linux-kernel - [PATCH 1/1] tools headers asm: Sync fls headers header with the kernel sources

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Message-ID: <aQjeLkiMCefq02my@x1>
Date: Mon, 3 Nov 2025 13:54:06 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Kees Cook <kees@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
	Ian Rogers <irogers@...gle.com>,
	James Clark <james.clark@...aro.org>, Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>
Subject: [PATCH 1/1] tools headers asm: Sync fls headers header with the
 kernel sources

tldr; Just FYI, I'm carrying this on the perf tools tree.

Full explanation:

There used to be no copies, with tools/ code using kernel headers
directly. From time to time tools/perf/ broke due to legitimate kernel
hacking. At some point Linus complained about such direct usage. Then we
adopted the current model.

See further details at:

 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/include/uapi/README

To pick the changes in:

  6606c8c7e8188656 ("bitops: Add __attribute_const__ to generic ffs()-family implementations")

This addresses these tools build warnings:

  Warning: Kernel ABI header differences:
    diff -u tools/include/asm-generic/bitops/__fls.h include/asm-generic/bitops/__fls.h
    diff -u tools/include/asm-generic/bitops/fls.h include/asm-generic/bitops/fls.h
    diff -u tools/include/asm-generic/bitops/fls64.h include/asm-generic/bitops/fls64.h

Please see tools/include/uapi/README for further details.

Cc: Kees Cook <kees@...nel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/include/asm-generic/bitops/__fls.h | 2 +-
 tools/include/asm-generic/bitops/fls.h   | 2 +-
 tools/include/asm-generic/bitops/fls64.h | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/include/asm-generic/bitops/__fls.h b/tools/include/asm-generic/bitops/__fls.h
index e974ec932ec189f9..35f33780ca6c3727 100644
--- a/tools/include/asm-generic/bitops/__fls.h
+++ b/tools/include/asm-generic/bitops/__fls.h
@@ -10,7 +10,7 @@
  *
  * Undefined if no set bit exists, so code should check against 0 first.
  */
-static __always_inline unsigned int generic___fls(unsigned long word)
+static __always_inline __attribute_const__ unsigned int generic___fls(unsigned long word)
 {
 	unsigned int num = BITS_PER_LONG - 1;
 
diff --git a/tools/include/asm-generic/bitops/fls.h b/tools/include/asm-generic/bitops/fls.h
index 26f3ce1dd6e44872..8eed3437edb95c1c 100644
--- a/tools/include/asm-generic/bitops/fls.h
+++ b/tools/include/asm-generic/bitops/fls.h
@@ -10,7 +10,7 @@
  * Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
  */
 
-static __always_inline int generic_fls(unsigned int x)
+static __always_inline __attribute_const__ int generic_fls(unsigned int x)
 {
 	int r = 32;
 
diff --git a/tools/include/asm-generic/bitops/fls64.h b/tools/include/asm-generic/bitops/fls64.h
index 866f2b2304ff639f..b5f58dd261a3707d 100644
--- a/tools/include/asm-generic/bitops/fls64.h
+++ b/tools/include/asm-generic/bitops/fls64.h
@@ -16,7 +16,7 @@
  * at position 64.
  */
 #if BITS_PER_LONG == 32
-static __always_inline int fls64(__u64 x)
+static __always_inline __attribute_const__ int fls64(__u64 x)
 {
 	__u32 h = x >> 32;
 	if (h)
@@ -24,7 +24,7 @@ static __always_inline int fls64(__u64 x)
 	return fls(x);
 }
 #elif BITS_PER_LONG == 64
-static __always_inline int fls64(__u64 x)
+static __always_inline __attribute_const__ int fls64(__u64 x)
 {
 	if (x == 0)
 		return 0;
-- 
2.51.1