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* [PATCH 1/1 fyi] tools headers: Synchronize linux/bits.h with the kernel sources
@ 2025-06-12 15:38 Arnaldo Carvalho de Melo
  2025-06-13 12:24 ` Vincent Mailhol
  0 siblings, 1 reply; 5+ messages in thread
From: Arnaldo Carvalho de Melo @ 2025-06-12 15:38 UTC (permalink / raw)
  To: linux-kernel
  Cc: Adrian Hunter, Ian Rogers, James Clark, Jiri Olsa, Kan Liang,
	Lucas De Marchi, Namhyung Kim, Vincent Mailhol, Yury Norov

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 up the changes in this cset:

  5b572e8a9f3dcd6e ("bits: introduce fixed-type BIT_U*()")
  19408200c094858d ("bits: introduce fixed-type GENMASK_U*()")
  31299a5e02112411 ("bits: add comments and newlines to #if, #else and #endif directives")

This addresses these perf build warnings:

  Warning: Kernel ABI header differences:
    diff -u tools/include/linux/bits.h include/linux/bits.h

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

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Cc: Yury Norov <yury.norov@gmail.com>
Link: https://lore.kernel.org/r/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/include/linux/bits.h | 57 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 55 insertions(+), 2 deletions(-)

diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h
index 14fd0ca9a6cd1733..7ad0562191153471 100644
--- a/tools/include/linux/bits.h
+++ b/tools/include/linux/bits.h
@@ -12,6 +12,7 @@
 #define BIT_ULL_MASK(nr)	(ULL(1) << ((nr) % BITS_PER_LONG_LONG))
 #define BIT_ULL_WORD(nr)	((nr) / BITS_PER_LONG_LONG)
 #define BITS_PER_BYTE		8
+#define BITS_PER_TYPE(type)	(sizeof(type) * BITS_PER_BYTE)
 
 /*
  * Create a contiguous bitmask starting at bit position @l and ending at
@@ -19,16 +20,68 @@
  * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
  */
 #if !defined(__ASSEMBLY__)
+
+/*
+ * Missing asm support
+ *
+ * GENMASK_U*() and BIT_U*() depend on BITS_PER_TYPE() which relies on sizeof(),
+ * something not available in asm. Nevertheless, fixed width integers is a C
+ * concept. Assembly code can rely on the long and long long versions instead.
+ */
+
 #include <linux/build_bug.h>
 #include <linux/compiler.h>
+#include <linux/overflow.h>
+
 #define GENMASK_INPUT_CHECK(h, l) BUILD_BUG_ON_ZERO(const_true((l) > (h)))
-#else
+
+/*
+ * Generate a mask for the specified type @t. Additional checks are made to
+ * guarantee the value returned fits in that type, relying on
+ * -Wshift-count-overflow compiler check to detect incompatible arguments.
+ * For example, all these create build errors or warnings:
+ *
+ * - GENMASK(15, 20): wrong argument order
+ * - GENMASK(72, 15): doesn't fit unsigned long
+ * - GENMASK_U32(33, 15): doesn't fit in a u32
+ */
+#define GENMASK_TYPE(t, h, l)					\
+	((t)(GENMASK_INPUT_CHECK(h, l) +			\
+	     (type_max(t) << (l) &				\
+	      type_max(t) >> (BITS_PER_TYPE(t) - 1 - (h)))))
+
+#define GENMASK_U8(h, l)	GENMASK_TYPE(u8, h, l)
+#define GENMASK_U16(h, l)	GENMASK_TYPE(u16, h, l)
+#define GENMASK_U32(h, l)	GENMASK_TYPE(u32, h, l)
+#define GENMASK_U64(h, l)	GENMASK_TYPE(u64, h, l)
+
+/*
+ * Fixed-type variants of BIT(), with additional checks like GENMASK_TYPE(). The
+ * following examples generate compiler warnings due to -Wshift-count-overflow:
+ *
+ * - BIT_U8(8)
+ * - BIT_U32(-1)
+ * - BIT_U32(40)
+ */
+#define BIT_INPUT_CHECK(type, nr) \
+	BUILD_BUG_ON_ZERO(const_true((nr) >= BITS_PER_TYPE(type)))
+
+#define BIT_TYPE(type, nr) ((type)(BIT_INPUT_CHECK(type, nr) + BIT_ULL(nr)))
+
+#define BIT_U8(nr)	BIT_TYPE(u8, nr)
+#define BIT_U16(nr)	BIT_TYPE(u16, nr)
+#define BIT_U32(nr)	BIT_TYPE(u32, nr)
+#define BIT_U64(nr)	BIT_TYPE(u64, nr)
+
+#else /* defined(__ASSEMBLY__) */
+
 /*
  * BUILD_BUG_ON_ZERO is not available in h files included from asm files,
  * disable the input check if that is the case.
  */
 #define GENMASK_INPUT_CHECK(h, l) 0
-#endif
+
+#endif /* !defined(__ASSEMBLY__) */
 
 #define GENMASK(h, l) \
 	(GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
-- 
2.49.0


^ permalink raw reply related	[flat|nested] 5+ messages in thread
* [PATCH 1/1 fyi] tools headers: Synchronize linux/bits.h with the kernel sources
@ 2024-04-26 20:08 Arnaldo Carvalho de Melo
  0 siblings, 0 replies; 5+ messages in thread
From: Arnaldo Carvalho de Melo @ 2024-04-26 20:08 UTC (permalink / raw)
  To: linux-kernel
  Cc: Adrian Hunter, Ian Rogers, Jiri Olsa, Kan Liang, Namhyung Kim,
	Paolo Bonzini

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.

The way these headers are used in perf are not restricted to just
including them to compile something.

There are sometimes used in scripts that convert defines into string
tables, etc, so some change may break one of these scripts, or new MSRs
may use some different #define pattern, etc.

E.g.:

  $ ls -1 tools/perf/trace/beauty/*.sh | head -5
  tools/perf/trace/beauty/arch_errno_names.sh
  tools/perf/trace/beauty/drm_ioctl.sh
  tools/perf/trace/beauty/fadvise.sh
  tools/perf/trace/beauty/fsconfig.sh
  tools/perf/trace/beauty/fsmount.sh
  $
  $ tools/perf/trace/beauty/fadvise.sh
  static const char *fadvise_advices[] = {
        [0] = "NORMAL",
        [1] = "RANDOM",
        [2] = "SEQUENTIAL",
        [3] = "WILLNEED",
        [4] = "DONTNEED",
        [5] = "NOREUSE",
  };
  $

The tools/perf/check-headers.sh script, part of the tools/ build
process, points out changes in the original files.

So its important not to touch the copies in tools/ when doing changes in
the original kernel headers, that will be done later, when
check-headers.sh inform about the change to the perf tools hackers.

To pick up the changes in this cset:

   3c7a8e190bc58081 ("uapi: introduce uapi-friendly macros for GENMASK")

That just causes perf to rebuild. Its just some macros going to an uapi
header that we now have to grab a copy into tools/ as well.

This addresses this perf build warning:

  Warning: Kernel ABI header differences:
    diff -u tools/include/linux/bits.h include/linux/bits.h

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/lkml/
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/include/linux/bits.h                   |  8 +-------
 tools/include/uapi/asm-generic/bitsperlong.h |  4 ++++
 tools/include/uapi/linux/bits.h              | 15 +++++++++++++++
 tools/perf/check-headers.sh                  |  1 +
 4 files changed, 21 insertions(+), 7 deletions(-)
 create mode 100644 tools/include/uapi/linux/bits.h

diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h
index 7c0cf5031abe8796..0eb24d21aac2142c 100644
--- a/tools/include/linux/bits.h
+++ b/tools/include/linux/bits.h
@@ -4,6 +4,7 @@
 
 #include <linux/const.h>
 #include <vdso/bits.h>
+#include <uapi/linux/bits.h>
 #include <asm/bitsperlong.h>
 
 #define BIT_MASK(nr)		(UL(1) << ((nr) % BITS_PER_LONG))
@@ -30,15 +31,8 @@
 #define GENMASK_INPUT_CHECK(h, l) 0
 #endif
 
-#define __GENMASK(h, l) \
-	(((~UL(0)) - (UL(1) << (l)) + 1) & \
-	 (~UL(0) >> (BITS_PER_LONG - 1 - (h))))
 #define GENMASK(h, l) \
 	(GENMASK_INPUT_CHECK(h, l) + __GENMASK(h, l))
-
-#define __GENMASK_ULL(h, l) \
-	(((~ULL(0)) - (ULL(1) << (l)) + 1) & \
-	 (~ULL(0) >> (BITS_PER_LONG_LONG - 1 - (h))))
 #define GENMASK_ULL(h, l) \
 	(GENMASK_INPUT_CHECK(h, l) + __GENMASK_ULL(h, l))
 
diff --git a/tools/include/uapi/asm-generic/bitsperlong.h b/tools/include/uapi/asm-generic/bitsperlong.h
index 352cb81947b87697..fadb3f857f2855db 100644
--- a/tools/include/uapi/asm-generic/bitsperlong.h
+++ b/tools/include/uapi/asm-generic/bitsperlong.h
@@ -24,4 +24,8 @@
 #endif
 #endif
 
+#ifndef __BITS_PER_LONG_LONG
+#define __BITS_PER_LONG_LONG 64
+#endif
+
 #endif /* _UAPI__ASM_GENERIC_BITS_PER_LONG */
diff --git a/tools/include/uapi/linux/bits.h b/tools/include/uapi/linux/bits.h
new file mode 100644
index 0000000000000000..3c2a101986a314f6
--- /dev/null
+++ b/tools/include/uapi/linux/bits.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* bits.h: Macros for dealing with bitmasks.  */
+
+#ifndef _UAPI_LINUX_BITS_H
+#define _UAPI_LINUX_BITS_H
+
+#define __GENMASK(h, l) \
+        (((~_UL(0)) - (_UL(1) << (l)) + 1) & \
+         (~_UL(0) >> (__BITS_PER_LONG - 1 - (h))))
+
+#define __GENMASK_ULL(h, l) \
+        (((~_ULL(0)) - (_ULL(1) << (l)) + 1) & \
+         (~_ULL(0) >> (__BITS_PER_LONG_LONG - 1 - (h))))
+
+#endif /* _UAPI_LINUX_BITS_H */
diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh
index 9c84fd0490707452..672421b858ac1a7f 100755
--- a/tools/perf/check-headers.sh
+++ b/tools/perf/check-headers.sh
@@ -9,6 +9,7 @@ FILES=(
   "include/uapi/linux/const.h"
   "include/uapi/drm/drm.h"
   "include/uapi/drm/i915_drm.h"
+  "include/uapi/linux/bits.h"
   "include/uapi/linux/fadvise.h"
   "include/uapi/linux/fscrypt.h"
   "include/uapi/linux/kcmp.h"
-- 
2.44.0


^ permalink raw reply related	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2025-06-13 19:47 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2025-06-12 15:38 [PATCH 1/1 fyi] tools headers: Synchronize linux/bits.h with the kernel sources Arnaldo Carvalho de Melo
2025-06-13 12:24 ` Vincent Mailhol
2025-06-13 19:21   ` Arnaldo Carvalho de Melo
2025-06-13 19:47     ` Arnaldo Carvalho de Melo
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2024-04-26 20:08 Arnaldo Carvalho de Melo

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