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
bpf_tail_call_static(void * ctx,const void * map,const __u32 slot)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