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