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/*
* Copyright (c) 2016-2019, Intel Corporation
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* * Neither the name of Intel Corporation nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef PT_BLOCK_CACHE_H
#define PT_BLOCK_CACHE_H
#include "intel-pt.h"
#include <stdint.h>
/* A block cache entry qualifier.
*
* This describes what to do at the decision point determined by a block cache
* entry.
*/
enum pt_bcache_qualifier {
/* This is not a decision point.
*
* The next decision point is too far away and one or more fields
* threatened to overflow so we had to stop somewhere on our way.
*
* Apply the displacement and number of instructions and continue from
* the resulting IP.
*/
ptbq_again,
/* The decision point is a conditional branch.
*
* This requires a conditional branch query.
*
* The isize field should provide the size of the branch instruction so
* only taken branches require the instruction to be decoded.
*/
ptbq_cond,
/* The decision point is a near indirect call.
*
* This requires a return-address stack update and an indirect branch
* query.
*
* The isize field should provide the size of the call instruction so
* the return address can be computed by adding it to the displacement
* that brings us to the call instruction.
*
* No instruction decode is required.
*/
ptbq_ind_call,
/* The decision point is a near return.
*
* The return may be compressed so this requires a conditional branch
* query to determine the compression state and either a return-address
* stack lookup or an indirect branch query.
*
* No instruction decode is required.
*/
ptbq_return,
/* The decision point is an indirect jump or far branch.
*
* This requires an indirect branch query.
*
* No instruction decode is required.
*/
ptbq_indirect,
/* The decision point requires the instruction at the decision point IP
* to be decoded to determine the next step.
*
* This is used for
*
* - near direct calls that need to maintain the return-address stack.
*
* - near direct jumps that are too far away to be handled with a
* block cache entry as they would overflow the displacement field.
*/
ptbq_decode
};
/* A block cache entry.
*
* There will be one such entry per byte of decoded memory image. Each entry
* corresponds to an IP in the traced memory image. The cache is initialized
* with invalid entries for all IPs.
*
* Only entries for the first byte of each instruction will be used; other
* entries are ignored and will remain invalid.
*
* Each valid entry gives the distance from the entry's IP to the next decision
* point both in bytes and in the number of instructions.
*/
struct pt_bcache_entry {
/* The displacement to the next decision point in bytes.
*
* This is zero if we are at a decision point except for ptbq_again
* where it gives the displacement to the next block cache entry to be
* used.
*/
int32_t displacement:16;
/* The number of instructions to the next decision point.
*
* This is typically one at a decision point since we are already
* accounting for the instruction at the decision point.
*
* Note that this field must be smaller than the respective struct
* pt_block field so we can fit one block cache entry into an empty
* block.
*/
uint32_t ninsn:8;
/* The execution mode for all instruction between here and the next
* decision point.
*
* This is enum pt_exec_mode.
*
* This is ptem_unknown if the entry is not valid.
*/
uint32_t mode:2;
/* The decision point qualifier.
*
* This is enum pt_bcache_qualifier.
*/
uint32_t qualifier:3;
/* The size of the instruction at the decision point.
*
* This is zero if the size is too big to fit into the field. In this
* case, the instruction needs to be decoded to determine its size.
*/
uint32_t isize:3;
};
/* Get the execution mode of a block cache entry. */
static inline enum pt_exec_mode pt_bce_exec_mode(struct pt_bcache_entry bce)
{
return (enum pt_exec_mode) bce.mode;
}
/* Get the block cache qualifier of a block cache entry. */
static inline enum pt_bcache_qualifier
pt_bce_qualifier(struct pt_bcache_entry bce)
{
return (enum pt_bcache_qualifier) bce.qualifier;
}
/* Check if a block cache entry is valid. */
static inline int pt_bce_is_valid(struct pt_bcache_entry bce)
{
return pt_bce_exec_mode(bce) != ptem_unknown;
}
/* A block cache. */
struct pt_block_cache {
/* The number of cache entries. */
uint32_t nentries;
/* A variable-length array of @nentries entries. */
struct pt_bcache_entry entry[];
};
/* Create a block cache.
*
* @nentries is the number of entries in the cache and should match the size of
* the to-be-cached section in bytes.
*/
extern struct pt_block_cache *pt_bcache_alloc(uint64_t nentries);
/* Destroy a block cache. */
extern void pt_bcache_free(struct pt_block_cache *bcache);
/* Cache a block.
*
* It is expected that all calls for the same @index write the same @bce.
*
* Returns zero on success, a negative error code otherwise.
* Returns -pte_internal if @bcache is NULL.
* Returns -pte_internal if @index is outside of @bcache.
*/
extern int pt_bcache_add(struct pt_block_cache *bcache, uint64_t index,
struct pt_bcache_entry bce);
/* Lookup a cached block.
*
* The returned cache entry need not be valid. The caller is expected to check
* for validity using pt_bce_is_valid(*@bce).
*
* Returns zero on success, a negative error code otherwise.
* Returns -pte_internal if @bcache or @bce is NULL.
* Returns -pte_internal if @index is outside of @bcache.
*/
extern int pt_bcache_lookup(struct pt_bcache_entry *bce,
const struct pt_block_cache *bcache,
uint64_t index);
#endif /* PT_BLOCK_CACHE_H */
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