1 /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ 2 #ifndef __BPF_CORE_READ_H__ 3 #define __BPF_CORE_READ_H__ 4 5 #include "bpf_helpers.h" 6 7 /* 8 * enum bpf_field_info_kind is passed as a second argument into 9 * __builtin_preserve_field_info() built-in to get a specific aspect of 10 * a field, captured as a first argument. __builtin_preserve_field_info(field, 11 * info_kind) returns __u32 integer and produces BTF field relocation, which 12 * is understood and processed by libbpf during BPF object loading. See 13 * selftests/bpf for examples. 14 */ 15 enum bpf_field_info_kind { 16 BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */ 17 BPF_FIELD_BYTE_SIZE = 1, 18 BPF_FIELD_EXISTS = 2, /* field existence in target kernel */ 19 BPF_FIELD_SIGNED = 3, 20 BPF_FIELD_LSHIFT_U64 = 4, 21 BPF_FIELD_RSHIFT_U64 = 5, 22 }; 23 24 /* second argument to __builtin_btf_type_id() built-in */ 25 enum bpf_type_id_kind { 26 BPF_TYPE_ID_LOCAL = 0, /* BTF type ID in local program */ 27 BPF_TYPE_ID_TARGET = 1, /* BTF type ID in target kernel */ 28 }; 29 30 /* second argument to __builtin_preserve_type_info() built-in */ 31 enum bpf_type_info_kind { 32 BPF_TYPE_EXISTS = 0, /* type existence in target kernel */ 33 BPF_TYPE_SIZE = 1, /* type size in target kernel */ 34 BPF_TYPE_MATCHES = 2, /* type match in target kernel */ 35 }; 36 37 /* second argument to __builtin_preserve_enum_value() built-in */ 38 enum bpf_enum_value_kind { 39 BPF_ENUMVAL_EXISTS = 0, /* enum value existence in kernel */ 40 BPF_ENUMVAL_VALUE = 1, /* enum value value relocation */ 41 }; 42 43 #define __CORE_RELO(src, field, info) \ 44 __builtin_preserve_field_info((src)->field, BPF_FIELD_##info) 45 46 #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ 47 #define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \ 48 bpf_probe_read_kernel( \ 49 (void *)dst, \ 50 __CORE_RELO(src, fld, BYTE_SIZE), \ 51 (const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET)) 52 #else 53 /* semantics of LSHIFT_64 assumes loading values into low-ordered bytes, so 54 * for big-endian we need to adjust destination pointer accordingly, based on 55 * field byte size 56 */ 57 #define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \ 58 bpf_probe_read_kernel( \ 59 (void *)dst + (8 - __CORE_RELO(src, fld, BYTE_SIZE)), \ 60 __CORE_RELO(src, fld, BYTE_SIZE), \ 61 (const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET)) 62 #endif 63 64 /* 65 * Extract bitfield, identified by s->field, and return its value as u64. 66 * All this is done in relocatable manner, so bitfield changes such as 67 * signedness, bit size, offset changes, this will be handled automatically. 68 * This version of macro is using bpf_probe_read_kernel() to read underlying 69 * integer storage. Macro functions as an expression and its return type is 70 * bpf_probe_read_kernel()'s return value: 0, on success, <0 on error. 71 */ 72 #define BPF_CORE_READ_BITFIELD_PROBED(s, field) ({ \ 73 unsigned long long val = 0; \ 74 \ 75 __CORE_BITFIELD_PROBE_READ(&val, s, field); \ 76 val <<= __CORE_RELO(s, field, LSHIFT_U64); \ 77 if (__CORE_RELO(s, field, SIGNED)) \ 78 val = ((long long)val) >> __CORE_RELO(s, field, RSHIFT_U64); \ 79 else \ 80 val = val >> __CORE_RELO(s, field, RSHIFT_U64); \ 81 val; \ 82 }) 83 84 /* 85 * Extract bitfield, identified by s->field, and return its value as u64. 86 * This version of macro is using direct memory reads and should be used from 87 * BPF program types that support such functionality (e.g., typed raw 88 * tracepoints). 89 */ 90 #define BPF_CORE_READ_BITFIELD(s, field) ({ \ 91 const void *p = (const void *)s + __CORE_RELO(s, field, BYTE_OFFSET); \ 92 unsigned long long val; \ 93 \ 94 /* This is a so-called barrier_var() operation that makes specified \ 95 * variable "a black box" for optimizing compiler. \ 96 * It forces compiler to perform BYTE_OFFSET relocation on p and use \ 97 * its calculated value in the switch below, instead of applying \ 98 * the same relocation 4 times for each individual memory load. \ 99 */ \ 100 asm volatile("" : "=r"(p) : "0"(p)); \ 101 \ 102 switch (__CORE_RELO(s, field, BYTE_SIZE)) { \ 103 case 1: val = *(const unsigned char *)p; break; \ 104 case 2: val = *(const unsigned short *)p; break; \ 105 case 4: val = *(const unsigned int *)p; break; \ 106 case 8: val = *(const unsigned long long *)p; break; \ 107 default: val = 0; break; \ 108 } \ 109 val <<= __CORE_RELO(s, field, LSHIFT_U64); \ 110 if (__CORE_RELO(s, field, SIGNED)) \ 111 val = ((long long)val) >> __CORE_RELO(s, field, RSHIFT_U64); \ 112 else \ 113 val = val >> __CORE_RELO(s, field, RSHIFT_U64); \ 114 val; \ 115 }) 116 117 /* 118 * Write to a bitfield, identified by s->field. 119 * This is the inverse of BPF_CORE_WRITE_BITFIELD(). 120 */ 121 #define BPF_CORE_WRITE_BITFIELD(s, field, new_val) ({ \ 122 void *p = (void *)s + __CORE_RELO(s, field, BYTE_OFFSET); \ 123 unsigned int byte_size = __CORE_RELO(s, field, BYTE_SIZE); \ 124 unsigned int lshift = __CORE_RELO(s, field, LSHIFT_U64); \ 125 unsigned int rshift = __CORE_RELO(s, field, RSHIFT_U64); \ 126 unsigned long long mask, val, nval = new_val; \ 127 unsigned int rpad = rshift - lshift; \ 128 \ 129 asm volatile("" : "+r"(p)); \ 130 \ 131 switch (byte_size) { \ 132 case 1: val = *(unsigned char *)p; break; \ 133 case 2: val = *(unsigned short *)p; break; \ 134 case 4: val = *(unsigned int *)p; break; \ 135 case 8: val = *(unsigned long long *)p; break; \ 136 } \ 137 \ 138 mask = (~0ULL << rshift) >> lshift; \ 139 val = (val & ~mask) | ((nval << rpad) & mask); \ 140 \ 141 switch (byte_size) { \ 142 case 1: *(unsigned char *)p = val; break; \ 143 case 2: *(unsigned short *)p = val; break; \ 144 case 4: *(unsigned int *)p = val; break; \ 145 case 8: *(unsigned long long *)p = val; break; \ 146 } \ 147 }) 148 149 /* Differentiator between compilers builtin implementations. This is a 150 * requirement due to the compiler parsing differences where GCC optimizes 151 * early in parsing those constructs of type pointers to the builtin specific 152 * type, resulting in not being possible to collect the required type 153 * information in the builtin expansion. 154 */ 155 #ifdef __clang__ 156 #define ___bpf_typeof(type) ((typeof(type) *) 0) 157 #else 158 #define ___bpf_typeof1(type, NR) ({ \ 159 extern typeof(type) *___concat(bpf_type_tmp_, NR); \ 160 ___concat(bpf_type_tmp_, NR); \ 161 }) 162 #define ___bpf_typeof(type) ___bpf_typeof1(type, __COUNTER__) 163 #endif 164 165 #ifdef __clang__ 166 #define ___bpf_field_ref1(field) (field) 167 #define ___bpf_field_ref2(type, field) (___bpf_typeof(type)->field) 168 #else 169 #define ___bpf_field_ref1(field) (&(field)) 170 #define ___bpf_field_ref2(type, field) (&(___bpf_typeof(type)->field)) 171 #endif 172 #define ___bpf_field_ref(args...) \ 173 ___bpf_apply(___bpf_field_ref, ___bpf_narg(args))(args) 174 175 /* 176 * Convenience macro to check that field actually exists in target kernel's. 177 * Returns: 178 * 1, if matching field is present in target kernel; 179 * 0, if no matching field found. 180 * 181 * Supports two forms: 182 * - field reference through variable access: 183 * bpf_core_field_exists(p->my_field); 184 * - field reference through type and field names: 185 * bpf_core_field_exists(struct my_type, my_field). 186 */ 187 #define bpf_core_field_exists(field...) \ 188 __builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_EXISTS) 189 190 /* 191 * Convenience macro to get the byte size of a field. Works for integers, 192 * struct/unions, pointers, arrays, and enums. 193 * 194 * Supports two forms: 195 * - field reference through variable access: 196 * bpf_core_field_size(p->my_field); 197 * - field reference through type and field names: 198 * bpf_core_field_size(struct my_type, my_field). 199 */ 200 #define bpf_core_field_size(field...) \ 201 __builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_BYTE_SIZE) 202 203 /* 204 * Convenience macro to get field's byte offset. 205 * 206 * Supports two forms: 207 * - field reference through variable access: 208 * bpf_core_field_offset(p->my_field); 209 * - field reference through type and field names: 210 * bpf_core_field_offset(struct my_type, my_field). 211 */ 212 #define bpf_core_field_offset(field...) \ 213 __builtin_preserve_field_info(___bpf_field_ref(field), BPF_FIELD_BYTE_OFFSET) 214 215 /* 216 * Convenience macro to get BTF type ID of a specified type, using a local BTF 217 * information. Return 32-bit unsigned integer with type ID from program's own 218 * BTF. Always succeeds. 219 */ 220 #define bpf_core_type_id_local(type) \ 221 __builtin_btf_type_id(*___bpf_typeof(type), BPF_TYPE_ID_LOCAL) 222 223 /* 224 * Convenience macro to get BTF type ID of a target kernel's type that matches 225 * specified local type. 226 * Returns: 227 * - valid 32-bit unsigned type ID in kernel BTF; 228 * - 0, if no matching type was found in a target kernel BTF. 229 */ 230 #define bpf_core_type_id_kernel(type) \ 231 __builtin_btf_type_id(*___bpf_typeof(type), BPF_TYPE_ID_TARGET) 232 233 /* 234 * Convenience macro to check that provided named type 235 * (struct/union/enum/typedef) exists in a target kernel. 236 * Returns: 237 * 1, if such type is present in target kernel's BTF; 238 * 0, if no matching type is found. 239 */ 240 #define bpf_core_type_exists(type) \ 241 __builtin_preserve_type_info(*___bpf_typeof(type), BPF_TYPE_EXISTS) 242 243 /* 244 * Convenience macro to check that provided named type 245 * (struct/union/enum/typedef) "matches" that in a target kernel. 246 * Returns: 247 * 1, if the type matches in the target kernel's BTF; 248 * 0, if the type does not match any in the target kernel 249 */ 250 #define bpf_core_type_matches(type) \ 251 __builtin_preserve_type_info(*___bpf_typeof(type), BPF_TYPE_MATCHES) 252 253 /* 254 * Convenience macro to get the byte size of a provided named type 255 * (struct/union/enum/typedef) in a target kernel. 256 * Returns: 257 * >= 0 size (in bytes), if type is present in target kernel's BTF; 258 * 0, if no matching type is found. 259 */ 260 #define bpf_core_type_size(type) \ 261 __builtin_preserve_type_info(*___bpf_typeof(type), BPF_TYPE_SIZE) 262 263 /* 264 * Convenience macro to check that provided enumerator value is defined in 265 * a target kernel. 266 * Returns: 267 * 1, if specified enum type and its enumerator value are present in target 268 * kernel's BTF; 269 * 0, if no matching enum and/or enum value within that enum is found. 270 */ 271 #ifdef __clang__ 272 #define bpf_core_enum_value_exists(enum_type, enum_value) \ 273 __builtin_preserve_enum_value(*(typeof(enum_type) *)enum_value, BPF_ENUMVAL_EXISTS) 274 #else 275 #define bpf_core_enum_value_exists(enum_type, enum_value) \ 276 __builtin_preserve_enum_value(___bpf_typeof(enum_type), enum_value, BPF_ENUMVAL_EXISTS) 277 #endif 278 279 /* 280 * Convenience macro to get the integer value of an enumerator value in 281 * a target kernel. 282 * Returns: 283 * 64-bit value, if specified enum type and its enumerator value are 284 * present in target kernel's BTF; 285 * 0, if no matching enum and/or enum value within that enum is found. 286 */ 287 #ifdef __clang__ 288 #define bpf_core_enum_value(enum_type, enum_value) \ 289 __builtin_preserve_enum_value(*(typeof(enum_type) *)enum_value, BPF_ENUMVAL_VALUE) 290 #else 291 #define bpf_core_enum_value(enum_type, enum_value) \ 292 __builtin_preserve_enum_value(___bpf_typeof(enum_type), enum_value, BPF_ENUMVAL_VALUE) 293 #endif 294 295 /* 296 * bpf_core_read() abstracts away bpf_probe_read_kernel() call and captures 297 * offset relocation for source address using __builtin_preserve_access_index() 298 * built-in, provided by Clang. 299 * 300 * __builtin_preserve_access_index() takes as an argument an expression of 301 * taking an address of a field within struct/union. It makes compiler emit 302 * a relocation, which records BTF type ID describing root struct/union and an 303 * accessor string which describes exact embedded field that was used to take 304 * an address. See detailed description of this relocation format and 305 * semantics in comments to struct bpf_core_relo in include/uapi/linux/bpf.h. 306 * 307 * This relocation allows libbpf to adjust BPF instruction to use correct 308 * actual field offset, based on target kernel BTF type that matches original 309 * (local) BTF, used to record relocation. 310 */ 311 #define bpf_core_read(dst, sz, src) \ 312 bpf_probe_read_kernel(dst, sz, (const void *)__builtin_preserve_access_index(src)) 313 314 /* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */ 315 #define bpf_core_read_user(dst, sz, src) \ 316 bpf_probe_read_user(dst, sz, (const void *)__builtin_preserve_access_index(src)) 317 /* 318 * bpf_core_read_str() is a thin wrapper around bpf_probe_read_str() 319 * additionally emitting BPF CO-RE field relocation for specified source 320 * argument. 321 */ 322 #define bpf_core_read_str(dst, sz, src) \ 323 bpf_probe_read_kernel_str(dst, sz, (const void *)__builtin_preserve_access_index(src)) 324 325 /* NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. */ 326 #define bpf_core_read_user_str(dst, sz, src) \ 327 bpf_probe_read_user_str(dst, sz, (const void *)__builtin_preserve_access_index(src)) 328 329 extern void *bpf_rdonly_cast(const void *obj, __u32 btf_id) __ksym __weak; 330 331 /* 332 * Cast provided pointer *ptr* into a pointer to a specified *type* in such 333 * a way that BPF verifier will become aware of associated kernel-side BTF 334 * type. This allows to access members of kernel types directly without the 335 * need to use BPF_CORE_READ() macros. 336 */ 337 #define bpf_core_cast(ptr, type) \ 338 ((typeof(type) *)bpf_rdonly_cast((ptr), bpf_core_type_id_kernel(type))) 339 340 #define ___concat(a, b) a ## b 341 #define ___apply(fn, n) ___concat(fn, n) 342 #define ___nth(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, __11, N, ...) N 343 344 /* 345 * return number of provided arguments; used for switch-based variadic macro 346 * definitions (see ___last, ___arrow, etc below) 347 */ 348 #define ___narg(...) ___nth(_, ##__VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) 349 /* 350 * return 0 if no arguments are passed, N - otherwise; used for 351 * recursively-defined macros to specify termination (0) case, and generic 352 * (N) case (e.g., ___read_ptrs, ___core_read) 353 */ 354 #define ___empty(...) ___nth(_, ##__VA_ARGS__, N, N, N, N, N, N, N, N, N, N, 0) 355 356 #define ___last1(x) x 357 #define ___last2(a, x) x 358 #define ___last3(a, b, x) x 359 #define ___last4(a, b, c, x) x 360 #define ___last5(a, b, c, d, x) x 361 #define ___last6(a, b, c, d, e, x) x 362 #define ___last7(a, b, c, d, e, f, x) x 363 #define ___last8(a, b, c, d, e, f, g, x) x 364 #define ___last9(a, b, c, d, e, f, g, h, x) x 365 #define ___last10(a, b, c, d, e, f, g, h, i, x) x 366 #define ___last(...) ___apply(___last, ___narg(__VA_ARGS__))(__VA_ARGS__) 367 368 #define ___nolast2(a, _) a 369 #define ___nolast3(a, b, _) a, b 370 #define ___nolast4(a, b, c, _) a, b, c 371 #define ___nolast5(a, b, c, d, _) a, b, c, d 372 #define ___nolast6(a, b, c, d, e, _) a, b, c, d, e 373 #define ___nolast7(a, b, c, d, e, f, _) a, b, c, d, e, f 374 #define ___nolast8(a, b, c, d, e, f, g, _) a, b, c, d, e, f, g 375 #define ___nolast9(a, b, c, d, e, f, g, h, _) a, b, c, d, e, f, g, h 376 #define ___nolast10(a, b, c, d, e, f, g, h, i, _) a, b, c, d, e, f, g, h, i 377 #define ___nolast(...) ___apply(___nolast, ___narg(__VA_ARGS__))(__VA_ARGS__) 378 379 #define ___arrow1(a) a 380 #define ___arrow2(a, b) a->b 381 #define ___arrow3(a, b, c) a->b->c 382 #define ___arrow4(a, b, c, d) a->b->c->d 383 #define ___arrow5(a, b, c, d, e) a->b->c->d->e 384 #define ___arrow6(a, b, c, d, e, f) a->b->c->d->e->f 385 #define ___arrow7(a, b, c, d, e, f, g) a->b->c->d->e->f->g 386 #define ___arrow8(a, b, c, d, e, f, g, h) a->b->c->d->e->f->g->h 387 #define ___arrow9(a, b, c, d, e, f, g, h, i) a->b->c->d->e->f->g->h->i 388 #define ___arrow10(a, b, c, d, e, f, g, h, i, j) a->b->c->d->e->f->g->h->i->j 389 #define ___arrow(...) ___apply(___arrow, ___narg(__VA_ARGS__))(__VA_ARGS__) 390 391 #define ___type(...) typeof(___arrow(__VA_ARGS__)) 392 393 #define ___read(read_fn, dst, src_type, src, accessor) \ 394 read_fn((void *)(dst), sizeof(*(dst)), &((src_type)(src))->accessor) 395 396 /* "recursively" read a sequence of inner pointers using local __t var */ 397 #define ___rd_first(fn, src, a) ___read(fn, &__t, ___type(src), src, a); 398 #define ___rd_last(fn, ...) \ 399 ___read(fn, &__t, ___type(___nolast(__VA_ARGS__)), __t, ___last(__VA_ARGS__)); 400 #define ___rd_p1(fn, ...) const void *__t; ___rd_first(fn, __VA_ARGS__) 401 #define ___rd_p2(fn, ...) ___rd_p1(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 402 #define ___rd_p3(fn, ...) ___rd_p2(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 403 #define ___rd_p4(fn, ...) ___rd_p3(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 404 #define ___rd_p5(fn, ...) ___rd_p4(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 405 #define ___rd_p6(fn, ...) ___rd_p5(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 406 #define ___rd_p7(fn, ...) ___rd_p6(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 407 #define ___rd_p8(fn, ...) ___rd_p7(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 408 #define ___rd_p9(fn, ...) ___rd_p8(fn, ___nolast(__VA_ARGS__)) ___rd_last(fn, __VA_ARGS__) 409 #define ___read_ptrs(fn, src, ...) \ 410 ___apply(___rd_p, ___narg(__VA_ARGS__))(fn, src, __VA_ARGS__) 411 412 #define ___core_read0(fn, fn_ptr, dst, src, a) \ 413 ___read(fn, dst, ___type(src), src, a); 414 #define ___core_readN(fn, fn_ptr, dst, src, ...) \ 415 ___read_ptrs(fn_ptr, src, ___nolast(__VA_ARGS__)) \ 416 ___read(fn, dst, ___type(src, ___nolast(__VA_ARGS__)), __t, \ 417 ___last(__VA_ARGS__)); 418 #define ___core_read(fn, fn_ptr, dst, src, a, ...) \ 419 ___apply(___core_read, ___empty(__VA_ARGS__))(fn, fn_ptr, dst, \ 420 src, a, ##__VA_ARGS__) 421 422 /* 423 * BPF_CORE_READ_INTO() is a more performance-conscious variant of 424 * BPF_CORE_READ(), in which final field is read into user-provided storage. 425 * See BPF_CORE_READ() below for more details on general usage. 426 */ 427 #define BPF_CORE_READ_INTO(dst, src, a, ...) ({ \ 428 ___core_read(bpf_core_read, bpf_core_read, \ 429 dst, (src), a, ##__VA_ARGS__) \ 430 }) 431 432 /* 433 * Variant of BPF_CORE_READ_INTO() for reading from user-space memory. 434 * 435 * NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. 436 */ 437 #define BPF_CORE_READ_USER_INTO(dst, src, a, ...) ({ \ 438 ___core_read(bpf_core_read_user, bpf_core_read_user, \ 439 dst, (src), a, ##__VA_ARGS__) \ 440 }) 441 442 /* Non-CO-RE variant of BPF_CORE_READ_INTO() */ 443 #define BPF_PROBE_READ_INTO(dst, src, a, ...) ({ \ 444 ___core_read(bpf_probe_read_kernel, bpf_probe_read_kernel, \ 445 dst, (src), a, ##__VA_ARGS__) \ 446 }) 447 448 /* Non-CO-RE variant of BPF_CORE_READ_USER_INTO(). 449 * 450 * As no CO-RE relocations are emitted, source types can be arbitrary and are 451 * not restricted to kernel types only. 452 */ 453 #define BPF_PROBE_READ_USER_INTO(dst, src, a, ...) ({ \ 454 ___core_read(bpf_probe_read_user, bpf_probe_read_user, \ 455 dst, (src), a, ##__VA_ARGS__) \ 456 }) 457 458 /* 459 * BPF_CORE_READ_STR_INTO() does same "pointer chasing" as 460 * BPF_CORE_READ() for intermediate pointers, but then executes (and returns 461 * corresponding error code) bpf_core_read_str() for final string read. 462 */ 463 #define BPF_CORE_READ_STR_INTO(dst, src, a, ...) ({ \ 464 ___core_read(bpf_core_read_str, bpf_core_read, \ 465 dst, (src), a, ##__VA_ARGS__) \ 466 }) 467 468 /* 469 * Variant of BPF_CORE_READ_STR_INTO() for reading from user-space memory. 470 * 471 * NOTE: see comments for BPF_CORE_READ_USER() about the proper types use. 472 */ 473 #define BPF_CORE_READ_USER_STR_INTO(dst, src, a, ...) ({ \ 474 ___core_read(bpf_core_read_user_str, bpf_core_read_user, \ 475 dst, (src), a, ##__VA_ARGS__) \ 476 }) 477 478 /* Non-CO-RE variant of BPF_CORE_READ_STR_INTO() */ 479 #define BPF_PROBE_READ_STR_INTO(dst, src, a, ...) ({ \ 480 ___core_read(bpf_probe_read_kernel_str, bpf_probe_read_kernel, \ 481 dst, (src), a, ##__VA_ARGS__) \ 482 }) 483 484 /* 485 * Non-CO-RE variant of BPF_CORE_READ_USER_STR_INTO(). 486 * 487 * As no CO-RE relocations are emitted, source types can be arbitrary and are 488 * not restricted to kernel types only. 489 */ 490 #define BPF_PROBE_READ_USER_STR_INTO(dst, src, a, ...) ({ \ 491 ___core_read(bpf_probe_read_user_str, bpf_probe_read_user, \ 492 dst, (src), a, ##__VA_ARGS__) \ 493 }) 494 495 /* 496 * BPF_CORE_READ() is used to simplify BPF CO-RE relocatable read, especially 497 * when there are few pointer chasing steps. 498 * E.g., what in non-BPF world (or in BPF w/ BCC) would be something like: 499 * int x = s->a.b.c->d.e->f->g; 500 * can be succinctly achieved using BPF_CORE_READ as: 501 * int x = BPF_CORE_READ(s, a.b.c, d.e, f, g); 502 * 503 * BPF_CORE_READ will decompose above statement into 4 bpf_core_read (BPF 504 * CO-RE relocatable bpf_probe_read_kernel() wrapper) calls, logically 505 * equivalent to: 506 * 1. const void *__t = s->a.b.c; 507 * 2. __t = __t->d.e; 508 * 3. __t = __t->f; 509 * 4. return __t->g; 510 * 511 * Equivalence is logical, because there is a heavy type casting/preservation 512 * involved, as well as all the reads are happening through 513 * bpf_probe_read_kernel() calls using __builtin_preserve_access_index() to 514 * emit CO-RE relocations. 515 * 516 * N.B. Only up to 9 "field accessors" are supported, which should be more 517 * than enough for any practical purpose. 518 */ 519 #define BPF_CORE_READ(src, a, ...) ({ \ 520 ___type((src), a, ##__VA_ARGS__) __r; \ 521 BPF_CORE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \ 522 __r; \ 523 }) 524 525 /* 526 * Variant of BPF_CORE_READ() for reading from user-space memory. 527 * 528 * NOTE: all the source types involved are still *kernel types* and need to 529 * exist in kernel (or kernel module) BTF, otherwise CO-RE relocation will 530 * fail. Custom user types are not relocatable with CO-RE. 531 * The typical situation in which BPF_CORE_READ_USER() might be used is to 532 * read kernel UAPI types from the user-space memory passed in as a syscall 533 * input argument. 534 */ 535 #define BPF_CORE_READ_USER(src, a, ...) ({ \ 536 ___type((src), a, ##__VA_ARGS__) __r; \ 537 BPF_CORE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \ 538 __r; \ 539 }) 540 541 /* Non-CO-RE variant of BPF_CORE_READ() */ 542 #define BPF_PROBE_READ(src, a, ...) ({ \ 543 ___type((src), a, ##__VA_ARGS__) __r; \ 544 BPF_PROBE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \ 545 __r; \ 546 }) 547 548 /* 549 * Non-CO-RE variant of BPF_CORE_READ_USER(). 550 * 551 * As no CO-RE relocations are emitted, source types can be arbitrary and are 552 * not restricted to kernel types only. 553 */ 554 #define BPF_PROBE_READ_USER(src, a, ...) ({ \ 555 ___type((src), a, ##__VA_ARGS__) __r; \ 556 BPF_PROBE_READ_USER_INTO(&__r, (src), a, ##__VA_ARGS__); \ 557 __r; \ 558 }) 559 560 #endif 561 562