1d7c4b398SAndrii Nakryiko /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ 2d7c4b398SAndrii Nakryiko 3d7c4b398SAndrii Nakryiko /* 4d7c4b398SAndrii Nakryiko * Internal libbpf helpers. 5d7c4b398SAndrii Nakryiko * 6d7c4b398SAndrii Nakryiko * Copyright (c) 2019 Facebook 7d7c4b398SAndrii Nakryiko */ 8d7c4b398SAndrii Nakryiko 9d7c4b398SAndrii Nakryiko #ifndef __LIBBPF_LIBBPF_INTERNAL_H 10d7c4b398SAndrii Nakryiko #define __LIBBPF_LIBBPF_INTERNAL_H 11d7c4b398SAndrii Nakryiko 12029258d7SAndrii Nakryiko #include <stdlib.h> 13dda1ec9fSAndrii Nakryiko #include <limits.h> 1485367030SAndrii Nakryiko 1585367030SAndrii Nakryiko /* make sure libbpf doesn't use kernel-only integer typedefs */ 1685367030SAndrii Nakryiko #pragma GCC poison u8 u16 u32 u64 s8 s16 s32 s64 1785367030SAndrii Nakryiko 1885367030SAndrii Nakryiko /* prevent accidental re-addition of reallocarray() */ 1985367030SAndrii Nakryiko #pragma GCC poison reallocarray 2085367030SAndrii Nakryiko 211d7a08b3SAndrii Nakryiko #include "libbpf.h" 221d7a08b3SAndrii Nakryiko 23d7c4b398SAndrii Nakryiko #define BTF_INFO_ENC(kind, kind_flag, vlen) \ 24d7c4b398SAndrii Nakryiko ((!!(kind_flag) << 31) | ((kind) << 24) | ((vlen) & BTF_MAX_VLEN)) 25d7c4b398SAndrii Nakryiko #define BTF_TYPE_ENC(name, info, size_or_type) (name), (info), (size_or_type) 26d7c4b398SAndrii Nakryiko #define BTF_INT_ENC(encoding, bits_offset, nr_bits) \ 27d7c4b398SAndrii Nakryiko ((encoding) << 24 | (bits_offset) << 16 | (nr_bits)) 28d7c4b398SAndrii Nakryiko #define BTF_TYPE_INT_ENC(name, encoding, bits_offset, bits, sz) \ 29d7c4b398SAndrii Nakryiko BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_INT, 0, 0), sz), \ 30d7c4b398SAndrii Nakryiko BTF_INT_ENC(encoding, bits_offset, bits) 31d7c4b398SAndrii Nakryiko #define BTF_MEMBER_ENC(name, type, bits_offset) (name), (type), (bits_offset) 32d7c4b398SAndrii Nakryiko #define BTF_PARAM_ENC(name, type) (name), (type) 33d7c4b398SAndrii Nakryiko #define BTF_VAR_SECINFO_ENC(type, offset, size) (type), (offset), (size) 34*22541a9eSIlya Leoshkevich #define BTF_TYPE_FLOAT_ENC(name, sz) \ 35*22541a9eSIlya Leoshkevich BTF_TYPE_ENC(name, BTF_INFO_ENC(BTF_KIND_FLOAT, 0, 0), sz) 36d7c4b398SAndrii Nakryiko 37029258d7SAndrii Nakryiko #ifndef likely 38029258d7SAndrii Nakryiko #define likely(x) __builtin_expect(!!(x), 1) 39029258d7SAndrii Nakryiko #endif 40029258d7SAndrii Nakryiko #ifndef unlikely 41029258d7SAndrii Nakryiko #define unlikely(x) __builtin_expect(!!(x), 0) 42029258d7SAndrii Nakryiko #endif 43d7fe74f9SAndrii Nakryiko #ifndef min 44d7fe74f9SAndrii Nakryiko # define min(x, y) ((x) < (y) ? (x) : (y)) 45d7fe74f9SAndrii Nakryiko #endif 46d7fe74f9SAndrii Nakryiko #ifndef max 47d7fe74f9SAndrii Nakryiko # define max(x, y) ((x) < (y) ? (y) : (x)) 48d7fe74f9SAndrii Nakryiko #endif 494cedc0daSAndrii Nakryiko #ifndef offsetofend 504cedc0daSAndrii Nakryiko # define offsetofend(TYPE, FIELD) \ 514cedc0daSAndrii Nakryiko (offsetof(TYPE, FIELD) + sizeof(((TYPE *)0)->FIELD)) 524cedc0daSAndrii Nakryiko #endif 53d7fe74f9SAndrii Nakryiko 541bd63524SYonghong Song /* Symbol versioning is different between static and shared library. 551bd63524SYonghong Song * Properly versioned symbols are needed for shared library, but 561bd63524SYonghong Song * only the symbol of the new version is needed for static library. 571bd63524SYonghong Song */ 581bd63524SYonghong Song #ifdef SHARED 591bd63524SYonghong Song # define COMPAT_VERSION(internal_name, api_name, version) \ 601bd63524SYonghong Song asm(".symver " #internal_name "," #api_name "@" #version); 611bd63524SYonghong Song # define DEFAULT_VERSION(internal_name, api_name, version) \ 621bd63524SYonghong Song asm(".symver " #internal_name "," #api_name "@@" #version); 631bd63524SYonghong Song #else 641bd63524SYonghong Song # define COMPAT_VERSION(internal_name, api_name, version) 651bd63524SYonghong Song # define DEFAULT_VERSION(internal_name, api_name, version) \ 661bd63524SYonghong Song extern typeof(internal_name) api_name \ 671bd63524SYonghong Song __attribute__((alias(#internal_name))); 681bd63524SYonghong Song #endif 691bd63524SYonghong Song 70d72386feSAndrii Nakryiko extern void libbpf_print(enum libbpf_print_level level, 71d72386feSAndrii Nakryiko const char *format, ...) 72d72386feSAndrii Nakryiko __attribute__((format(printf, 2, 3))); 73d72386feSAndrii Nakryiko 74d72386feSAndrii Nakryiko #define __pr(level, fmt, ...) \ 75d72386feSAndrii Nakryiko do { \ 76d72386feSAndrii Nakryiko libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__); \ 77d72386feSAndrii Nakryiko } while (0) 78d72386feSAndrii Nakryiko 79be18010eSKefeng Wang #define pr_warn(fmt, ...) __pr(LIBBPF_WARN, fmt, ##__VA_ARGS__) 80d72386feSAndrii Nakryiko #define pr_info(fmt, ...) __pr(LIBBPF_INFO, fmt, ##__VA_ARGS__) 81d72386feSAndrii Nakryiko #define pr_debug(fmt, ...) __pr(LIBBPF_DEBUG, fmt, ##__VA_ARGS__) 82d72386feSAndrii Nakryiko 83dda1ec9fSAndrii Nakryiko #ifndef __has_builtin 84dda1ec9fSAndrii Nakryiko #define __has_builtin(x) 0 85dda1ec9fSAndrii Nakryiko #endif 86029258d7SAndrii Nakryiko /* 87029258d7SAndrii Nakryiko * Re-implement glibc's reallocarray() for libbpf internal-only use. 88029258d7SAndrii Nakryiko * reallocarray(), unfortunately, is not available in all versions of glibc, 89029258d7SAndrii Nakryiko * so requires extra feature detection and using reallocarray() stub from 90029258d7SAndrii Nakryiko * <tools/libc_compat.h> and COMPAT_NEED_REALLOCARRAY. All this complicates 91029258d7SAndrii Nakryiko * build of libbpf unnecessarily and is just a maintenance burden. Instead, 92029258d7SAndrii Nakryiko * it's trivial to implement libbpf-specific internal version and use it 93029258d7SAndrii Nakryiko * throughout libbpf. 94029258d7SAndrii Nakryiko */ 95029258d7SAndrii Nakryiko static inline void *libbpf_reallocarray(void *ptr, size_t nmemb, size_t size) 96029258d7SAndrii Nakryiko { 97029258d7SAndrii Nakryiko size_t total; 98029258d7SAndrii Nakryiko 99dda1ec9fSAndrii Nakryiko #if __has_builtin(__builtin_mul_overflow) 100029258d7SAndrii Nakryiko if (unlikely(__builtin_mul_overflow(nmemb, size, &total))) 101029258d7SAndrii Nakryiko return NULL; 102dda1ec9fSAndrii Nakryiko #else 103dda1ec9fSAndrii Nakryiko if (size == 0 || nmemb > ULONG_MAX / size) 104dda1ec9fSAndrii Nakryiko return NULL; 105dda1ec9fSAndrii Nakryiko total = nmemb * size; 106dda1ec9fSAndrii Nakryiko #endif 107029258d7SAndrii Nakryiko return realloc(ptr, total); 108029258d7SAndrii Nakryiko } 109029258d7SAndrii Nakryiko 110192f5a1fSAndrii Nakryiko void *btf_add_mem(void **data, size_t *cap_cnt, size_t elem_sz, 111192f5a1fSAndrii Nakryiko size_t cur_cnt, size_t max_cnt, size_t add_cnt); 1129c6c5c48SAndrii Nakryiko int btf_ensure_mem(void **data, size_t *cap_cnt, size_t elem_sz, size_t need_cnt); 113192f5a1fSAndrii Nakryiko 1142ce8450eSAndrii Nakryiko static inline bool libbpf_validate_opts(const char *opts, 1152ce8450eSAndrii Nakryiko size_t opts_sz, size_t user_sz, 1162ce8450eSAndrii Nakryiko const char *type_name) 1172ce8450eSAndrii Nakryiko { 1182ce8450eSAndrii Nakryiko if (user_sz < sizeof(size_t)) { 119be18010eSKefeng Wang pr_warn("%s size (%zu) is too small\n", type_name, user_sz); 1202ce8450eSAndrii Nakryiko return false; 1212ce8450eSAndrii Nakryiko } 1222ce8450eSAndrii Nakryiko if (user_sz > opts_sz) { 1232ce8450eSAndrii Nakryiko size_t i; 1242ce8450eSAndrii Nakryiko 1252ce8450eSAndrii Nakryiko for (i = opts_sz; i < user_sz; i++) { 1262ce8450eSAndrii Nakryiko if (opts[i]) { 12712dd14b2SToke Høiland-Jørgensen pr_warn("%s has non-zero extra bytes\n", 1282ce8450eSAndrii Nakryiko type_name); 1292ce8450eSAndrii Nakryiko return false; 1302ce8450eSAndrii Nakryiko } 1312ce8450eSAndrii Nakryiko } 1322ce8450eSAndrii Nakryiko } 1332ce8450eSAndrii Nakryiko return true; 1342ce8450eSAndrii Nakryiko } 1352ce8450eSAndrii Nakryiko 1362ce8450eSAndrii Nakryiko #define OPTS_VALID(opts, type) \ 1372ce8450eSAndrii Nakryiko (!(opts) || libbpf_validate_opts((const char *)opts, \ 1382ce8450eSAndrii Nakryiko offsetofend(struct type, \ 1392ce8450eSAndrii Nakryiko type##__last_field), \ 1402ce8450eSAndrii Nakryiko (opts)->sz, #type)) 1412ce8450eSAndrii Nakryiko #define OPTS_HAS(opts, field) \ 1422ce8450eSAndrii Nakryiko ((opts) && opts->sz >= offsetofend(typeof(*(opts)), field)) 1432ce8450eSAndrii Nakryiko #define OPTS_GET(opts, field, fallback_value) \ 1442ce8450eSAndrii Nakryiko (OPTS_HAS(opts, field) ? (opts)->field : fallback_value) 14588f7fe72SSong Liu #define OPTS_SET(opts, field, value) \ 14688f7fe72SSong Liu do { \ 14788f7fe72SSong Liu if (OPTS_HAS(opts, field)) \ 14888f7fe72SSong Liu (opts)->field = value; \ 14988f7fe72SSong Liu } while (0) 1502ce8450eSAndrii Nakryiko 1516803ee25SAndrii Nakryiko int parse_cpu_mask_str(const char *s, bool **mask, int *mask_sz); 1526803ee25SAndrii Nakryiko int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz); 153cfd49210SMichal Rostecki int libbpf__load_raw_btf(const char *raw_types, size_t types_len, 154d7c4b398SAndrii Nakryiko const char *str_sec, size_t str_len); 155d7c4b398SAndrii Nakryiko 1566aef10a4SAndrii Nakryiko struct bpf_prog_load_params { 1576aef10a4SAndrii Nakryiko enum bpf_prog_type prog_type; 1586aef10a4SAndrii Nakryiko enum bpf_attach_type expected_attach_type; 1596aef10a4SAndrii Nakryiko const char *name; 1606aef10a4SAndrii Nakryiko const struct bpf_insn *insns; 1616aef10a4SAndrii Nakryiko size_t insn_cnt; 1626aef10a4SAndrii Nakryiko const char *license; 1636aef10a4SAndrii Nakryiko __u32 kern_version; 1646aef10a4SAndrii Nakryiko __u32 attach_prog_fd; 16591abb4a6SAndrii Nakryiko __u32 attach_btf_obj_fd; 1666aef10a4SAndrii Nakryiko __u32 attach_btf_id; 1676aef10a4SAndrii Nakryiko __u32 prog_ifindex; 1686aef10a4SAndrii Nakryiko __u32 prog_btf_fd; 1696aef10a4SAndrii Nakryiko __u32 prog_flags; 1706aef10a4SAndrii Nakryiko 1716aef10a4SAndrii Nakryiko __u32 func_info_rec_size; 1726aef10a4SAndrii Nakryiko const void *func_info; 1736aef10a4SAndrii Nakryiko __u32 func_info_cnt; 1746aef10a4SAndrii Nakryiko 1756aef10a4SAndrii Nakryiko __u32 line_info_rec_size; 1766aef10a4SAndrii Nakryiko const void *line_info; 1776aef10a4SAndrii Nakryiko __u32 line_info_cnt; 1786aef10a4SAndrii Nakryiko 1796aef10a4SAndrii Nakryiko __u32 log_level; 1806aef10a4SAndrii Nakryiko char *log_buf; 1816aef10a4SAndrii Nakryiko size_t log_buf_sz; 1826aef10a4SAndrii Nakryiko }; 1836aef10a4SAndrii Nakryiko 1846aef10a4SAndrii Nakryiko int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr); 1856aef10a4SAndrii Nakryiko 186612d05beSAndrii Nakryiko int bpf_object__section_size(const struct bpf_object *obj, const char *name, 187612d05beSAndrii Nakryiko __u32 *size); 188612d05beSAndrii Nakryiko int bpf_object__variable_offset(const struct bpf_object *obj, const char *name, 189612d05beSAndrii Nakryiko __u32 *off); 190a19f93cfSAndrii Nakryiko struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf); 191612d05beSAndrii Nakryiko 1924cedc0daSAndrii Nakryiko struct btf_ext_info { 1934cedc0daSAndrii Nakryiko /* 1944cedc0daSAndrii Nakryiko * info points to the individual info section (e.g. func_info and 1954cedc0daSAndrii Nakryiko * line_info) from the .BTF.ext. It does not include the __u32 rec_size. 1964cedc0daSAndrii Nakryiko */ 1974cedc0daSAndrii Nakryiko void *info; 1984cedc0daSAndrii Nakryiko __u32 rec_size; 1994cedc0daSAndrii Nakryiko __u32 len; 2004cedc0daSAndrii Nakryiko }; 2014cedc0daSAndrii Nakryiko 2024cedc0daSAndrii Nakryiko #define for_each_btf_ext_sec(seg, sec) \ 2034cedc0daSAndrii Nakryiko for (sec = (seg)->info; \ 2044cedc0daSAndrii Nakryiko (void *)sec < (seg)->info + (seg)->len; \ 2054cedc0daSAndrii Nakryiko sec = (void *)sec + sizeof(struct btf_ext_info_sec) + \ 2064cedc0daSAndrii Nakryiko (seg)->rec_size * sec->num_info) 2074cedc0daSAndrii Nakryiko 2084cedc0daSAndrii Nakryiko #define for_each_btf_ext_rec(seg, sec, i, rec) \ 2094cedc0daSAndrii Nakryiko for (i = 0, rec = (void *)&(sec)->data; \ 2104cedc0daSAndrii Nakryiko i < (sec)->num_info; \ 2114cedc0daSAndrii Nakryiko i++, rec = (void *)rec + (seg)->rec_size) 2124cedc0daSAndrii Nakryiko 21328b93c64SAndrii Nakryiko /* 21428b93c64SAndrii Nakryiko * The .BTF.ext ELF section layout defined as 21528b93c64SAndrii Nakryiko * struct btf_ext_header 21628b93c64SAndrii Nakryiko * func_info subsection 21728b93c64SAndrii Nakryiko * 21828b93c64SAndrii Nakryiko * The func_info subsection layout: 21928b93c64SAndrii Nakryiko * record size for struct bpf_func_info in the func_info subsection 22028b93c64SAndrii Nakryiko * struct btf_sec_func_info for section #1 22128b93c64SAndrii Nakryiko * a list of bpf_func_info records for section #1 22228b93c64SAndrii Nakryiko * where struct bpf_func_info mimics one in include/uapi/linux/bpf.h 22328b93c64SAndrii Nakryiko * but may not be identical 22428b93c64SAndrii Nakryiko * struct btf_sec_func_info for section #2 22528b93c64SAndrii Nakryiko * a list of bpf_func_info records for section #2 22628b93c64SAndrii Nakryiko * ...... 22728b93c64SAndrii Nakryiko * 22828b93c64SAndrii Nakryiko * Note that the bpf_func_info record size in .BTF.ext may not 22928b93c64SAndrii Nakryiko * be the same as the one defined in include/uapi/linux/bpf.h. 23028b93c64SAndrii Nakryiko * The loader should ensure that record_size meets minimum 23128b93c64SAndrii Nakryiko * requirement and pass the record as is to the kernel. The 23228b93c64SAndrii Nakryiko * kernel will handle the func_info properly based on its contents. 23328b93c64SAndrii Nakryiko */ 23428b93c64SAndrii Nakryiko struct btf_ext_header { 23528b93c64SAndrii Nakryiko __u16 magic; 23628b93c64SAndrii Nakryiko __u8 version; 23728b93c64SAndrii Nakryiko __u8 flags; 23828b93c64SAndrii Nakryiko __u32 hdr_len; 23928b93c64SAndrii Nakryiko 24028b93c64SAndrii Nakryiko /* All offsets are in bytes relative to the end of this header */ 24128b93c64SAndrii Nakryiko __u32 func_info_off; 24228b93c64SAndrii Nakryiko __u32 func_info_len; 24328b93c64SAndrii Nakryiko __u32 line_info_off; 24428b93c64SAndrii Nakryiko __u32 line_info_len; 24528b93c64SAndrii Nakryiko 24628b93c64SAndrii Nakryiko /* optional part of .BTF.ext header */ 24728b93c64SAndrii Nakryiko __u32 core_relo_off; 24828b93c64SAndrii Nakryiko __u32 core_relo_len; 24928b93c64SAndrii Nakryiko }; 25028b93c64SAndrii Nakryiko 2514cedc0daSAndrii Nakryiko struct btf_ext { 2524cedc0daSAndrii Nakryiko union { 2534cedc0daSAndrii Nakryiko struct btf_ext_header *hdr; 2544cedc0daSAndrii Nakryiko void *data; 2554cedc0daSAndrii Nakryiko }; 2564cedc0daSAndrii Nakryiko struct btf_ext_info func_info; 2574cedc0daSAndrii Nakryiko struct btf_ext_info line_info; 25828b93c64SAndrii Nakryiko struct btf_ext_info core_relo_info; 2594cedc0daSAndrii Nakryiko __u32 data_size; 2604cedc0daSAndrii Nakryiko }; 2614cedc0daSAndrii Nakryiko 2624cedc0daSAndrii Nakryiko struct btf_ext_info_sec { 2634cedc0daSAndrii Nakryiko __u32 sec_name_off; 2644cedc0daSAndrii Nakryiko __u32 num_info; 2654cedc0daSAndrii Nakryiko /* Followed by num_info * record_size number of bytes */ 266385bbf7bSGustavo A. R. Silva __u8 data[]; 2674cedc0daSAndrii Nakryiko }; 2684cedc0daSAndrii Nakryiko 2694cedc0daSAndrii Nakryiko /* The minimum bpf_func_info checked by the loader */ 2704cedc0daSAndrii Nakryiko struct bpf_func_info_min { 2714cedc0daSAndrii Nakryiko __u32 insn_off; 2724cedc0daSAndrii Nakryiko __u32 type_id; 2734cedc0daSAndrii Nakryiko }; 2744cedc0daSAndrii Nakryiko 2754cedc0daSAndrii Nakryiko /* The minimum bpf_line_info checked by the loader */ 2764cedc0daSAndrii Nakryiko struct bpf_line_info_min { 2774cedc0daSAndrii Nakryiko __u32 insn_off; 2784cedc0daSAndrii Nakryiko __u32 file_name_off; 2794cedc0daSAndrii Nakryiko __u32 line_off; 2804cedc0daSAndrii Nakryiko __u32 line_col; 2814cedc0daSAndrii Nakryiko }; 2824cedc0daSAndrii Nakryiko 28328b93c64SAndrii Nakryiko /* bpf_core_relo_kind encodes which aspect of captured field/type/enum value 28428b93c64SAndrii Nakryiko * has to be adjusted by relocations. 285511bb008SAndrii Nakryiko */ 28628b93c64SAndrii Nakryiko enum bpf_core_relo_kind { 287511bb008SAndrii Nakryiko BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */ 28828b93c64SAndrii Nakryiko BPF_FIELD_BYTE_SIZE = 1, /* field size in bytes */ 289511bb008SAndrii Nakryiko BPF_FIELD_EXISTS = 2, /* field existence in target kernel */ 29028b93c64SAndrii Nakryiko BPF_FIELD_SIGNED = 3, /* field signedness (0 - unsigned, 1 - signed) */ 29128b93c64SAndrii Nakryiko BPF_FIELD_LSHIFT_U64 = 4, /* bitfield-specific left bitshift */ 29228b93c64SAndrii Nakryiko BPF_FIELD_RSHIFT_U64 = 5, /* bitfield-specific right bitshift */ 2933fc32f40SAndrii Nakryiko BPF_TYPE_ID_LOCAL = 6, /* type ID in local BPF object */ 2943fc32f40SAndrii Nakryiko BPF_TYPE_ID_TARGET = 7, /* type ID in target kernel */ 2953fc32f40SAndrii Nakryiko BPF_TYPE_EXISTS = 8, /* type existence in target kernel */ 2963fc32f40SAndrii Nakryiko BPF_TYPE_SIZE = 9, /* type size in bytes */ 297eacaaed7SAndrii Nakryiko BPF_ENUMVAL_EXISTS = 10, /* enum value existence in target kernel */ 298eacaaed7SAndrii Nakryiko BPF_ENUMVAL_VALUE = 11, /* enum value integer value */ 299511bb008SAndrii Nakryiko }; 300511bb008SAndrii Nakryiko 30128b93c64SAndrii Nakryiko /* The minimum bpf_core_relo checked by the loader 3024cedc0daSAndrii Nakryiko * 30328b93c64SAndrii Nakryiko * CO-RE relocation captures the following data: 3044cedc0daSAndrii Nakryiko * - insn_off - instruction offset (in bytes) within a BPF program that needs 305511bb008SAndrii Nakryiko * its insn->imm field to be relocated with actual field info; 3064cedc0daSAndrii Nakryiko * - type_id - BTF type ID of the "root" (containing) entity of a relocatable 30728b93c64SAndrii Nakryiko * type or field; 3084cedc0daSAndrii Nakryiko * - access_str_off - offset into corresponding .BTF string section. String 30928b93c64SAndrii Nakryiko * interpretation depends on specific relocation kind: 31028b93c64SAndrii Nakryiko * - for field-based relocations, string encodes an accessed field using 31128b93c64SAndrii Nakryiko * a sequence of field and array indices, separated by colon (:). It's 31228b93c64SAndrii Nakryiko * conceptually very close to LLVM's getelementptr ([0]) instruction's 31328b93c64SAndrii Nakryiko * arguments for identifying offset to a field. 31428b93c64SAndrii Nakryiko * - for type-based relocations, strings is expected to be just "0"; 31528b93c64SAndrii Nakryiko * - for enum value-based relocations, string contains an index of enum 31628b93c64SAndrii Nakryiko * value within its enum type; 3174cedc0daSAndrii Nakryiko * 3184cedc0daSAndrii Nakryiko * Example to provide a better feel. 3194cedc0daSAndrii Nakryiko * 3204cedc0daSAndrii Nakryiko * struct sample { 3214cedc0daSAndrii Nakryiko * int a; 3224cedc0daSAndrii Nakryiko * struct { 3234cedc0daSAndrii Nakryiko * int b[10]; 3244cedc0daSAndrii Nakryiko * }; 3254cedc0daSAndrii Nakryiko * }; 3264cedc0daSAndrii Nakryiko * 3274cedc0daSAndrii Nakryiko * struct sample *s = ...; 3284cedc0daSAndrii Nakryiko * int x = &s->a; // encoded as "0:0" (a is field #0) 3294cedc0daSAndrii Nakryiko * int y = &s->b[5]; // encoded as "0:1:0:5" (anon struct is field #1, 3304cedc0daSAndrii Nakryiko * // b is field #0 inside anon struct, accessing elem #5) 3314cedc0daSAndrii Nakryiko * int z = &s[10]->b; // encoded as "10:1" (ptr is used as an array) 3324cedc0daSAndrii Nakryiko * 3334cedc0daSAndrii Nakryiko * type_id for all relocs in this example will capture BTF type id of 3344cedc0daSAndrii Nakryiko * `struct sample`. 3354cedc0daSAndrii Nakryiko * 3364cedc0daSAndrii Nakryiko * Such relocation is emitted when using __builtin_preserve_access_index() 3374cedc0daSAndrii Nakryiko * Clang built-in, passing expression that captures field address, e.g.: 3384cedc0daSAndrii Nakryiko * 3394cedc0daSAndrii Nakryiko * bpf_probe_read(&dst, sizeof(dst), 3404cedc0daSAndrii Nakryiko * __builtin_preserve_access_index(&src->a.b.c)); 3414cedc0daSAndrii Nakryiko * 342511bb008SAndrii Nakryiko * In this case Clang will emit field relocation recording necessary data to 3434cedc0daSAndrii Nakryiko * be able to find offset of embedded `a.b.c` field within `src` struct. 3444cedc0daSAndrii Nakryiko * 3454cedc0daSAndrii Nakryiko * [0] https://llvm.org/docs/LangRef.html#getelementptr-instruction 3464cedc0daSAndrii Nakryiko */ 34728b93c64SAndrii Nakryiko struct bpf_core_relo { 3484cedc0daSAndrii Nakryiko __u32 insn_off; 3494cedc0daSAndrii Nakryiko __u32 type_id; 3504cedc0daSAndrii Nakryiko __u32 access_str_off; 35128b93c64SAndrii Nakryiko enum bpf_core_relo_kind kind; 3524cedc0daSAndrii Nakryiko }; 3534cedc0daSAndrii Nakryiko 354d7c4b398SAndrii Nakryiko #endif /* __LIBBPF_LIBBPF_INTERNAL_H */ 355