| /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ |
| #ifndef __BPF_CORE_READ_H__ |
| #define __BPF_CORE_READ_H__ |
| |
| /* |
| * enum bpf_field_info_kind is passed as a second argument into |
| * __builtin_preserve_field_info() built-in to get a specific aspect of |
| * a field, captured as a first argument. __builtin_preserve_field_info(field, |
| * info_kind) returns __u32 integer and produces BTF field relocation, which |
| * is understood and processed by libbpf during BPF object loading. See |
| * selftests/bpf for examples. |
| */ |
| enum bpf_field_info_kind { |
| BPF_FIELD_BYTE_OFFSET = 0, /* field byte offset */ |
| BPF_FIELD_BYTE_SIZE = 1, |
| BPF_FIELD_EXISTS = 2, /* field existence in target kernel */ |
| BPF_FIELD_SIGNED = 3, |
| BPF_FIELD_LSHIFT_U64 = 4, |
| BPF_FIELD_RSHIFT_U64 = 5, |
| }; |
| |
| #define __CORE_RELO(src, field, info) \ |
| __builtin_preserve_field_info((src)->field, BPF_FIELD_##info) |
| |
| #if __BYTE_ORDER == __LITTLE_ENDIAN |
| #define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \ |
| bpf_probe_read((void *)dst, \ |
| __CORE_RELO(src, fld, BYTE_SIZE), \ |
| (const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET)) |
| #else |
| /* semantics of LSHIFT_64 assumes loading values into low-ordered bytes, so |
| * for big-endian we need to adjust destination pointer accordingly, based on |
| * field byte size |
| */ |
| #define __CORE_BITFIELD_PROBE_READ(dst, src, fld) \ |
| bpf_probe_read((void *)dst + (8 - __CORE_RELO(src, fld, BYTE_SIZE)), \ |
| __CORE_RELO(src, fld, BYTE_SIZE), \ |
| (const void *)src + __CORE_RELO(src, fld, BYTE_OFFSET)) |
| #endif |
| |
| /* |
| * Extract bitfield, identified by s->field, and return its value as u64. |
| * All this is done in relocatable manner, so bitfield changes such as |
| * signedness, bit size, offset changes, this will be handled automatically. |
| * This version of macro is using bpf_probe_read() to read underlying integer |
| * storage. Macro functions as an expression and its return type is |
| * bpf_probe_read()'s return value: 0, on success, <0 on error. |
| */ |
| #define BPF_CORE_READ_BITFIELD_PROBED(s, field) ({ \ |
| unsigned long long val = 0; \ |
| \ |
| __CORE_BITFIELD_PROBE_READ(&val, s, field); \ |
| val <<= __CORE_RELO(s, field, LSHIFT_U64); \ |
| if (__CORE_RELO(s, field, SIGNED)) \ |
| val = ((long long)val) >> __CORE_RELO(s, field, RSHIFT_U64); \ |
| else \ |
| val = val >> __CORE_RELO(s, field, RSHIFT_U64); \ |
| val; \ |
| }) |
| |
| /* |
| * Extract bitfield, identified by s->field, and return its value as u64. |
| * This version of macro is using direct memory reads and should be used from |
| * BPF program types that support such functionality (e.g., typed raw |
| * tracepoints). |
| */ |
| #define BPF_CORE_READ_BITFIELD(s, field) ({ \ |
| const void *p = (const void *)s + __CORE_RELO(s, field, BYTE_OFFSET); \ |
| unsigned long long val; \ |
| \ |
| switch (__CORE_RELO(s, field, BYTE_SIZE)) { \ |
| case 1: val = *(const unsigned char *)p; \ |
| case 2: val = *(const unsigned short *)p; \ |
| case 4: val = *(const unsigned int *)p; \ |
| case 8: val = *(const unsigned long long *)p; \ |
| } \ |
| val <<= __CORE_RELO(s, field, LSHIFT_U64); \ |
| if (__CORE_RELO(s, field, SIGNED)) \ |
| val = ((long long)val) >> __CORE_RELO(s, field, RSHIFT_U64); \ |
| else \ |
| val = val >> __CORE_RELO(s, field, RSHIFT_U64); \ |
| val; \ |
| }) |
| |
| /* |
| * Convenience macro to check that field actually exists in target kernel's. |
| * Returns: |
| * 1, if matching field is present in target kernel; |
| * 0, if no matching field found. |
| */ |
| #define bpf_core_field_exists(field) \ |
| __builtin_preserve_field_info(field, BPF_FIELD_EXISTS) |
| |
| /* |
| * Convenience macro to get byte size of a field. Works for integers, |
| * struct/unions, pointers, arrays, and enums. |
| */ |
| #define bpf_core_field_size(field) \ |
| __builtin_preserve_field_info(field, BPF_FIELD_BYTE_SIZE) |
| |
| /* |
| * bpf_core_read() abstracts away bpf_probe_read() call and captures offset |
| * relocation for source address using __builtin_preserve_access_index() |
| * built-in, provided by Clang. |
| * |
| * __builtin_preserve_access_index() takes as an argument an expression of |
| * taking an address of a field within struct/union. It makes compiler emit |
| * a relocation, which records BTF type ID describing root struct/union and an |
| * accessor string which describes exact embedded field that was used to take |
| * an address. See detailed description of this relocation format and |
| * semantics in comments to struct bpf_field_reloc in libbpf_internal.h. |
| * |
| * This relocation allows libbpf to adjust BPF instruction to use correct |
| * actual field offset, based on target kernel BTF type that matches original |
| * (local) BTF, used to record relocation. |
| */ |
| #define bpf_core_read(dst, sz, src) \ |
| bpf_probe_read(dst, sz, \ |
| (const void *)__builtin_preserve_access_index(src)) |
| |
| /* |
| * bpf_core_read_str() is a thin wrapper around bpf_probe_read_str() |
| * additionally emitting BPF CO-RE field relocation for specified source |
| * argument. |
| */ |
| #define bpf_core_read_str(dst, sz, src) \ |
| bpf_probe_read_str(dst, sz, \ |
| (const void *)__builtin_preserve_access_index(src)) |
| |
| #define ___concat(a, b) a ## b |
| #define ___apply(fn, n) ___concat(fn, n) |
| #define ___nth(_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, __11, N, ...) N |
| |
| /* |
| * return number of provided arguments; used for switch-based variadic macro |
| * definitions (see ___last, ___arrow, etc below) |
| */ |
| #define ___narg(...) ___nth(_, ##__VA_ARGS__, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) |
| /* |
| * return 0 if no arguments are passed, N - otherwise; used for |
| * recursively-defined macros to specify termination (0) case, and generic |
| * (N) case (e.g., ___read_ptrs, ___core_read) |
| */ |
| #define ___empty(...) ___nth(_, ##__VA_ARGS__, N, N, N, N, N, N, N, N, N, N, 0) |
| |
| #define ___last1(x) x |
| #define ___last2(a, x) x |
| #define ___last3(a, b, x) x |
| #define ___last4(a, b, c, x) x |
| #define ___last5(a, b, c, d, x) x |
| #define ___last6(a, b, c, d, e, x) x |
| #define ___last7(a, b, c, d, e, f, x) x |
| #define ___last8(a, b, c, d, e, f, g, x) x |
| #define ___last9(a, b, c, d, e, f, g, h, x) x |
| #define ___last10(a, b, c, d, e, f, g, h, i, x) x |
| #define ___last(...) ___apply(___last, ___narg(__VA_ARGS__))(__VA_ARGS__) |
| |
| #define ___nolast2(a, _) a |
| #define ___nolast3(a, b, _) a, b |
| #define ___nolast4(a, b, c, _) a, b, c |
| #define ___nolast5(a, b, c, d, _) a, b, c, d |
| #define ___nolast6(a, b, c, d, e, _) a, b, c, d, e |
| #define ___nolast7(a, b, c, d, e, f, _) a, b, c, d, e, f |
| #define ___nolast8(a, b, c, d, e, f, g, _) a, b, c, d, e, f, g |
| #define ___nolast9(a, b, c, d, e, f, g, h, _) a, b, c, d, e, f, g, h |
| #define ___nolast10(a, b, c, d, e, f, g, h, i, _) a, b, c, d, e, f, g, h, i |
| #define ___nolast(...) ___apply(___nolast, ___narg(__VA_ARGS__))(__VA_ARGS__) |
| |
| #define ___arrow1(a) a |
| #define ___arrow2(a, b) a->b |
| #define ___arrow3(a, b, c) a->b->c |
| #define ___arrow4(a, b, c, d) a->b->c->d |
| #define ___arrow5(a, b, c, d, e) a->b->c->d->e |
| #define ___arrow6(a, b, c, d, e, f) a->b->c->d->e->f |
| #define ___arrow7(a, b, c, d, e, f, g) a->b->c->d->e->f->g |
| #define ___arrow8(a, b, c, d, e, f, g, h) a->b->c->d->e->f->g->h |
| #define ___arrow9(a, b, c, d, e, f, g, h, i) a->b->c->d->e->f->g->h->i |
| #define ___arrow10(a, b, c, d, e, f, g, h, i, j) a->b->c->d->e->f->g->h->i->j |
| #define ___arrow(...) ___apply(___arrow, ___narg(__VA_ARGS__))(__VA_ARGS__) |
| |
| #define ___type(...) typeof(___arrow(__VA_ARGS__)) |
| |
| #define ___read(read_fn, dst, src_type, src, accessor) \ |
| read_fn((void *)(dst), sizeof(*(dst)), &((src_type)(src))->accessor) |
| |
| /* "recursively" read a sequence of inner pointers using local __t var */ |
| #define ___rd_first(src, a) ___read(bpf_core_read, &__t, ___type(src), src, a); |
| #define ___rd_last(...) \ |
| ___read(bpf_core_read, &__t, \ |
| ___type(___nolast(__VA_ARGS__)), __t, ___last(__VA_ARGS__)); |
| #define ___rd_p1(...) const void *__t; ___rd_first(__VA_ARGS__) |
| #define ___rd_p2(...) ___rd_p1(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___rd_p3(...) ___rd_p2(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___rd_p4(...) ___rd_p3(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___rd_p5(...) ___rd_p4(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___rd_p6(...) ___rd_p5(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___rd_p7(...) ___rd_p6(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___rd_p8(...) ___rd_p7(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___rd_p9(...) ___rd_p8(___nolast(__VA_ARGS__)) ___rd_last(__VA_ARGS__) |
| #define ___read_ptrs(src, ...) \ |
| ___apply(___rd_p, ___narg(__VA_ARGS__))(src, __VA_ARGS__) |
| |
| #define ___core_read0(fn, dst, src, a) \ |
| ___read(fn, dst, ___type(src), src, a); |
| #define ___core_readN(fn, dst, src, ...) \ |
| ___read_ptrs(src, ___nolast(__VA_ARGS__)) \ |
| ___read(fn, dst, ___type(src, ___nolast(__VA_ARGS__)), __t, \ |
| ___last(__VA_ARGS__)); |
| #define ___core_read(fn, dst, src, a, ...) \ |
| ___apply(___core_read, ___empty(__VA_ARGS__))(fn, dst, \ |
| src, a, ##__VA_ARGS__) |
| |
| /* |
| * BPF_CORE_READ_INTO() is a more performance-conscious variant of |
| * BPF_CORE_READ(), in which final field is read into user-provided storage. |
| * See BPF_CORE_READ() below for more details on general usage. |
| */ |
| #define BPF_CORE_READ_INTO(dst, src, a, ...) \ |
| ({ \ |
| ___core_read(bpf_core_read, dst, (src), a, ##__VA_ARGS__) \ |
| }) |
| |
| /* |
| * BPF_CORE_READ_STR_INTO() does same "pointer chasing" as |
| * BPF_CORE_READ() for intermediate pointers, but then executes (and returns |
| * corresponding error code) bpf_core_read_str() for final string read. |
| */ |
| #define BPF_CORE_READ_STR_INTO(dst, src, a, ...) \ |
| ({ \ |
| ___core_read(bpf_core_read_str, dst, (src), a, ##__VA_ARGS__)\ |
| }) |
| |
| /* |
| * BPF_CORE_READ() is used to simplify BPF CO-RE relocatable read, especially |
| * when there are few pointer chasing steps. |
| * E.g., what in non-BPF world (or in BPF w/ BCC) would be something like: |
| * int x = s->a.b.c->d.e->f->g; |
| * can be succinctly achieved using BPF_CORE_READ as: |
| * int x = BPF_CORE_READ(s, a.b.c, d.e, f, g); |
| * |
| * BPF_CORE_READ will decompose above statement into 4 bpf_core_read (BPF |
| * CO-RE relocatable bpf_probe_read() wrapper) calls, logically equivalent to: |
| * 1. const void *__t = s->a.b.c; |
| * 2. __t = __t->d.e; |
| * 3. __t = __t->f; |
| * 4. return __t->g; |
| * |
| * Equivalence is logical, because there is a heavy type casting/preservation |
| * involved, as well as all the reads are happening through bpf_probe_read() |
| * calls using __builtin_preserve_access_index() to emit CO-RE relocations. |
| * |
| * N.B. Only up to 9 "field accessors" are supported, which should be more |
| * than enough for any practical purpose. |
| */ |
| #define BPF_CORE_READ(src, a, ...) \ |
| ({ \ |
| ___type((src), a, ##__VA_ARGS__) __r; \ |
| BPF_CORE_READ_INTO(&__r, (src), a, ##__VA_ARGS__); \ |
| __r; \ |
| }) |
| |
| #endif |
| |