linux_dsm_epyc7002/include/uapi/linux/swab.h
Arnd Bergmann 7322dd755e byteswap: try to avoid __builtin_constant_p gcc bug
This is another attempt to avoid a regression in wwn_to_u64() after that
started using get_unaligned_be64(), which in turn ran into a bug on
gcc-4.9 through 6.1.

The regression got introduced due to the combination of two separate
workarounds (commits e3bde9568d: "include/linux/unaligned: force
inlining of byteswap operations" and ef3fb2422f: "scsi: fc: use
get/put_unaligned64 for wwn access") that each try to sidestep distinct
problems with gcc behavior (code growth and increased stack usage).

Unfortunately after both have been applied, a more serious gcc bug has
been uncovered, leading to incorrect object code that discards part of a
function and causes undefined behavior.

As part of this problem is how __builtin_constant_p gets evaluated on an
argument passed by reference into an inline function, this avoids the
use of __builtin_constant_p() for all architectures that set
CONFIG_ARCH_USE_BUILTIN_BSWAP.  Most architectures do not set
ARCH_SUPPORTS_OPTIMIZED_INLINING, which means they probably do not
suffer from the problem in the qla2xxx driver, but they might still run
into it elsewhere.

Both of the original workarounds were only merged in the 4.6 kernel, and
the bug that is fixed by this patch should only appear if both are
there, so we probably don't need to backport the fix.  On the other
hand, it works by simplifying the code path and should not have any
negative effects.

[arnd@arndb.de: fix older gcc warnings]
  (http://lkml.kernel.org/r/12243652.bxSxEgjgfk@wuerfel)
Link: https://lkml.org/lkml/headers/2016/4/12/1103
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70232
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646
Fixes: e3bde9568d ("include/linux/unaligned: force inlining of byteswap operations")
Fixes: ef3fb2422f ("scsi: fc: use get/put_unaligned64 for wwn access")
Link: http://lkml.kernel.org/r/1780465.XdtPJpi8Tt@wuerfel
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Josh Poimboeuf <jpoimboe@redhat.com> # on gcc-5.3
Tested-by: Quinn Tran <quinn.tran@qlogic.com>
Cc: Martin Jambor <mjambor@suse.cz>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Himanshu Madhani <himanshu.madhani@qlogic.com>
Cc: Jan Hubicka <hubicka@ucw.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-05-05 17:38:53 -07:00

295 lines
6.6 KiB
C

#ifndef _UAPI_LINUX_SWAB_H
#define _UAPI_LINUX_SWAB_H
#include <linux/types.h>
#include <linux/compiler.h>
#include <asm/swab.h>
/*
* casts are necessary for constants, because we never know how for sure
* how U/UL/ULL map to __u16, __u32, __u64. At least not in a portable way.
*/
#define ___constant_swab16(x) ((__u16)( \
(((__u16)(x) & (__u16)0x00ffU) << 8) | \
(((__u16)(x) & (__u16)0xff00U) >> 8)))
#define ___constant_swab32(x) ((__u32)( \
(((__u32)(x) & (__u32)0x000000ffUL) << 24) | \
(((__u32)(x) & (__u32)0x0000ff00UL) << 8) | \
(((__u32)(x) & (__u32)0x00ff0000UL) >> 8) | \
(((__u32)(x) & (__u32)0xff000000UL) >> 24)))
#define ___constant_swab64(x) ((__u64)( \
(((__u64)(x) & (__u64)0x00000000000000ffULL) << 56) | \
(((__u64)(x) & (__u64)0x000000000000ff00ULL) << 40) | \
(((__u64)(x) & (__u64)0x0000000000ff0000ULL) << 24) | \
(((__u64)(x) & (__u64)0x00000000ff000000ULL) << 8) | \
(((__u64)(x) & (__u64)0x000000ff00000000ULL) >> 8) | \
(((__u64)(x) & (__u64)0x0000ff0000000000ULL) >> 24) | \
(((__u64)(x) & (__u64)0x00ff000000000000ULL) >> 40) | \
(((__u64)(x) & (__u64)0xff00000000000000ULL) >> 56)))
#define ___constant_swahw32(x) ((__u32)( \
(((__u32)(x) & (__u32)0x0000ffffUL) << 16) | \
(((__u32)(x) & (__u32)0xffff0000UL) >> 16)))
#define ___constant_swahb32(x) ((__u32)( \
(((__u32)(x) & (__u32)0x00ff00ffUL) << 8) | \
(((__u32)(x) & (__u32)0xff00ff00UL) >> 8)))
/*
* Implement the following as inlines, but define the interface using
* macros to allow constant folding when possible:
* ___swab16, ___swab32, ___swab64, ___swahw32, ___swahb32
*/
static inline __attribute_const__ __u16 __fswab16(__u16 val)
{
#if defined (__arch_swab16)
return __arch_swab16(val);
#else
return ___constant_swab16(val);
#endif
}
static inline __attribute_const__ __u32 __fswab32(__u32 val)
{
#if defined(__arch_swab32)
return __arch_swab32(val);
#else
return ___constant_swab32(val);
#endif
}
static inline __attribute_const__ __u64 __fswab64(__u64 val)
{
#if defined (__arch_swab64)
return __arch_swab64(val);
#elif defined(__SWAB_64_THRU_32__)
__u32 h = val >> 32;
__u32 l = val & ((1ULL << 32) - 1);
return (((__u64)__fswab32(l)) << 32) | ((__u64)(__fswab32(h)));
#else
return ___constant_swab64(val);
#endif
}
static inline __attribute_const__ __u32 __fswahw32(__u32 val)
{
#ifdef __arch_swahw32
return __arch_swahw32(val);
#else
return ___constant_swahw32(val);
#endif
}
static inline __attribute_const__ __u32 __fswahb32(__u32 val)
{
#ifdef __arch_swahb32
return __arch_swahb32(val);
#else
return ___constant_swahb32(val);
#endif
}
/**
* __swab16 - return a byteswapped 16-bit value
* @x: value to byteswap
*/
#ifdef __HAVE_BUILTIN_BSWAP16__
#define __swab16(x) (__u16)__builtin_bswap16((__u16)(x))
#else
#define __swab16(x) \
(__builtin_constant_p((__u16)(x)) ? \
___constant_swab16(x) : \
__fswab16(x))
#endif
/**
* __swab32 - return a byteswapped 32-bit value
* @x: value to byteswap
*/
#ifdef __HAVE_BUILTIN_BSWAP32__
#define __swab32(x) (__u32)__builtin_bswap32((__u32)(x))
#else
#define __swab32(x) \
(__builtin_constant_p((__u32)(x)) ? \
___constant_swab32(x) : \
__fswab32(x))
#endif
/**
* __swab64 - return a byteswapped 64-bit value
* @x: value to byteswap
*/
#ifdef __HAVE_BUILTIN_BSWAP64__
#define __swab64(x) (__u64)__builtin_bswap64((__u64)(x))
#else
#define __swab64(x) \
(__builtin_constant_p((__u64)(x)) ? \
___constant_swab64(x) : \
__fswab64(x))
#endif
/**
* __swahw32 - return a word-swapped 32-bit value
* @x: value to wordswap
*
* __swahw32(0x12340000) is 0x00001234
*/
#define __swahw32(x) \
(__builtin_constant_p((__u32)(x)) ? \
___constant_swahw32(x) : \
__fswahw32(x))
/**
* __swahb32 - return a high and low byte-swapped 32-bit value
* @x: value to byteswap
*
* __swahb32(0x12345678) is 0x34127856
*/
#define __swahb32(x) \
(__builtin_constant_p((__u32)(x)) ? \
___constant_swahb32(x) : \
__fswahb32(x))
/**
* __swab16p - return a byteswapped 16-bit value from a pointer
* @p: pointer to a naturally-aligned 16-bit value
*/
static __always_inline __u16 __swab16p(const __u16 *p)
{
#ifdef __arch_swab16p
return __arch_swab16p(p);
#else
return __swab16(*p);
#endif
}
/**
* __swab32p - return a byteswapped 32-bit value from a pointer
* @p: pointer to a naturally-aligned 32-bit value
*/
static __always_inline __u32 __swab32p(const __u32 *p)
{
#ifdef __arch_swab32p
return __arch_swab32p(p);
#else
return __swab32(*p);
#endif
}
/**
* __swab64p - return a byteswapped 64-bit value from a pointer
* @p: pointer to a naturally-aligned 64-bit value
*/
static __always_inline __u64 __swab64p(const __u64 *p)
{
#ifdef __arch_swab64p
return __arch_swab64p(p);
#else
return __swab64(*p);
#endif
}
/**
* __swahw32p - return a wordswapped 32-bit value from a pointer
* @p: pointer to a naturally-aligned 32-bit value
*
* See __swahw32() for details of wordswapping.
*/
static inline __u32 __swahw32p(const __u32 *p)
{
#ifdef __arch_swahw32p
return __arch_swahw32p(p);
#else
return __swahw32(*p);
#endif
}
/**
* __swahb32p - return a high and low byteswapped 32-bit value from a pointer
* @p: pointer to a naturally-aligned 32-bit value
*
* See __swahb32() for details of high/low byteswapping.
*/
static inline __u32 __swahb32p(const __u32 *p)
{
#ifdef __arch_swahb32p
return __arch_swahb32p(p);
#else
return __swahb32(*p);
#endif
}
/**
* __swab16s - byteswap a 16-bit value in-place
* @p: pointer to a naturally-aligned 16-bit value
*/
static inline void __swab16s(__u16 *p)
{
#ifdef __arch_swab16s
__arch_swab16s(p);
#else
*p = __swab16p(p);
#endif
}
/**
* __swab32s - byteswap a 32-bit value in-place
* @p: pointer to a naturally-aligned 32-bit value
*/
static __always_inline void __swab32s(__u32 *p)
{
#ifdef __arch_swab32s
__arch_swab32s(p);
#else
*p = __swab32p(p);
#endif
}
/**
* __swab64s - byteswap a 64-bit value in-place
* @p: pointer to a naturally-aligned 64-bit value
*/
static __always_inline void __swab64s(__u64 *p)
{
#ifdef __arch_swab64s
__arch_swab64s(p);
#else
*p = __swab64p(p);
#endif
}
/**
* __swahw32s - wordswap a 32-bit value in-place
* @p: pointer to a naturally-aligned 32-bit value
*
* See __swahw32() for details of wordswapping
*/
static inline void __swahw32s(__u32 *p)
{
#ifdef __arch_swahw32s
__arch_swahw32s(p);
#else
*p = __swahw32p(p);
#endif
}
/**
* __swahb32s - high and low byteswap a 32-bit value in-place
* @p: pointer to a naturally-aligned 32-bit value
*
* See __swahb32() for details of high and low byte swapping
*/
static inline void __swahb32s(__u32 *p)
{
#ifdef __arch_swahb32s
__arch_swahb32s(p);
#else
*p = __swahb32p(p);
#endif
}
#endif /* _UAPI_LINUX_SWAB_H */