1 /* 2 * Copyright (c) 2016-2018, Intel Corporation 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions are met: 6 * 7 * * Redistributions of source code must retain the above copyright notice, 8 * this list of conditions and the following disclaimer. 9 * * Redistributions in binary form must reproduce the above copyright notice, 10 * this list of conditions and the following disclaimer in the documentation 11 * and/or other materials provided with the distribution. 12 * * Neither the name of Intel Corporation nor the names of its contributors 13 * may be used to endorse or promote products derived from this software 14 * without specific prior written permission. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #ifndef PT_BLOCK_CACHE_H 30 #define PT_BLOCK_CACHE_H 31 32 #include "intel-pt.h" 33 34 #include <stdint.h> 35 36 37 /* A block cache entry qualifier. 38 * 39 * This describes what to do at the decision point determined by a block cache 40 * entry. 41 */ 42 enum pt_bcache_qualifier { 43 /* This is not a decision point. 44 * 45 * The next decision point is too far away and one or more fields 46 * threatened to overflow so we had to stop somewhere on our way. 47 * 48 * Apply the displacement and number of instructions and continue from 49 * the resulting IP. 50 */ 51 ptbq_again, 52 53 /* The decision point is a conditional branch. 54 * 55 * This requires a conditional branch query. 56 * 57 * The isize field should provide the size of the branch instruction so 58 * only taken branches require the instruction to be decoded. 59 */ 60 ptbq_cond, 61 62 /* The decision point is a near indirect call. 63 * 64 * This requires a return-address stack update and an indirect branch 65 * query. 66 * 67 * The isize field should provide the size of the call instruction so 68 * the return address can be computed by adding it to the displacement 69 * that brings us to the call instruction. 70 * 71 * No instruction decode is required. 72 */ 73 ptbq_ind_call, 74 75 /* The decision point is a near return. 76 * 77 * The return may be compressed so this requires a conditional branch 78 * query to determine the compression state and either a return-address 79 * stack lookup or an indirect branch query. 80 * 81 * No instruction decode is required. 82 */ 83 ptbq_return, 84 85 /* The decision point is an indirect jump or far branch. 86 * 87 * This requires an indirect branch query. 88 * 89 * No instruction decode is required. 90 */ 91 ptbq_indirect, 92 93 /* The decision point requires the instruction at the decision point IP 94 * to be decoded to determine the next step. 95 * 96 * This is used for 97 * 98 * - near direct calls that need to maintain the return-address stack. 99 * 100 * - near direct jumps that are too far away to be handled with a 101 * block cache entry as they would overflow the displacement field. 102 */ 103 ptbq_decode 104 }; 105 106 /* A block cache entry. 107 * 108 * There will be one such entry per byte of decoded memory image. Each entry 109 * corresponds to an IP in the traced memory image. The cache is initialized 110 * with invalid entries for all IPs. 111 * 112 * Only entries for the first byte of each instruction will be used; other 113 * entries are ignored and will remain invalid. 114 * 115 * Each valid entry gives the distance from the entry's IP to the next decision 116 * point both in bytes and in the number of instructions. 117 */ 118 struct pt_bcache_entry { 119 /* The displacement to the next decision point in bytes. 120 * 121 * This is zero if we are at a decision point except for ptbq_again 122 * where it gives the displacement to the next block cache entry to be 123 * used. 124 */ 125 int32_t displacement:16; 126 127 /* The number of instructions to the next decision point. 128 * 129 * This is typically one at a decision point since we are already 130 * accounting for the instruction at the decision point. 131 * 132 * Note that this field must be smaller than the respective struct 133 * pt_block field so we can fit one block cache entry into an empty 134 * block. 135 */ 136 uint32_t ninsn:8; 137 138 /* The execution mode for all instruction between here and the next 139 * decision point. 140 * 141 * This is enum pt_exec_mode. 142 * 143 * This is ptem_unknown if the entry is not valid. 144 */ 145 uint32_t mode:2; 146 147 /* The decision point qualifier. 148 * 149 * This is enum pt_bcache_qualifier. 150 */ 151 uint32_t qualifier:3; 152 153 /* The size of the instruction at the decision point. 154 * 155 * This is zero if the size is too big to fit into the field. In this 156 * case, the instruction needs to be decoded to determine its size. 157 */ 158 uint32_t isize:3; 159 }; 160 161 /* Get the execution mode of a block cache entry. */ 162 static inline enum pt_exec_mode pt_bce_exec_mode(struct pt_bcache_entry bce) 163 { 164 return (enum pt_exec_mode) bce.mode; 165 } 166 167 /* Get the block cache qualifier of a block cache entry. */ 168 static inline enum pt_bcache_qualifier 169 pt_bce_qualifier(struct pt_bcache_entry bce) 170 { 171 return (enum pt_bcache_qualifier) bce.qualifier; 172 } 173 174 /* Check if a block cache entry is valid. */ 175 static inline int pt_bce_is_valid(struct pt_bcache_entry bce) 176 { 177 return pt_bce_exec_mode(bce) != ptem_unknown; 178 } 179 180 181 182 /* A block cache. */ 183 struct pt_block_cache { 184 /* The number of cache entries. */ 185 uint32_t nentries; 186 187 /* A variable-length array of @nentries entries. */ 188 struct pt_bcache_entry entry[]; 189 }; 190 191 /* Create a block cache. 192 * 193 * @nentries is the number of entries in the cache and should match the size of 194 * the to-be-cached section in bytes. 195 */ 196 extern struct pt_block_cache *pt_bcache_alloc(uint64_t nentries); 197 198 /* Destroy a block cache. */ 199 extern void pt_bcache_free(struct pt_block_cache *bcache); 200 201 /* Cache a block. 202 * 203 * It is expected that all calls for the same @index write the same @bce. 204 * 205 * Returns zero on success, a negative error code otherwise. 206 * Returns -pte_internal if @bcache is NULL. 207 * Returns -pte_internal if @index is outside of @bcache. 208 */ 209 extern int pt_bcache_add(struct pt_block_cache *bcache, uint64_t index, 210 struct pt_bcache_entry bce); 211 212 /* Lookup a cached block. 213 * 214 * The returned cache entry need not be valid. The caller is expected to check 215 * for validity using pt_bce_is_valid(*@bce). 216 * 217 * Returns zero on success, a negative error code otherwise. 218 * Returns -pte_internal if @bcache or @bce is NULL. 219 * Returns -pte_internal if @index is outside of @bcache. 220 */ 221 extern int pt_bcache_lookup(struct pt_bcache_entry *bce, 222 const struct pt_block_cache *bcache, 223 uint64_t index); 224 225 #endif /* PT_BLOCK_CACHE_H */ 226