeof() to get an unqualified type. This works correctly for the compilers, but fails for sparse when the data type is __be64 (or any other __beNN variant). On sparse runs (C=[12]) __beNN types are annotated with __attribute__((bitwise)). That annotation allows sparse to detect incompatible operations on __beNN variables, but it also prevents sparse from evaluating the _Generic() in __unqual_scalar_typeof() and map __beNN to a unqualified scalar type, so it ends up with the default, i.e. the original qualified type of a 'const __beNN' pointer. That then ends up as the first pointer argument to builtin_memcpy(), which obviously causes the above sparse warnings. The sparse git tree supports typeof_unqual() now, which allows to use it instead of the _Generic() based __unqual_scalar_typeof(). With that sparse correctly evaluates the unqualified type and keeps the __beNN logic intact. The downside is that this requires a top of tree sparse build and an old sparse version will emit a metric ton of incomprehensible error messages before it dies with a segfault. Therefore implement a sanity check which validates that the checker is available and capable of handling typeof_unqual(). Emit a warning if not so the user can take informed action. [ tglx: Move the evaluation of USE_TYPEOF_UNQUAL to compiler_types.h so it is set before use and implement the sanity checker ] Reported-by: kernel test robot Signed-off-by: Peter Zijlstra Signed-off-by: Thomas Gleixner Acked-by: Ian Rogers Link: https://patch.msgid.link/87ecnp2zh3.ffs@tglx Closes: https://lore.kernel.org/oe-kbuild-all/202601150001.sKSN644a-lkp@intel.com/ --- diff --git a/Makefile b/Makefile index 9d38125263fb0..179c9d9a56dd6 100644 --- a/Makefile +++ b/Makefile @@ -1187,6 +1187,14 @@ CHECKFLAGS += $(if $(CONFIG_CPU_BIG_ENDIAN),-mbig-endian,-mlittle-endian) # the checker needs the correct machine size CHECKFLAGS += $(if $(CONFIG_64BIT),-m64,-m32) +# Validate the checker is available and functional +ifneq ($(KBUILD_CHECKSRC), 0) + ifneq ($(shell $(srctree)/scripts/checker-valid.sh $(CHECK) $(CHECKFLAGS)), 1) + $(warning C=$(KBUILD_CHECKSRC) specified, but $(CHECK) is not available or not up to date) + KBUILD_CHECKSRC = 0 + endif +endif + # Default kernel image to build when no specific target is given. # KBUILD_IMAGE may be overruled on the command line or # set in the environment diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 04487c9bd7510..c601222b495a2 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -230,16 +230,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val, __BUILD_BUG_ON_ZERO_MSG(!__is_noncstr(p), \ "must be non-C-string (not NUL-terminated)") -/* - * Use __typeof_unqual__() when available. - * - * XXX: Remove test for __CHECKER__ once - * sparse learns about __typeof_unqual__(). - */ -#if CC_HAS_TYPEOF_UNQUAL && !defined(__CHECKER__) -# define USE_TYPEOF_UNQUAL 1 -#endif - /* * Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof * operator when available, to return an unqualified type of the exp. diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index d3318a3c25777..377df1e640968 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -562,6 +562,14 @@ struct ftrace_likely_data { #define asm_inline asm #endif +#ifndef __ASSEMBLY__ +/* + * Use __typeof_unqual__() when available. + */ +#if CC_HAS_TYPEOF_UNQUAL || defined(__CHECKER__) +# define USE_TYPEOF_UNQUAL 1 +#endif + /* Are two types/vars the same type (ignoring qualifiers)? */ #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) @@ -569,6 +577,7 @@ struct ftrace_likely_data { * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving * non-scalar types unchanged. */ +#ifndef USE_TYPEOF_UNQUAL /* * Prefer C11 _Generic for better compile-times and simpler code. Note: 'char' * is not type-compatible with 'signed char', and we define a separate case. @@ -586,6 +595,10 @@ struct ftrace_likely_data { __scalar_type_to_expr_cases(long), \ __scalar_type_to_expr_cases(long long), \ default: (x))) +#else +#define __unqual_scalar_typeof(x) __typeof_unqual__(x) +#endif +#endif /* !__ASSEMBLY__ */ /* Is this type a native word size -- useful for atomic operations */ #define __native_word(t) \ diff --git a/scripts/checker-valid.sh b/scripts/checker-valid.sh new file mode 100755 index 0000000000000..625a789ed1c8b --- /dev/null +++ b/scripts/checker-valid.sh @@ -0,0 +1,19 @@ +#!/bin/sh -eu +# SPDX-License-Identifier: GPL-2.0 + +[ ! -x "$(command -v "$1")" ] && exit 1 + +tmp_file=$(mktemp) +trap "rm -f $tmp_file" EXIT + +cat << EOF >$tmp_file +static inline int u(const int *q) +{ + __typeof_unqual__(*q) v = *q; + return v; +} +EOF + +# sparse happily exits with 0 on error so validate +# there is none on stderr. Use awk as grep is a pain with sh -e +$@ $tmp_file 2>&1 | awk -v c=1 '/error/{c=0}END{print c}'