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linux-next/kernel/kcsan/encoding.h
Marco Elver 5c36142574 kcsan: Prefer __always_inline for fast-path
Prefer __always_inline for fast-path functions that are called outside
of user_access_save, to avoid generating UACCESS warnings when
optimizing for size (CC_OPTIMIZE_FOR_SIZE). It will also avoid future
surprises with compiler versions that change the inlining heuristic even
when optimizing for performance.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/58708908-84a0-0a81-a836-ad97e33dbb62@infradead.org
2020-03-21 09:40:19 +01:00

96 lines
2.8 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _KERNEL_KCSAN_ENCODING_H
#define _KERNEL_KCSAN_ENCODING_H
#include <linux/bits.h>
#include <linux/log2.h>
#include <linux/mm.h>
#include "kcsan.h"
#define SLOT_RANGE PAGE_SIZE
#define INVALID_WATCHPOINT 0
#define CONSUMED_WATCHPOINT 1
/*
* The maximum useful size of accesses for which we set up watchpoints is the
* max range of slots we check on an access.
*/
#define MAX_ENCODABLE_SIZE (SLOT_RANGE * (1 + KCSAN_CHECK_ADJACENT))
/*
* Number of bits we use to store size info.
*/
#define WATCHPOINT_SIZE_BITS bits_per(MAX_ENCODABLE_SIZE)
/*
* This encoding for addresses discards the upper (1 for is-write + SIZE_BITS);
* however, most 64-bit architectures do not use the full 64-bit address space.
* Also, in order for a false positive to be observable 2 things need to happen:
*
* 1. different addresses but with the same encoded address race;
* 2. and both map onto the same watchpoint slots;
*
* Both these are assumed to be very unlikely. However, in case it still happens
* happens, the report logic will filter out the false positive (see report.c).
*/
#define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1 - WATCHPOINT_SIZE_BITS)
/*
* Masks to set/retrieve the encoded data.
*/
#define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1)
#define WATCHPOINT_SIZE_MASK \
GENMASK(BITS_PER_LONG-2, BITS_PER_LONG-2 - WATCHPOINT_SIZE_BITS)
#define WATCHPOINT_ADDR_MASK \
GENMASK(BITS_PER_LONG-3 - WATCHPOINT_SIZE_BITS, 0)
static inline bool check_encodable(unsigned long addr, size_t size)
{
return size <= MAX_ENCODABLE_SIZE;
}
static inline long
encode_watchpoint(unsigned long addr, size_t size, bool is_write)
{
return (long)((is_write ? WATCHPOINT_WRITE_MASK : 0) |
(size << WATCHPOINT_ADDR_BITS) |
(addr & WATCHPOINT_ADDR_MASK));
}
static __always_inline bool decode_watchpoint(long watchpoint,
unsigned long *addr_masked,
size_t *size,
bool *is_write)
{
if (watchpoint == INVALID_WATCHPOINT ||
watchpoint == CONSUMED_WATCHPOINT)
return false;
*addr_masked = (unsigned long)watchpoint & WATCHPOINT_ADDR_MASK;
*size = ((unsigned long)watchpoint & WATCHPOINT_SIZE_MASK) >> WATCHPOINT_ADDR_BITS;
*is_write = !!((unsigned long)watchpoint & WATCHPOINT_WRITE_MASK);
return true;
}
/*
* Return watchpoint slot for an address.
*/
static __always_inline int watchpoint_slot(unsigned long addr)
{
return (addr / PAGE_SIZE) % CONFIG_KCSAN_NUM_WATCHPOINTS;
}
static __always_inline bool matching_access(unsigned long addr1, size_t size1,
unsigned long addr2, size_t size2)
{
unsigned long end_range1 = addr1 + size1 - 1;
unsigned long end_range2 = addr2 + size2 - 1;
return addr1 <= end_range2 && addr2 <= end_range1;
}
#endif /* _KERNEL_KCSAN_ENCODING_H */