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