1 /* SFrame format description. 2 Copyright (C) 2022-2024 Free Software Foundation, Inc. 3 4 This file is part of libsframe. 5 6 libsframe is free software; you can redistribute it and/or modify it 7 under the terms of the GNU General Public License as published by the Free 8 Software Foundation; either version 3, or (at your option) any later 9 version. 10 11 This program is distributed in the hope that it will be useful, but 12 WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 14 See the GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program; see the file COPYING. If not see 18 <http://www.gnu.org/licenses/>. */ 19 20 #ifndef _SFRAME_H 21 #define _SFRAME_H 22 23 #include <sys/types.h> 24 #include <limits.h> 25 #include <stdint.h> 26 27 #include "ansidecl.h" 28 29 #ifdef __cplusplus 30 extern "C" 31 { 32 #endif 33 34 /* SFrame format. 35 36 SFrame format is a simple format to represent the information needed 37 for generating vanilla backtraces. SFrame format keeps track of the 38 minimal necessary information needed for stack tracing: 39 - Canonical Frame Address (CFA) 40 - Frame Pointer (FP) 41 - Return Address (RA) 42 43 The SFrame section itself has the following structure: 44 45 +--------+------------+---------+ 46 | file | function | frame | 47 | header | descriptor | row | 48 | | entries | entries | 49 +--------+------------+---------+ 50 51 The file header stores a magic number and version information, flags, and 52 the byte offset of each of the sections relative to the end of the header 53 itself. The file header also specifies the total number of Function 54 Descriptor Entries, Frame Row Entries and length of the FRE sub-section. 55 56 Following the header is a list of Function Descriptor Entries (FDEs). 57 This list may be sorted if the flags in the file header indicate it to be 58 so. The sort order, if applicable, is the order of functions in the 59 .text.* sections in the resulting binary artifact. Each Function 60 Descriptor Entry specifies the start PC of a function, the size in bytes 61 of the function and an offset to its first Frame Row Entry (FRE). Each FDE 62 additionally also specifies the type of FRE it uses to encode the stack 63 trace information. 64 65 Next, the SFrame Frame Row Entry sub-section is a list of variable size 66 records. Each entry represents stack trace information for a set of PCs 67 of the function. A singular Frame Row Entry is a self-sufficient record 68 which contains information on how to generate stack trace from the 69 applicable set of PCs. 70 71 */ 72 73 74 /* SFrame format versions. */ 75 #define SFRAME_VERSION_1 1 76 #define SFRAME_VERSION_2 2 77 /* SFrame magic number. */ 78 #define SFRAME_MAGIC 0xdee2 79 /* Current version of SFrame format. */ 80 #define SFRAME_VERSION SFRAME_VERSION_2 81 82 /* Various flags for SFrame. */ 83 84 /* Function Descriptor Entries are sorted on PC. */ 85 #define SFRAME_F_FDE_SORTED 0x1 86 /* Functions preserve frame pointer. */ 87 #define SFRAME_F_FRAME_POINTER 0x2 88 89 #define SFRAME_CFA_FIXED_FP_INVALID 0 90 #define SFRAME_CFA_FIXED_RA_INVALID 0 91 92 /* Supported ABIs/Arch. */ 93 #define SFRAME_ABI_AARCH64_ENDIAN_BIG 1 /* AARCH64 big endian. */ 94 #define SFRAME_ABI_AARCH64_ENDIAN_LITTLE 2 /* AARCH64 little endian. */ 95 #define SFRAME_ABI_AMD64_ENDIAN_LITTLE 3 /* AMD64 little endian. */ 96 97 /* SFrame FRE types. */ 98 #define SFRAME_FRE_TYPE_ADDR1 0 99 #define SFRAME_FRE_TYPE_ADDR2 1 100 #define SFRAME_FRE_TYPE_ADDR4 2 101 102 /* SFrame Function Descriptor Entry types. 103 104 The SFrame format has two possible representations for functions. The 105 choice of which type to use is made according to the instruction patterns 106 in the relevant program stub. 107 108 An SFrame FDE of type SFRAME_FDE_TYPE_PCINC is an indication 109 that the PCs in the FREs should be treated as increments in bytes. This is 110 used for a bulk of the executable code of a program, which contains 111 instructions with no specific pattern. 112 113 An SFrame FDE of type SFRAME_FDE_TYPE_PCMASK is an indication 114 that the PCs in the FREs should be treated as masks. This type is useful 115 for the cases when a small pattern of instructions in a program stub is 116 repeatedly to cover a specific functionality. Typical usescases are pltN 117 entries, trampolines etc. */ 118 119 /* Unwinders perform a (PC >= FRE_START_ADDR) to look up a matching FRE. */ 120 #define SFRAME_FDE_TYPE_PCINC 0 121 /* Unwinders perform a (PC % REP_BLOCK_SIZE >= FRE_START_ADDR) to look up a 122 matching FRE. */ 123 #define SFRAME_FDE_TYPE_PCMASK 1 124 125 typedef struct sframe_preamble 126 { 127 uint16_t sfp_magic; /* Magic number (SFRAME_MAGIC). */ 128 uint8_t sfp_version; /* Data format version number (SFRAME_VERSION). */ 129 uint8_t sfp_flags; /* Flags. */ 130 } ATTRIBUTE_PACKED sframe_preamble; 131 132 typedef struct sframe_header 133 { 134 sframe_preamble sfh_preamble; 135 /* Information about the arch (endianness) and ABI. */ 136 uint8_t sfh_abi_arch; 137 /* Offset for the Frame Pointer (FP) from CFA may be fixed for some 138 ABIs (e.g, in AMD64 when -fno-omit-frame-pointer is used). When fixed, 139 this field specifies the fixed stack frame offset and the individual 140 FREs do not need to track it. When not fixed, it is set to 141 SFRAME_CFA_FIXED_FP_INVALID, and the individual FREs may provide 142 the applicable stack frame offset, if any. */ 143 int8_t sfh_cfa_fixed_fp_offset; 144 /* Offset for the Return Address from CFA is fixed for some ABIs 145 (e.g., AMD64 has it as CFA-8). When fixed, the header specifies the 146 fixed stack frame offset and the individual FREs do not track it. When 147 not fixed, it is set to SFRAME_CFA_FIXED_RA_INVALID, and individual 148 FREs provide the applicable stack frame offset, if any. */ 149 int8_t sfh_cfa_fixed_ra_offset; 150 /* Number of bytes making up the auxiliary header, if any. 151 Some ABI/arch, in the future, may use this space for extending the 152 information in SFrame header. Auxiliary header is contained in 153 bytes sequentially following the sframe_header. */ 154 uint8_t sfh_auxhdr_len; 155 /* Number of SFrame FDEs in this SFrame section. */ 156 uint32_t sfh_num_fdes; 157 /* Number of SFrame Frame Row Entries. */ 158 uint32_t sfh_num_fres; 159 /* Number of bytes in the SFrame Frame Row Entry section. */ 160 uint32_t sfh_fre_len; 161 /* Offset of SFrame Function Descriptor Entry section. */ 162 uint32_t sfh_fdeoff; 163 /* Offset of SFrame Frame Row Entry section. */ 164 uint32_t sfh_freoff; 165 } ATTRIBUTE_PACKED sframe_header; 166 167 #define SFRAME_V1_HDR_SIZE(sframe_hdr) \ 168 ((sizeof (sframe_header) + (sframe_hdr).sfh_auxhdr_len)) 169 170 /* Two possible keys for executable (instruction) pointers signing. */ 171 #define SFRAME_AARCH64_PAUTH_KEY_A 0 /* Key A. */ 172 #define SFRAME_AARCH64_PAUTH_KEY_B 1 /* Key B. */ 173 174 typedef struct sframe_func_desc_entry 175 { 176 /* Function start address. Encoded as a signed offset, relative to the 177 beginning of the current FDE. */ 178 int32_t sfde_func_start_address; 179 /* Size of the function in bytes. */ 180 uint32_t sfde_func_size; 181 /* Offset of the first SFrame Frame Row Entry of the function, relative to the 182 beginning of the SFrame Frame Row Entry sub-section. */ 183 uint32_t sfde_func_start_fre_off; 184 /* Number of frame row entries for the function. */ 185 uint32_t sfde_func_num_fres; 186 /* Additional information for stack tracing from the function: 187 - 4-bits: Identify the FRE type used for the function. 188 - 1-bit: Identify the FDE type of the function - mask or inc. 189 - 1-bit: PAC authorization A/B key (aarch64). 190 - 2-bits: Unused. 191 ------------------------------------------------------------------------ 192 | Unused | PAC auth A/B key (aarch64) | FDE type | FRE type | 193 | | Unused (amd64) | | | 194 ------------------------------------------------------------------------ 195 8 6 5 4 0 */ 196 uint8_t sfde_func_info; 197 /* Size of the block of repeating insns. Used for SFrame FDEs of type 198 SFRAME_FDE_TYPE_PCMASK. */ 199 uint8_t sfde_func_rep_size; 200 uint16_t sfde_func_padding2; 201 } ATTRIBUTE_PACKED sframe_func_desc_entry; 202 203 /* Macros to compose and decompose function info in FDE. */ 204 205 /* Note: Set PAC auth key to SFRAME_AARCH64_PAUTH_KEY_A by default. */ 206 #define SFRAME_V1_FUNC_INFO(fde_type, fre_enc_type) \ 207 (((SFRAME_AARCH64_PAUTH_KEY_A & 0x1) << 5) | \ 208 (((fde_type) & 0x1) << 4) | ((fre_enc_type) & 0xf)) 209 210 #define SFRAME_V1_FUNC_FRE_TYPE(data) ((data) & 0xf) 211 #define SFRAME_V1_FUNC_FDE_TYPE(data) (((data) >> 4) & 0x1) 212 #define SFRAME_V1_FUNC_PAUTH_KEY(data) (((data) >> 5) & 0x1) 213 214 /* Set the pauth key as indicated. */ 215 #define SFRAME_V1_FUNC_INFO_UPDATE_PAUTH_KEY(pauth_key, fde_info) \ 216 ((((pauth_key) & 0x1) << 5) | ((fde_info) & 0xdf)) 217 218 /* Size of stack frame offsets in an SFrame Frame Row Entry. A single 219 SFrame FRE has all offsets of the same size. Offset size may vary 220 across frame row entries. */ 221 #define SFRAME_FRE_OFFSET_1B 0 222 #define SFRAME_FRE_OFFSET_2B 1 223 #define SFRAME_FRE_OFFSET_4B 2 224 225 /* An SFrame Frame Row Entry can be SP or FP based. */ 226 #define SFRAME_BASE_REG_FP 0 227 #define SFRAME_BASE_REG_SP 1 228 229 /* The index at which a specific offset is presented in the variable length 230 bytes of an FRE. */ 231 #define SFRAME_FRE_CFA_OFFSET_IDX 0 232 /* The RA stack offset, if present, will always be at index 1 in the variable 233 length bytes of the FRE. */ 234 #define SFRAME_FRE_RA_OFFSET_IDX 1 235 /* The FP stack offset may appear at offset 1 or 2, depending on the ABI as RA 236 may or may not be tracked. */ 237 #define SFRAME_FRE_FP_OFFSET_IDX 2 238 239 typedef struct sframe_fre_info 240 { 241 /* Information about 242 - 1 bit: base reg for CFA 243 - 4 bits: Number of offsets (N). A value of upto 3 is allowed to track 244 all three of CFA, FP and RA (fixed implicit order). 245 - 2 bits: information about size of the offsets (S) in bytes. 246 Valid values are SFRAME_FRE_OFFSET_1B, SFRAME_FRE_OFFSET_2B, 247 SFRAME_FRE_OFFSET_4B 248 - 1 bit: Mangled RA state bit (aarch64 only). 249 ---------------------------------------------------------------------------------- 250 | Mangled-RA (aarch64) | Size of offsets | Number of offsets | base_reg | 251 | Unused (amd64) | | | | 252 ---------------------------------------------------------------------------------- 253 8 7 5 1 0 254 255 */ 256 uint8_t fre_info; 257 } sframe_fre_info; 258 259 /* Macros to compose and decompose FRE info. */ 260 261 /* Note: Set mangled_ra_p to zero by default. */ 262 #define SFRAME_V1_FRE_INFO(base_reg_id, offset_num, offset_size) \ 263 (((0 & 0x1) << 7) | (((offset_size) & 0x3) << 5) | \ 264 (((offset_num) & 0xf) << 1) | ((base_reg_id) & 0x1)) 265 266 /* Set the mangled_ra_p bit as indicated. */ 267 #define SFRAME_V1_FRE_INFO_UPDATE_MANGLED_RA_P(mangled_ra_p, fre_info) \ 268 ((((mangled_ra_p) & 0x1) << 7) | ((fre_info) & 0x7f)) 269 270 #define SFRAME_V1_FRE_CFA_BASE_REG_ID(data) ((data) & 0x1) 271 #define SFRAME_V1_FRE_OFFSET_COUNT(data) (((data) >> 1) & 0xf) 272 #define SFRAME_V1_FRE_OFFSET_SIZE(data) (((data) >> 5) & 0x3) 273 #define SFRAME_V1_FRE_MANGLED_RA_P(data) (((data) >> 7) & 0x1) 274 275 /* SFrame Frame Row Entry definitions. 276 277 Used for both AMD64 and AARCH64. 278 279 An SFrame Frame Row Entry is a self-sufficient record which contains 280 information on how to generate the stack trace for the specified range of 281 PCs. Each SFrame Frame Row Entry is followed by S*N bytes, where: 282 S is the size of the stack frame offset for the FRE, and 283 N is the number of stack frame offsets in the FRE 284 285 The offsets are interpreted in order as follows: 286 287 offset1 (interpreted as CFA = BASE_REG + offset1) 288 289 if RA is being tracked 290 offset2 (interpreted as RA = CFA + offset2) 291 if FP is being tracked 292 offset3 (intrepreted as FP = CFA + offset2) 293 fi 294 else 295 if FP is being tracked 296 offset2 (intrepreted as FP = CFA + offset2) 297 fi 298 fi 299 */ 300 301 /* Used when SFRAME_FRE_TYPE_ADDR1 is specified as FRE type. */ 302 typedef struct sframe_frame_row_entry_addr1 303 { 304 /* Start address of the frame row entry. Encoded as an 1-byte unsigned 305 offset, relative to the start address of the function. */ 306 uint8_t sfre_start_address; 307 sframe_fre_info sfre_info; 308 } ATTRIBUTE_PACKED sframe_frame_row_entry_addr1; 309 310 /* Upper limit of start address in sframe_frame_row_entry_addr1 311 is 0x100 (not inclusive). */ 312 #define SFRAME_FRE_TYPE_ADDR1_LIMIT \ 313 (1ULL << ((SFRAME_FRE_TYPE_ADDR1 + 1) * 8)) 314 315 /* Used when SFRAME_FRE_TYPE_ADDR2 is specified as FRE type. */ 316 typedef struct sframe_frame_row_entry_addr2 317 { 318 /* Start address of the frame row entry. Encoded as an 2-byte unsigned 319 offset, relative to the start address of the function. */ 320 uint16_t sfre_start_address; 321 sframe_fre_info sfre_info; 322 } ATTRIBUTE_PACKED sframe_frame_row_entry_addr2; 323 324 /* Upper limit of start address in sframe_frame_row_entry_addr2 325 is 0x10000 (not inclusive). */ 326 #define SFRAME_FRE_TYPE_ADDR2_LIMIT \ 327 (1ULL << ((SFRAME_FRE_TYPE_ADDR2 * 2) * 8)) 328 329 /* Used when SFRAME_FRE_TYPE_ADDR4 is specified as FRE type. */ 330 typedef struct sframe_frame_row_entry_addr4 331 { 332 /* Start address of the frame row entry. Encoded as a 4-byte unsigned 333 offset, relative to the start address of the function. */ 334 uint32_t sfre_start_address; 335 sframe_fre_info sfre_info; 336 } ATTRIBUTE_PACKED sframe_frame_row_entry_addr4; 337 338 /* Upper limit of start address in sframe_frame_row_entry_addr2 339 is 0x100000000 (not inclusive). */ 340 #define SFRAME_FRE_TYPE_ADDR4_LIMIT \ 341 (1ULL << ((SFRAME_FRE_TYPE_ADDR4 * 2) * 8)) 342 343 #ifdef __cplusplus 344 } 345 #endif 346 347 #endif /* _SFRAME_H */ 348