1 /* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ 2 #ifndef __BPF_HELPERS__ 3 #define __BPF_HELPERS__ 4 5 /* 6 * Note that bpf programs need to include either 7 * vmlinux.h (auto-generated from BTF) or linux/types.h 8 * in advance since bpf_helper_defs.h uses such types 9 * as __u64. 10 */ 11 #include "bpf_helper_defs.h" 12 13 #define __uint(name, val) int (*name)[val] 14 #define __type(name, val) typeof(val) *name 15 #define __array(name, val) typeof(val) *name[] 16 #define __ulong(name, val) enum { ___bpf_concat(__unique_value, __COUNTER__) = val } name 17 18 /* 19 * Helper macro to place programs, maps, license in 20 * different sections in elf_bpf file. Section names 21 * are interpreted by libbpf depending on the context (BPF programs, BPF maps, 22 * extern variables, etc). 23 * To allow use of SEC() with externs (e.g., for extern .maps declarations), 24 * make sure __attribute__((unused)) doesn't trigger compilation warning. 25 */ 26 #if __GNUC__ && !__clang__ 27 28 /* 29 * Pragma macros are broken on GCC 30 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55578 31 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90400 32 */ 33 #define SEC(name) __attribute__((section(name), used)) 34 35 #else 36 37 #define SEC(name) \ 38 _Pragma("GCC diagnostic push") \ 39 _Pragma("GCC diagnostic ignored \"-Wignored-attributes\"") \ 40 __attribute__((section(name), used)) \ 41 _Pragma("GCC diagnostic pop") \ 42 43 #endif 44 45 /* Avoid 'linux/stddef.h' definition of '__always_inline'. */ 46 #undef __always_inline 47 #define __always_inline inline __attribute__((always_inline)) 48 49 #ifndef __noinline 50 #define __noinline __attribute__((noinline)) 51 #endif 52 #ifndef __weak 53 #define __weak __attribute__((weak)) 54 #endif 55 56 /* 57 * Use __hidden attribute to mark a non-static BPF subprogram effectively 58 * static for BPF verifier's verification algorithm purposes, allowing more 59 * extensive and permissive BPF verification process, taking into account 60 * subprogram's caller context. 61 */ 62 #define __hidden __attribute__((visibility("hidden"))) 63 64 /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include 65 * any system-level headers (such as stddef.h, linux/version.h, etc), and 66 * commonly-used macros like NULL and KERNEL_VERSION aren't available through 67 * vmlinux.h. This just adds unnecessary hurdles and forces users to re-define 68 * them on their own. So as a convenience, provide such definitions here. 69 */ 70 #ifndef NULL 71 #define NULL ((void *)0) 72 #endif 73 74 #ifndef KERNEL_VERSION 75 #define KERNEL_VERSION(a, b, c) (((a) << 16) + ((b) << 8) + ((c) > 255 ? 255 : (c))) 76 #endif 77 78 /* 79 * Helper macros to manipulate data structures 80 */ 81 82 /* offsetof() definition that uses __builtin_offset() might not preserve field 83 * offset CO-RE relocation properly, so force-redefine offsetof() using 84 * old-school approach which works with CO-RE correctly 85 */ 86 #undef offsetof 87 #define offsetof(type, member) ((unsigned long)&((type *)0)->member) 88 89 /* redefined container_of() to ensure we use the above offsetof() macro */ 90 #undef container_of 91 #define container_of(ptr, type, member) \ 92 ({ \ 93 void *__mptr = (void *)(ptr); \ 94 ((type *)(__mptr - offsetof(type, member))); \ 95 }) 96 97 /* 98 * Compiler (optimization) barrier. 99 */ 100 #ifndef barrier 101 #define barrier() asm volatile("" ::: "memory") 102 #endif 103 104 /* Variable-specific compiler (optimization) barrier. It's a no-op which makes 105 * compiler believe that there is some black box modification of a given 106 * variable and thus prevents compiler from making extra assumption about its 107 * value and potential simplifications and optimizations on this variable. 108 * 109 * E.g., compiler might often delay or even omit 32-bit to 64-bit casting of 110 * a variable, making some code patterns unverifiable. Putting barrier_var() 111 * in place will ensure that cast is performed before the barrier_var() 112 * invocation, because compiler has to pessimistically assume that embedded 113 * asm section might perform some extra operations on that variable. 114 * 115 * This is a variable-specific variant of more global barrier(). 116 */ 117 #ifndef barrier_var 118 #define barrier_var(var) asm volatile("" : "+r"(var)) 119 #endif 120 121 /* 122 * Helper macro to throw a compilation error if __bpf_unreachable() gets 123 * built into the resulting code. This works given BPF back end does not 124 * implement __builtin_trap(). This is useful to assert that certain paths 125 * of the program code are never used and hence eliminated by the compiler. 126 * 127 * For example, consider a switch statement that covers known cases used by 128 * the program. __bpf_unreachable() can then reside in the default case. If 129 * the program gets extended such that a case is not covered in the switch 130 * statement, then it will throw a build error due to the default case not 131 * being compiled out. 132 */ 133 #ifndef __bpf_unreachable 134 # define __bpf_unreachable() __builtin_trap() 135 #endif 136 137 /* 138 * Helper function to perform a tail call with a constant/immediate map slot. 139 */ 140 #if (defined(__clang__) && __clang_major__ >= 8) || (!defined(__clang__) && __GNUC__ > 12) 141 #if defined(__bpf__) 142 static __always_inline void 143 bpf_tail_call_static(void *ctx, const void *map, const __u32 slot) 144 { 145 if (!__builtin_constant_p(slot)) 146 __bpf_unreachable(); 147 148 /* 149 * Provide a hard guarantee that LLVM won't optimize setting r2 (map 150 * pointer) and r3 (constant map index) from _different paths_ ending 151 * up at the _same_ call insn as otherwise we won't be able to use the 152 * jmpq/nopl retpoline-free patching by the x86-64 JIT in the kernel 153 * given they mismatch. See also d2e4c1e6c294 ("bpf: Constant map key 154 * tracking for prog array pokes") for details on verifier tracking. 155 * 156 * Note on clobber list: we need to stay in-line with BPF calling 157 * convention, so even if we don't end up using r0, r4, r5, we need 158 * to mark them as clobber so that LLVM doesn't end up using them 159 * before / after the call. 160 */ 161 asm volatile("r1 = %[ctx]\n\t" 162 "r2 = %[map]\n\t" 163 "r3 = %[slot]\n\t" 164 "call 12" 165 :: [ctx]"r"(ctx), [map]"r"(map), [slot]"i"(slot) 166 : "r0", "r1", "r2", "r3", "r4", "r5"); 167 } 168 #endif 169 #endif 170 171 enum libbpf_pin_type { 172 LIBBPF_PIN_NONE, 173 /* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */ 174 LIBBPF_PIN_BY_NAME, 175 }; 176 177 enum libbpf_tristate { 178 TRI_NO = 0, 179 TRI_YES = 1, 180 TRI_MODULE = 2, 181 }; 182 183 #define __kconfig __attribute__((section(".kconfig"))) 184 #define __ksym __attribute__((section(".ksyms"))) 185 #define __kptr_untrusted __attribute__((btf_type_tag("kptr_untrusted"))) 186 #define __kptr __attribute__((btf_type_tag("kptr"))) 187 #define __percpu_kptr __attribute__((btf_type_tag("percpu_kptr"))) 188 189 #if defined (__clang__) 190 #define bpf_ksym_exists(sym) ({ \ 191 _Static_assert(!__builtin_constant_p(!!sym), \ 192 #sym " should be marked as __weak"); \ 193 !!sym; \ 194 }) 195 #elif __GNUC__ > 8 196 #define bpf_ksym_exists(sym) ({ \ 197 _Static_assert(__builtin_has_attribute (*sym, __weak__), \ 198 #sym " should be marked as __weak"); \ 199 !!sym; \ 200 }) 201 #else 202 #define bpf_ksym_exists(sym) !!sym 203 #endif 204 205 #define __arg_ctx __attribute__((btf_decl_tag("arg:ctx"))) 206 #define __arg_nonnull __attribute((btf_decl_tag("arg:nonnull"))) 207 #define __arg_nullable __attribute((btf_decl_tag("arg:nullable"))) 208 #define __arg_trusted __attribute((btf_decl_tag("arg:trusted"))) 209 #define __arg_arena __attribute((btf_decl_tag("arg:arena"))) 210 211 #ifndef ___bpf_concat 212 #define ___bpf_concat(a, b) a ## b 213 #endif 214 #ifndef ___bpf_apply 215 #define ___bpf_apply(fn, n) ___bpf_concat(fn, n) 216 #endif 217 #ifndef ___bpf_nth 218 #define ___bpf_nth(_, _1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c, N, ...) N 219 #endif 220 #ifndef ___bpf_narg 221 #define ___bpf_narg(...) \ 222 ___bpf_nth(_, ##__VA_ARGS__, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0) 223 #endif 224 225 #define ___bpf_fill0(arr, p, x) do {} while (0) 226 #define ___bpf_fill1(arr, p, x) arr[p] = x 227 #define ___bpf_fill2(arr, p, x, args...) arr[p] = x; ___bpf_fill1(arr, p + 1, args) 228 #define ___bpf_fill3(arr, p, x, args...) arr[p] = x; ___bpf_fill2(arr, p + 1, args) 229 #define ___bpf_fill4(arr, p, x, args...) arr[p] = x; ___bpf_fill3(arr, p + 1, args) 230 #define ___bpf_fill5(arr, p, x, args...) arr[p] = x; ___bpf_fill4(arr, p + 1, args) 231 #define ___bpf_fill6(arr, p, x, args...) arr[p] = x; ___bpf_fill5(arr, p + 1, args) 232 #define ___bpf_fill7(arr, p, x, args...) arr[p] = x; ___bpf_fill6(arr, p + 1, args) 233 #define ___bpf_fill8(arr, p, x, args...) arr[p] = x; ___bpf_fill7(arr, p + 1, args) 234 #define ___bpf_fill9(arr, p, x, args...) arr[p] = x; ___bpf_fill8(arr, p + 1, args) 235 #define ___bpf_fill10(arr, p, x, args...) arr[p] = x; ___bpf_fill9(arr, p + 1, args) 236 #define ___bpf_fill11(arr, p, x, args...) arr[p] = x; ___bpf_fill10(arr, p + 1, args) 237 #define ___bpf_fill12(arr, p, x, args...) arr[p] = x; ___bpf_fill11(arr, p + 1, args) 238 #define ___bpf_fill(arr, args...) \ 239 ___bpf_apply(___bpf_fill, ___bpf_narg(args))(arr, 0, args) 240 241 /* 242 * BPF_SEQ_PRINTF to wrap bpf_seq_printf to-be-printed values 243 * in a structure. 244 */ 245 #define BPF_SEQ_PRINTF(seq, fmt, args...) \ 246 ({ \ 247 static const char ___fmt[] = fmt; \ 248 unsigned long long ___param[___bpf_narg(args)]; \ 249 \ 250 _Pragma("GCC diagnostic push") \ 251 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \ 252 ___bpf_fill(___param, args); \ 253 _Pragma("GCC diagnostic pop") \ 254 \ 255 bpf_seq_printf(seq, ___fmt, sizeof(___fmt), \ 256 ___param, sizeof(___param)); \ 257 }) 258 259 /* 260 * BPF_SNPRINTF wraps the bpf_snprintf helper with variadic arguments instead of 261 * an array of u64. 262 */ 263 #define BPF_SNPRINTF(out, out_size, fmt, args...) \ 264 ({ \ 265 static const char ___fmt[] = fmt; \ 266 unsigned long long ___param[___bpf_narg(args)]; \ 267 \ 268 _Pragma("GCC diagnostic push") \ 269 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \ 270 ___bpf_fill(___param, args); \ 271 _Pragma("GCC diagnostic pop") \ 272 \ 273 bpf_snprintf(out, out_size, ___fmt, \ 274 ___param, sizeof(___param)); \ 275 }) 276 277 #ifdef BPF_NO_GLOBAL_DATA 278 #define BPF_PRINTK_FMT_MOD 279 #else 280 #define BPF_PRINTK_FMT_MOD static const 281 #endif 282 283 #define __bpf_printk(fmt, ...) \ 284 ({ \ 285 BPF_PRINTK_FMT_MOD char ____fmt[] = fmt; \ 286 bpf_trace_printk(____fmt, sizeof(____fmt), \ 287 ##__VA_ARGS__); \ 288 }) 289 290 /* 291 * __bpf_vprintk wraps the bpf_trace_vprintk helper with variadic arguments 292 * instead of an array of u64. 293 */ 294 #define __bpf_vprintk(fmt, args...) \ 295 ({ \ 296 static const char ___fmt[] = fmt; \ 297 unsigned long long ___param[___bpf_narg(args)]; \ 298 \ 299 _Pragma("GCC diagnostic push") \ 300 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \ 301 ___bpf_fill(___param, args); \ 302 _Pragma("GCC diagnostic pop") \ 303 \ 304 bpf_trace_vprintk(___fmt, sizeof(___fmt), \ 305 ___param, sizeof(___param)); \ 306 }) 307 308 /* Use __bpf_printk when bpf_printk call has 3 or fewer fmt args 309 * Otherwise use __bpf_vprintk 310 */ 311 #define ___bpf_pick_printk(...) \ 312 ___bpf_nth(_, ##__VA_ARGS__, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \ 313 __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \ 314 __bpf_vprintk, __bpf_vprintk, __bpf_printk /*3*/, __bpf_printk /*2*/,\ 315 __bpf_printk /*1*/, __bpf_printk /*0*/) 316 317 /* Helper macro to print out debug messages */ 318 #define bpf_printk(fmt, args...) ___bpf_pick_printk(args)(fmt, ##args) 319 320 struct bpf_iter_num; 321 322 extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __weak __ksym; 323 extern int *bpf_iter_num_next(struct bpf_iter_num *it) __weak __ksym; 324 extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __weak __ksym; 325 326 #ifndef bpf_for_each 327 /* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for 328 * using BPF open-coded iterators without having to write mundane explicit 329 * low-level loop logic. Instead, it provides for()-like generic construct 330 * that can be used pretty naturally. E.g., for some hypothetical cgroup 331 * iterator, you'd write: 332 * 333 * struct cgroup *cg, *parent_cg = <...>; 334 * 335 * bpf_for_each(cgroup, cg, parent_cg, CG_ITER_CHILDREN) { 336 * bpf_printk("Child cgroup id = %d", cg->cgroup_id); 337 * if (cg->cgroup_id == 123) 338 * break; 339 * } 340 * 341 * I.e., it looks almost like high-level for each loop in other languages, 342 * supports continue/break, and is verifiable by BPF verifier. 343 * 344 * For iterating integers, the difference betwen bpf_for_each(num, i, N, M) 345 * and bpf_for(i, N, M) is in that bpf_for() provides additional proof to 346 * verifier that i is in [N, M) range, and in bpf_for_each() case i is `int 347 * *`, not just `int`. So for integers bpf_for() is more convenient. 348 * 349 * Note: this macro relies on C99 feature of allowing to declare variables 350 * inside for() loop, bound to for() loop lifetime. It also utilizes GCC 351 * extension: __attribute__((cleanup(<func>))), supported by both GCC and 352 * Clang. 353 */ 354 #define bpf_for_each(type, cur, args...) for ( \ 355 /* initialize and define destructor */ \ 356 struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */, \ 357 cleanup(bpf_iter_##type##_destroy))), \ 358 /* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */ \ 359 *___p __attribute__((unused)) = ( \ 360 bpf_iter_##type##_new(&___it, ##args), \ 361 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \ 362 /* for bpf_iter_##type##_destroy() when used from cleanup() attribute */ \ 363 (void)bpf_iter_##type##_destroy, (void *)0); \ 364 /* iteration and termination check */ \ 365 (((cur) = bpf_iter_##type##_next(&___it))); \ 366 ) 367 #endif /* bpf_for_each */ 368 369 #ifndef bpf_for 370 /* bpf_for(i, start, end) implements a for()-like looping construct that sets 371 * provided integer variable *i* to values starting from *start* through, 372 * but not including, *end*. It also proves to BPF verifier that *i* belongs 373 * to range [start, end), so this can be used for accessing arrays without 374 * extra checks. 375 * 376 * Note: *start* and *end* are assumed to be expressions with no side effects 377 * and whose values do not change throughout bpf_for() loop execution. They do 378 * not have to be statically known or constant, though. 379 * 380 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for() 381 * loop bound variables and cleanup attribute, supported by GCC and Clang. 382 */ 383 #define bpf_for(i, start, end) for ( \ 384 /* initialize and define destructor */ \ 385 struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \ 386 cleanup(bpf_iter_num_destroy))), \ 387 /* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \ 388 *___p __attribute__((unused)) = ( \ 389 bpf_iter_num_new(&___it, (start), (end)), \ 390 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \ 391 /* for bpf_iter_num_destroy() when used from cleanup() attribute */ \ 392 (void)bpf_iter_num_destroy, (void *)0); \ 393 ({ \ 394 /* iteration step */ \ 395 int *___t = bpf_iter_num_next(&___it); \ 396 /* termination and bounds check */ \ 397 (___t && ((i) = *___t, (i) >= (start) && (i) < (end))); \ 398 }); \ 399 ) 400 #endif /* bpf_for */ 401 402 #ifndef bpf_repeat 403 /* bpf_repeat(N) performs N iterations without exposing iteration number 404 * 405 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for() 406 * loop bound variables and cleanup attribute, supported by GCC and Clang. 407 */ 408 #define bpf_repeat(N) for ( \ 409 /* initialize and define destructor */ \ 410 struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \ 411 cleanup(bpf_iter_num_destroy))), \ 412 /* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \ 413 *___p __attribute__((unused)) = ( \ 414 bpf_iter_num_new(&___it, 0, (N)), \ 415 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \ 416 /* for bpf_iter_num_destroy() when used from cleanup() attribute */ \ 417 (void)bpf_iter_num_destroy, (void *)0); \ 418 bpf_iter_num_next(&___it); \ 419 /* nothing here */ \ 420 ) 421 #endif /* bpf_repeat */ 422 423 #endif 424