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 __clang_major__ >= 8 && defined(__bpf__)
141 static __always_inline void
bpf_tail_call_static(void * ctx,const void * map,const __u32 slot)142 bpf_tail_call_static(void *ctx, const void *map, const __u32 slot)
143 {
144 if (!__builtin_constant_p(slot))
145 __bpf_unreachable();
146
147 /*
148 * Provide a hard guarantee that LLVM won't optimize setting r2 (map
149 * pointer) and r3 (constant map index) from _different paths_ ending
150 * up at the _same_ call insn as otherwise we won't be able to use the
151 * jmpq/nopl retpoline-free patching by the x86-64 JIT in the kernel
152 * given they mismatch. See also d2e4c1e6c294 ("bpf: Constant map key
153 * tracking for prog array pokes") for details on verifier tracking.
154 *
155 * Note on clobber list: we need to stay in-line with BPF calling
156 * convention, so even if we don't end up using r0, r4, r5, we need
157 * to mark them as clobber so that LLVM doesn't end up using them
158 * before / after the call.
159 */
160 asm volatile("r1 = %[ctx]\n\t"
161 "r2 = %[map]\n\t"
162 "r3 = %[slot]\n\t"
163 "call 12"
164 :: [ctx]"r"(ctx), [map]"r"(map), [slot]"i"(slot)
165 : "r0", "r1", "r2", "r3", "r4", "r5");
166 }
167 #endif
168
169 enum libbpf_pin_type {
170 LIBBPF_PIN_NONE,
171 /* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
172 LIBBPF_PIN_BY_NAME,
173 };
174
175 enum libbpf_tristate {
176 TRI_NO = 0,
177 TRI_YES = 1,
178 TRI_MODULE = 2,
179 };
180
181 #define __kconfig __attribute__((section(".kconfig")))
182 #define __ksym __attribute__((section(".ksyms")))
183 #define __kptr_untrusted __attribute__((btf_type_tag("kptr_untrusted")))
184 #define __kptr __attribute__((btf_type_tag("kptr")))
185 #define __percpu_kptr __attribute__((btf_type_tag("percpu_kptr")))
186
187 #define bpf_ksym_exists(sym) ({ \
188 _Static_assert(!__builtin_constant_p(!!sym), #sym " should be marked as __weak"); \
189 !!sym; \
190 })
191
192 #define __arg_ctx __attribute__((btf_decl_tag("arg:ctx")))
193 #define __arg_nonnull __attribute((btf_decl_tag("arg:nonnull")))
194 #define __arg_nullable __attribute((btf_decl_tag("arg:nullable")))
195 #define __arg_trusted __attribute((btf_decl_tag("arg:trusted")))
196 #define __arg_arena __attribute((btf_decl_tag("arg:arena")))
197
198 #ifndef ___bpf_concat
199 #define ___bpf_concat(a, b) a ## b
200 #endif
201 #ifndef ___bpf_apply
202 #define ___bpf_apply(fn, n) ___bpf_concat(fn, n)
203 #endif
204 #ifndef ___bpf_nth
205 #define ___bpf_nth(_, _1, _2, _3, _4, _5, _6, _7, _8, _9, _a, _b, _c, N, ...) N
206 #endif
207 #ifndef ___bpf_narg
208 #define ___bpf_narg(...) \
209 ___bpf_nth(_, ##__VA_ARGS__, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
210 #endif
211
212 #define ___bpf_fill0(arr, p, x) do {} while (0)
213 #define ___bpf_fill1(arr, p, x) arr[p] = x
214 #define ___bpf_fill2(arr, p, x, args...) arr[p] = x; ___bpf_fill1(arr, p + 1, args)
215 #define ___bpf_fill3(arr, p, x, args...) arr[p] = x; ___bpf_fill2(arr, p + 1, args)
216 #define ___bpf_fill4(arr, p, x, args...) arr[p] = x; ___bpf_fill3(arr, p + 1, args)
217 #define ___bpf_fill5(arr, p, x, args...) arr[p] = x; ___bpf_fill4(arr, p + 1, args)
218 #define ___bpf_fill6(arr, p, x, args...) arr[p] = x; ___bpf_fill5(arr, p + 1, args)
219 #define ___bpf_fill7(arr, p, x, args...) arr[p] = x; ___bpf_fill6(arr, p + 1, args)
220 #define ___bpf_fill8(arr, p, x, args...) arr[p] = x; ___bpf_fill7(arr, p + 1, args)
221 #define ___bpf_fill9(arr, p, x, args...) arr[p] = x; ___bpf_fill8(arr, p + 1, args)
222 #define ___bpf_fill10(arr, p, x, args...) arr[p] = x; ___bpf_fill9(arr, p + 1, args)
223 #define ___bpf_fill11(arr, p, x, args...) arr[p] = x; ___bpf_fill10(arr, p + 1, args)
224 #define ___bpf_fill12(arr, p, x, args...) arr[p] = x; ___bpf_fill11(arr, p + 1, args)
225 #define ___bpf_fill(arr, args...) \
226 ___bpf_apply(___bpf_fill, ___bpf_narg(args))(arr, 0, args)
227
228 /*
229 * BPF_SEQ_PRINTF to wrap bpf_seq_printf to-be-printed values
230 * in a structure.
231 */
232 #define BPF_SEQ_PRINTF(seq, fmt, args...) \
233 ({ \
234 static const char ___fmt[] = fmt; \
235 unsigned long long ___param[___bpf_narg(args)]; \
236 \
237 _Pragma("GCC diagnostic push") \
238 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
239 ___bpf_fill(___param, args); \
240 _Pragma("GCC diagnostic pop") \
241 \
242 bpf_seq_printf(seq, ___fmt, sizeof(___fmt), \
243 ___param, sizeof(___param)); \
244 })
245
246 /*
247 * BPF_SNPRINTF wraps the bpf_snprintf helper with variadic arguments instead of
248 * an array of u64.
249 */
250 #define BPF_SNPRINTF(out, out_size, fmt, args...) \
251 ({ \
252 static const char ___fmt[] = fmt; \
253 unsigned long long ___param[___bpf_narg(args)]; \
254 \
255 _Pragma("GCC diagnostic push") \
256 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
257 ___bpf_fill(___param, args); \
258 _Pragma("GCC diagnostic pop") \
259 \
260 bpf_snprintf(out, out_size, ___fmt, \
261 ___param, sizeof(___param)); \
262 })
263
264 #ifdef BPF_NO_GLOBAL_DATA
265 #define BPF_PRINTK_FMT_MOD
266 #else
267 #define BPF_PRINTK_FMT_MOD static const
268 #endif
269
270 #define __bpf_printk(fmt, ...) \
271 ({ \
272 BPF_PRINTK_FMT_MOD char ____fmt[] = fmt; \
273 bpf_trace_printk(____fmt, sizeof(____fmt), \
274 ##__VA_ARGS__); \
275 })
276
277 /*
278 * __bpf_vprintk wraps the bpf_trace_vprintk helper with variadic arguments
279 * instead of an array of u64.
280 */
281 #define __bpf_vprintk(fmt, args...) \
282 ({ \
283 static const char ___fmt[] = fmt; \
284 unsigned long long ___param[___bpf_narg(args)]; \
285 \
286 _Pragma("GCC diagnostic push") \
287 _Pragma("GCC diagnostic ignored \"-Wint-conversion\"") \
288 ___bpf_fill(___param, args); \
289 _Pragma("GCC diagnostic pop") \
290 \
291 bpf_trace_vprintk(___fmt, sizeof(___fmt), \
292 ___param, sizeof(___param)); \
293 })
294
295 /* Use __bpf_printk when bpf_printk call has 3 or fewer fmt args
296 * Otherwise use __bpf_vprintk
297 */
298 #define ___bpf_pick_printk(...) \
299 ___bpf_nth(_, ##__VA_ARGS__, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \
300 __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, __bpf_vprintk, \
301 __bpf_vprintk, __bpf_vprintk, __bpf_printk /*3*/, __bpf_printk /*2*/,\
302 __bpf_printk /*1*/, __bpf_printk /*0*/)
303
304 /* Helper macro to print out debug messages */
305 #define bpf_printk(fmt, args...) ___bpf_pick_printk(args)(fmt, ##args)
306
307 struct bpf_iter_num;
308
309 extern int bpf_iter_num_new(struct bpf_iter_num *it, int start, int end) __weak __ksym;
310 extern int *bpf_iter_num_next(struct bpf_iter_num *it) __weak __ksym;
311 extern void bpf_iter_num_destroy(struct bpf_iter_num *it) __weak __ksym;
312
313 #ifndef bpf_for_each
314 /* bpf_for_each(iter_type, cur_elem, args...) provides generic construct for
315 * using BPF open-coded iterators without having to write mundane explicit
316 * low-level loop logic. Instead, it provides for()-like generic construct
317 * that can be used pretty naturally. E.g., for some hypothetical cgroup
318 * iterator, you'd write:
319 *
320 * struct cgroup *cg, *parent_cg = <...>;
321 *
322 * bpf_for_each(cgroup, cg, parent_cg, CG_ITER_CHILDREN) {
323 * bpf_printk("Child cgroup id = %d", cg->cgroup_id);
324 * if (cg->cgroup_id == 123)
325 * break;
326 * }
327 *
328 * I.e., it looks almost like high-level for each loop in other languages,
329 * supports continue/break, and is verifiable by BPF verifier.
330 *
331 * For iterating integers, the difference betwen bpf_for_each(num, i, N, M)
332 * and bpf_for(i, N, M) is in that bpf_for() provides additional proof to
333 * verifier that i is in [N, M) range, and in bpf_for_each() case i is `int
334 * *`, not just `int`. So for integers bpf_for() is more convenient.
335 *
336 * Note: this macro relies on C99 feature of allowing to declare variables
337 * inside for() loop, bound to for() loop lifetime. It also utilizes GCC
338 * extension: __attribute__((cleanup(<func>))), supported by both GCC and
339 * Clang.
340 */
341 #define bpf_for_each(type, cur, args...) for ( \
342 /* initialize and define destructor */ \
343 struct bpf_iter_##type ___it __attribute__((aligned(8), /* enforce, just in case */, \
344 cleanup(bpf_iter_##type##_destroy))), \
345 /* ___p pointer is just to call bpf_iter_##type##_new() *once* to init ___it */ \
346 *___p __attribute__((unused)) = ( \
347 bpf_iter_##type##_new(&___it, ##args), \
348 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
349 /* for bpf_iter_##type##_destroy() when used from cleanup() attribute */ \
350 (void)bpf_iter_##type##_destroy, (void *)0); \
351 /* iteration and termination check */ \
352 (((cur) = bpf_iter_##type##_next(&___it))); \
353 )
354 #endif /* bpf_for_each */
355
356 #ifndef bpf_for
357 /* bpf_for(i, start, end) implements a for()-like looping construct that sets
358 * provided integer variable *i* to values starting from *start* through,
359 * but not including, *end*. It also proves to BPF verifier that *i* belongs
360 * to range [start, end), so this can be used for accessing arrays without
361 * extra checks.
362 *
363 * Note: *start* and *end* are assumed to be expressions with no side effects
364 * and whose values do not change throughout bpf_for() loop execution. They do
365 * not have to be statically known or constant, though.
366 *
367 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
368 * loop bound variables and cleanup attribute, supported by GCC and Clang.
369 */
370 #define bpf_for(i, start, end) for ( \
371 /* initialize and define destructor */ \
372 struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
373 cleanup(bpf_iter_num_destroy))), \
374 /* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
375 *___p __attribute__((unused)) = ( \
376 bpf_iter_num_new(&___it, (start), (end)), \
377 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
378 /* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
379 (void)bpf_iter_num_destroy, (void *)0); \
380 ({ \
381 /* iteration step */ \
382 int *___t = bpf_iter_num_next(&___it); \
383 /* termination and bounds check */ \
384 (___t && ((i) = *___t, (i) >= (start) && (i) < (end))); \
385 }); \
386 )
387 #endif /* bpf_for */
388
389 #ifndef bpf_repeat
390 /* bpf_repeat(N) performs N iterations without exposing iteration number
391 *
392 * Note: similarly to bpf_for_each(), it relies on C99 feature of declaring for()
393 * loop bound variables and cleanup attribute, supported by GCC and Clang.
394 */
395 #define bpf_repeat(N) for ( \
396 /* initialize and define destructor */ \
397 struct bpf_iter_num ___it __attribute__((aligned(8), /* enforce, just in case */ \
398 cleanup(bpf_iter_num_destroy))), \
399 /* ___p pointer is necessary to call bpf_iter_num_new() *once* to init ___it */ \
400 *___p __attribute__((unused)) = ( \
401 bpf_iter_num_new(&___it, 0, (N)), \
402 /* this is a workaround for Clang bug: it currently doesn't emit BTF */ \
403 /* for bpf_iter_num_destroy() when used from cleanup() attribute */ \
404 (void)bpf_iter_num_destroy, (void *)0); \
405 bpf_iter_num_next(&___it); \
406 /* nothing here */ \
407 )
408 #endif /* bpf_repeat */
409
410 #endif
411