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Subject: Re: [PATCH 15/15] tools headers: Synchronize linux/bits.h with the
 kernel sources
To:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>
Cc:     Jiri Olsa <jolsa@kernel.org>, Namhyung Kim <namhyung@kernel.org>,
        Clark Williams <williams@redhat.com>,
        linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Rikard Falkeborn <rikard.falkeborn@gmail.com>
References: <20200414164854.26026-1-acme@kernel.org>
 <20200414164854.26026-16-acme@kernel.org>
From:   Vincenzo Frascino <vincenzo.frascino@arm.com>
Message-ID: <7951882d-d13a-7b1e-36f4-73c188015161@arm.com>
Date:   Wed, 15 Apr 2020 10:14:06 +0100
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On 4/14/20 5:48 PM, Arnaldo Carvalho de Melo wrote:
> From: Arnaldo Carvalho de Melo <acme@redhat.com>
> 
> To pick up the changes in these csets:
> 
>   295bcca84916 ("linux/bits.h: add compile time sanity check of GENMASK inputs")
>   3945ff37d2f4 ("linux/bits.h: Extract common header for vDSO")
> 
> To address this tools/perf build warning:
> 
>   Warning: Kernel ABI header at 'tools/include/linux/bits.h' differs from latest version at 'include/linux/bits.h'
>   diff -u tools/include/linux/bits.h include/linux/bits.h
> 
> This clashes with usage of userspace's static_assert(), that, at least
> on glibc, is guarded by a ifnded/endif pair, do the same to our copy of
> build_bug.h and avoid that diff in check_headers.sh so that we continue
> checking for drifts with the kernel sources master copy.
> 
> This will all be tested with the set of build containers that includes
> uCLibc, musl libc, lots of glibc versions in lots of distros and cross
> build environments.
> 
> The tools/objtool, tools/bpf, etc were tested as well.
>

Acked-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # vDSO parts

> Cc: Adrian Hunter <adrian.hunter@intel.com>
> Cc: Jiri Olsa <jolsa@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: Rikard Falkeborn <rikard.falkeborn@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> ---
>  tools/include/linux/bits.h      | 24 ++++++++--
>  tools/include/linux/build_bug.h | 82 +++++++++++++++++++++++++++++++++
>  tools/include/linux/kernel.h    |  4 +-
>  tools/include/vdso/bits.h       |  9 ++++
>  tools/perf/check-headers.sh     |  2 +
>  5 files changed, 115 insertions(+), 6 deletions(-)
>  create mode 100644 tools/include/linux/build_bug.h
>  create mode 100644 tools/include/vdso/bits.h
> 
> diff --git a/tools/include/linux/bits.h b/tools/include/linux/bits.h
> index 669d69441a62..4671fbf28842 100644
> --- a/tools/include/linux/bits.h
> +++ b/tools/include/linux/bits.h
> @@ -3,9 +3,9 @@
>  #define __LINUX_BITS_H
>  
>  #include <linux/const.h>
> +#include <vdso/bits.h>
>  #include <asm/bitsperlong.h>
>  
> -#define BIT(nr)			(UL(1) << (nr))
>  #define BIT_ULL(nr)		(ULL(1) << (nr))
>  #define BIT_MASK(nr)		(UL(1) << ((nr) % BITS_PER_LONG))
>  #define BIT_WORD(nr)		((nr) / BITS_PER_LONG)
> @@ -18,12 +18,30 @@
>   * position @h. For example
>   * GENMASK_ULL(39, 21) gives us the 64bit vector 0x000000ffffe00000.
>   */
> -#define GENMASK(h, l) \
> +#if !defined(__ASSEMBLY__) && \
> +	(!defined(CONFIG_CC_IS_GCC) || CONFIG_GCC_VERSION >= 49000)
> +#include <linux/build_bug.h>
> +#define GENMASK_INPUT_CHECK(h, l) \
> +	(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
> +		__builtin_constant_p((l) > (h)), (l) > (h), 0)))
> +#else
> +/*
> + * 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
> +
> +#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) \
> +#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))
>  
>  #endif	/* __LINUX_BITS_H */
> diff --git a/tools/include/linux/build_bug.h b/tools/include/linux/build_bug.h
> new file mode 100644
> index 000000000000..cc7070c7439b
> --- /dev/null
> +++ b/tools/include/linux/build_bug.h
> @@ -0,0 +1,82 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _LINUX_BUILD_BUG_H
> +#define _LINUX_BUILD_BUG_H
> +
> +#include <linux/compiler.h>
> +
> +#ifdef __CHECKER__
> +#define BUILD_BUG_ON_ZERO(e) (0)
> +#else /* __CHECKER__ */
> +/*
> + * Force a compilation error if condition is true, but also produce a
> + * result (of value 0 and type int), so the expression can be used
> + * e.g. in a structure initializer (or where-ever else comma expressions
> + * aren't permitted).
> + */
> +#define BUILD_BUG_ON_ZERO(e) ((int)(sizeof(struct { int:(-!!(e)); })))
> +#endif /* __CHECKER__ */
> +
> +/* Force a compilation error if a constant expression is not a power of 2 */
> +#define __BUILD_BUG_ON_NOT_POWER_OF_2(n)	\
> +	BUILD_BUG_ON(((n) & ((n) - 1)) != 0)
> +#define BUILD_BUG_ON_NOT_POWER_OF_2(n)			\
> +	BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
> +
> +/*
> + * BUILD_BUG_ON_INVALID() permits the compiler to check the validity of the
> + * expression but avoids the generation of any code, even if that expression
> + * has side-effects.
> + */
> +#define BUILD_BUG_ON_INVALID(e) ((void)(sizeof((__force long)(e))))
> +
> +/**
> + * BUILD_BUG_ON_MSG - break compile if a condition is true & emit supplied
> + *		      error message.
> + * @condition: the condition which the compiler should know is false.
> + *
> + * See BUILD_BUG_ON for description.
> + */
> +#define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> +
> +/**
> + * BUILD_BUG_ON - break compile if a condition is true.
> + * @condition: the condition which the compiler should know is false.
> + *
> + * If you have some code which relies on certain constants being equal, or
> + * some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
> + * detect if someone changes it.
> + */
> +#define BUILD_BUG_ON(condition) \
> +	BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
> +
> +/**
> + * BUILD_BUG - break compile if used.
> + *
> + * If you have some code that you expect the compiler to eliminate at
> + * build time, you should use BUILD_BUG to detect if it is
> + * unexpectedly used.
> + */
> +#define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
> +
> +/**
> + * static_assert - check integer constant expression at build time
> + *
> + * static_assert() is a wrapper for the C11 _Static_assert, with a
> + * little macro magic to make the message optional (defaulting to the
> + * stringification of the tested expression).
> + *
> + * Contrary to BUILD_BUG_ON(), static_assert() can be used at global
> + * scope, but requires the expression to be an integer constant
> + * expression (i.e., it is not enough that __builtin_constant_p() is
> + * true for expr).
> + *
> + * Also note that BUILD_BUG_ON() fails the build if the condition is
> + * true, while static_assert() fails the build if the expression is
> + * false.
> + */
> +#ifndef static_assert
> +#define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
> +#define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
> +#endif // static_assert
> +
> +#endif	/* _LINUX_BUILD_BUG_H */
> diff --git a/tools/include/linux/kernel.h b/tools/include/linux/kernel.h
> index cba226948a0c..a7e54a08fb54 100644
> --- a/tools/include/linux/kernel.h
> +++ b/tools/include/linux/kernel.h
> @@ -5,6 +5,7 @@
>  #include <stdarg.h>
>  #include <stddef.h>
>  #include <assert.h>
> +#include <linux/build_bug.h>
>  #include <linux/compiler.h>
>  #include <endian.h>
>  #include <byteswap.h>
> @@ -35,9 +36,6 @@
>  	(type *)((char *)__mptr - offsetof(type, member)); })
>  #endif
>  
> -#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
> -#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
> -
>  #ifndef max
>  #define max(x, y) ({				\
>  	typeof(x) _max1 = (x);			\
> diff --git a/tools/include/vdso/bits.h b/tools/include/vdso/bits.h
> new file mode 100644
> index 000000000000..6d005a1f5d94
> --- /dev/null
> +++ b/tools/include/vdso/bits.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __VDSO_BITS_H
> +#define __VDSO_BITS_H
> +
> +#include <vdso/const.h>
> +
> +#define BIT(nr)			(UL(1) << (nr))
> +
> +#endif	/* __VDSO_BITS_H */
> diff --git a/tools/perf/check-headers.sh b/tools/perf/check-headers.sh
> index c905c683606a..cf147db4e5ca 100755
> --- a/tools/perf/check-headers.sh
> +++ b/tools/perf/check-headers.sh
> @@ -22,6 +22,7 @@ include/uapi/linux/usbdevice_fs.h
>  include/uapi/linux/vhost.h
>  include/uapi/sound/asound.h
>  include/linux/bits.h
> +include/vdso/bits.h
>  include/linux/const.h
>  include/vdso/const.h
>  include/linux/hash.h
> @@ -116,6 +117,7 @@ check arch/x86/lib/memcpy_64.S        '-I "^EXPORT_SYMBOL" -I "^#include <asm/ex
>  check arch/x86/lib/memset_64.S        '-I "^EXPORT_SYMBOL" -I "^#include <asm/export.h>" -I"^SYM_FUNC_START\(_LOCAL\)*(memset_\(erms\|orig\))"'
>  check include/uapi/asm-generic/mman.h '-I "^#include <\(uapi/\)*asm-generic/mman-common\(-tools\)*.h>"'
>  check include/uapi/linux/mman.h       '-I "^#include <\(uapi/\)*asm/mman.h>"'
> +check include/linux/build_bug.h       '-I "^#\(ifndef\|endif\)\( \/\/\)* static_assert$"'
>  check include/linux/ctype.h	      '-I "isdigit("'
>  check lib/ctype.c		      '-I "^EXPORT_SYMBOL" -I "^#include <linux/export.h>" -B'
>  check arch/x86/include/asm/inat.h     '-I "^#include [\"<]\(asm/\)*inat_types.h[\">]"'
> 

-- 
Regards,
Vincenzo