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
bpf_tail_call_static(void * ctx,const void * map,const __u32 slot)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
185 #define bpf_ksym_exists(sym) ({ \
186 _Static_assert(!__builtin_constant_p(!!sym), #sym " should be marked as __weak"); \
187 !!sym; \
188 })
189
190 #ifndef ___bpf_concat
191 #define ___bpf_concat(a, b) a ## b
192 #endif
193 #ifndef ___bpf_apply
194 #define ___bpf_apply(fn, n) ___bpf_concat(fn, n)
195 #endif
196 #ifndef ___bpf_nth
197 #define ___bpf_nth(_, _1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c, N, ...) N
198 #endif
199 #ifndef ___bpf_narg
200 #define ___bpf_narg(...) \
201 ___bpf_nth(_, ##__VA_ARGS__, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
202 #endif
203
204 #define ___bpf_fill0(arr, p, x) do {} while (0)
205 #define ___bpf_fill1(arr, p, x) arr[p] = x
206 #define ___bpf_fill2(arr, p, x, args...) arr[p] = x; ___bpf_fill1(arr, p + 1, args)
207 #define ___bpf_fill3(arr, p, x, args...) arr[p] = x; ___bpf_fill2(arr, p + 1, args)
208 #define ___bpf_fill4(arr, p, x, args...) arr[p] = x; ___bpf_fill3(arr, p + 1, args)
209 #define ___bpf_fill5(arr, p, x, args...) arr[p] = x; ___bpf_fill4(arr, p + 1, args)
210 #define ___bpf_fill6(arr, p, x, args...) arr[p] = x; ___bpf_fill5(arr, p + 1, args)
211 #define ___bpf_fill7(arr, p, x, args...) arr[p] = x; ___bpf_fill6(arr, p + 1, args)
212 #define ___bpf_fill8(arr, p, x, args...) arr[p] = x; ___bpf_fill7(arr, p + 1, args)
213 #define ___bpf_fill9(arr, p, x, args...) arr[p] = x; ___bpf_fill8(arr, p + 1, args)
214 #define ___bpf_fill10(arr, p, x, args...) arr[p] = x; ___bpf_fill9(arr, p + 1, args)
215 #define ___bpf_fill11(arr, p, x, args...) arr[p] = x; ___bpf_fill10(arr, p + 1, args)
216 #define ___bpf_fill12(arr, p, x, args...) arr[p] = x; ___bpf_fill11(arr, p + 1, args)
217 #define ___bpf_fill(arr, args...) \
218 ___bpf_apply(___bpf_fill, ___bpf_narg(args))(arr, 0, args)
219
220 /*
221 * BPF_SEQ_PRINTF to wrap bpf_seq_printf to-be-printed values
222 * in a structure.
223 */
224 #define BPF_SEQ_PRINTF(seq, fmt, args...) \
225 ({ \
226 static const char ___fmt[] = fmt; \
227 unsigned long long ___param[___bpf_narg(args)]; \
228 \
229 _Pragma("GCC diagnostic push") \
230 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
231 ___bpf_fill(___param, args); \
232 _Pragma("GCC diagnostic pop") \
233 \
234 bpf_seq_printf(seq, ___fmt, sizeof(___fmt), \
235 ___param, sizeof(___param)); \
236 })
237
238 /*
239 * BPF_SNPRINTF wraps the bpf_snprintf helper with variadic arguments instead of
240 * an array of u64.
241 */
242 #define BPF_SNPRINTF(out, out_size, fmt, args...) \
243 ({ \
244 static const char ___fmt[] = fmt; \
245 unsigned long long ___param[___bpf_narg(args)]; \
246 \
247 _Pragma("GCC diagnostic push") \
248 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
249 ___bpf_fill(___param, args); \
250 _Pragma("GCC diagnostic pop") \
251 \
252 bpf_snprintf(out, out_size, ___fmt, \
253 ___param, sizeof(___param)); \
254 })
255
256 #ifdef BPF_NO_GLOBAL_DATA
257 #define BPF_PRINTK_FMT_MOD
258 #else
259 #define BPF_PRINTK_FMT_MOD static const
260 #endif
261
262 #define __bpf_printk(fmt, ...) \
263 ({ \
264 BPF_PRINTK_FMT_MOD char ____fmt[] = fmt; \
265 bpf_trace_printk(____fmt, sizeof(____fmt), \
266 ##__VA_ARGS__); \
267 })
268
269 /*
270 * __bpf_vprintk wraps the bpf_trace_vprintk helper with variadic arguments
271 * instead of an array of u64.
272 */
273 #define __bpf_vprintk(fmt, args...) \
274 ({ \
275 static const char ___fmt[] = fmt; \
276 unsigned long long ___param[___bpf_narg(args)]; \
277 \
278 _Pragma("GCC diagnostic push") \
279 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
280 ___bpf_fill(___param, args); \
281 _Pragma("GCC diagnostic pop") \
282 \
283 bpf_trace_vprintk(___fmt, sizeof(___fmt), \
284 ___param, sizeof(___param)); \
285 })
286
287 /* Use __bpf_printk when bpf_printk call has 3 or fewer fmt args
288 * Otherwise use __bpf_vprintk
289 */
290 #define ___bpf_pick_printk(...) \
291 ___bpf_nth(_, ##__VA_ARGS__, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \
292 __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \
293 __bpf_vprintk, __bpf_vprintk, __bpf_printk /*3*/, __bpf_printk /*2*/,\
294 __bpf_printk /*1*/, __bpf_printk /*0*/)
295
296 /* Helper macro to print out debug messages */
297 #define bpf_printk(fmt, args...) ___bpf_pick_printk(args)(fmt, ##args)
298
299 struct bpf_iter_num;
300
301 extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __weak __ksym;
302 extern int *bpf_iter_num_next(struct bpf_iter_num *it) __weak __ksym;
303 extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __weak __ksym;
304
305 #ifndef bpf_for_each
306 /* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for
307 * using BPF open-coded iterators without having to write mundane explicit
308 * low-level loop logic. Instead, it provides for()-like generic construct
309 * that can be used pretty naturally. E.g., for some hypothetical cgroup
310 * iterator, you'd write:
311 *
312 * struct cgroup *cg, *parent_cg = <...>;
313 *
314 * bpf_for_each(cgroup, cg, parent_cg, CG_ITER_CHILDREN) {
315 * bpf_printk("Child cgroup id = %d", cg->cgroup_id);
316 * if (cg->cgroup_id == 123)
317 * break;
318 * }
319 *
320 * I.e., it looks almost like high-level for each loop in other languages,
321 * supports continue/break, and is verifiable by BPF verifier.
322 *
323 * For iterating integers, the difference betwen bpf_for_each(num, i, N, M)
324 * and bpf_for(i, N, M) is in that bpf_for() provides additional proof to
325 * verifier that i is in [N, M) range, and in bpf_for_each() case i is `int
326 * *`, not just `int`. So for integers bpf_for() is more convenient.
327 *
328 * Note: this macro relies on C99 feature of allowing to declare variables
329 * inside for() loop, bound to for() loop lifetime. It also utilizes GCC
330 * extension: __attribute__((cleanup(<func>))), supported by both GCC and
331 * Clang.
332 */
333 #define bpf_for_each(type, cur, args...) for ( \
334 /* initialize and define destructor */ \
335 struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */, \
336 cleanup(bpf_iter_##type##_destroy))), \
337 /* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */ \
338 *___p __attribute__((unused)) = ( \
339 bpf_iter_##type##_new(&___it, ##args), \
340 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
341 /* for bpf_iter_##type##_destroy() when used from cleanup() attribute */ \
342 (void)bpf_iter_##type##_destroy, (void *)0); \
343 /* iteration and termination check */ \
344 (((cur) = bpf_iter_##type##_next(&___it))); \
345 )
346 #endif /* bpf_for_each */
347
348 #ifndef bpf_for
349 /* bpf_for(i, start, end) implements a for()-like looping construct that sets
350 * provided integer variable *i* to values starting from *start* through,
351 * but not including, *end*. It also proves to BPF verifier that *i* belongs
352 * to range [start, end), so this can be used for accessing arrays without
353 * extra checks.
354 *
355 * Note: *start* and *end* are assumed to be expressions with no side effects
356 * and whose values do not change throughout bpf_for() loop execution. They do
357 * not have to be statically known or constant, though.
358 *
359 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
360 * loop bound variables and cleanup attribute, supported by GCC and Clang.
361 */
362 #define bpf_for(i, start, end) for ( \
363 /* initialize and define destructor */ \
364 struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
365 cleanup(bpf_iter_num_destroy))), \
366 /* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
367 *___p __attribute__((unused)) = ( \
368 bpf_iter_num_new(&___it, (start), (end)), \
369 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
370 /* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
371 (void)bpf_iter_num_destroy, (void *)0); \
372 ({ \
373 /* iteration step */ \
374 int *___t = bpf_iter_num_next(&___it); \
375 /* termination and bounds check */ \
376 (___t && ((i) = *___t, (i) >= (start) && (i) < (end))); \
377 }); \
378 )
379 #endif /* bpf_for */
380
381 #ifndef bpf_repeat
382 /* bpf_repeat(N) performs N iterations without exposing iteration number
383 *
384 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
385 * loop bound variables and cleanup attribute, supported by GCC and Clang.
386 */
387 #define bpf_repeat(N) for ( \
388 /* initialize and define destructor */ \
389 struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
390 cleanup(bpf_iter_num_destroy))), \
391 /* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
392 *___p __attribute__((unused)) = ( \
393 bpf_iter_num_new(&___it, 0, (N)), \
394 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
395 /* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
396 (void)bpf_iter_num_destroy, (void *)0); \
397 bpf_iter_num_next(&___it); \
398 /* nothing here */ \
399 )
400 #endif /* bpf_repeat */
401
402 #endif
403