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Message-ID: <176868515189.510.597439739057747696.tip-bot2@tip-bot2>
Date: Sat, 17 Jan 2026 21:25:51 -0000
From: "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: kernel test robot <lkp@...el.com>, Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...nel.org>, Ian Rogers <irogers@...gle.com>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: timers/vdso] compiler: Use __typeof_unqual__() for
__unqual_scalar_typeof()
The following commit has been merged into the timers/vdso branch of tip:
Commit-ID: adc00a0daf1bb08915bceee9ae73cca682e7d5bb
Gitweb: https://git.kernel.org/tip/adc00a0daf1bb08915bceee9ae73cca682e7d5bb
Author: Peter Zijlstra <peterz@...radead.org>
AuthorDate: Fri, 16 Jan 2026 19:18:16 +01:00
Committer: Thomas Gleixner <tglx@...nel.org>
CommitterDate: Sat, 17 Jan 2026 22:18:40 +01:00
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 <lkp@...el.com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...nel.org>
Acked-by: Ian Rogers <irogers@...gle.com>
Link: https://patch.msgid.link/87ecnp2zh3.ffs@tglx
Closes: https://lore.kernel.org/oe-kbuild-all/202601150001.sKSN644a-lkp@intel.com/
---
Makefile | 8 ++++++++
include/linux/compiler.h | 10 ----------
include/linux/compiler_types.h | 11 +++++++++++
scripts/checker-valid.sh | 19 +++++++++++++++++++
4 files changed, 38 insertions(+), 10 deletions(-)
create mode 100755 scripts/checker-valid.sh
diff --git a/Makefile b/Makefile
index 9d38125..179c9d9 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 04487c9..c601222 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -231,16 +231,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
"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 d3318a3..9cf4dcf 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -562,6 +562,13 @@ struct ftrace_likely_data {
#define asm_inline asm
#endif
+/*
+ * 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 +576,7 @@ 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 +594,9 @@ 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
/* 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 0000000..625a789
--- /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}'
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