linux_dsm_epyc7002/include/linux/nospec.h
Will Deacon 8fa80c503b nospec: Move array_index_nospec() parameter checking into separate macro
For architectures providing their own implementation of
array_index_mask_nospec() in asm/barrier.h, attempting to use WARN_ONCE() to
complain about out-of-range parameters using WARN_ON() results in a mess
of mutually-dependent include files.

Rather than unpick the dependencies, simply have the core code in nospec.h
perform the checking for us.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1517840166-15399-1-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-02-15 01:15:51 +01:00

79 lines
2.4 KiB
C

// SPDX-License-Identifier: GPL-2.0
// Copyright(c) 2018 Linus Torvalds. All rights reserved.
// Copyright(c) 2018 Alexei Starovoitov. All rights reserved.
// Copyright(c) 2018 Intel Corporation. All rights reserved.
#ifndef _LINUX_NOSPEC_H
#define _LINUX_NOSPEC_H
/**
* array_index_mask_nospec() - generate a ~0 mask when index < size, 0 otherwise
* @index: array element index
* @size: number of elements in array
*
* When @index is out of bounds (@index >= @size), the sign bit will be
* set. Extend the sign bit to all bits and invert, giving a result of
* zero for an out of bounds index, or ~0 if within bounds [0, @size).
*/
#ifndef array_index_mask_nospec
static inline unsigned long array_index_mask_nospec(unsigned long index,
unsigned long size)
{
/*
* Always calculate and emit the mask even if the compiler
* thinks the mask is not needed. The compiler does not take
* into account the value of @index under speculation.
*/
OPTIMIZER_HIDE_VAR(index);
return ~(long)(index | (size - 1UL - index)) >> (BITS_PER_LONG - 1);
}
#endif
/*
* Warn developers about inappropriate array_index_nospec() usage.
*
* Even if the CPU speculates past the WARN_ONCE branch, the
* sign bit of @index is taken into account when generating the
* mask.
*
* This warning is compiled out when the compiler can infer that
* @index and @size are less than LONG_MAX.
*/
#define array_index_mask_nospec_check(index, size) \
({ \
if (WARN_ONCE(index > LONG_MAX || size > LONG_MAX, \
"array_index_nospec() limited to range of [0, LONG_MAX]\n")) \
_mask = 0; \
else \
_mask = array_index_mask_nospec(index, size); \
_mask; \
})
/*
* array_index_nospec - sanitize an array index after a bounds check
*
* For a code sequence like:
*
* if (index < size) {
* index = array_index_nospec(index, size);
* val = array[index];
* }
*
* ...if the CPU speculates past the bounds check then
* array_index_nospec() will clamp the index within the range of [0,
* size).
*/
#define array_index_nospec(index, size) \
({ \
typeof(index) _i = (index); \
typeof(size) _s = (size); \
unsigned long _mask = array_index_mask_nospec_check(_i, _s); \
\
BUILD_BUG_ON(sizeof(_i) > sizeof(long)); \
BUILD_BUG_ON(sizeof(_s) > sizeof(long)); \
\
_i &= _mask; \
_i; \
})
#endif /* _LINUX_NOSPEC_H */