tools/lib/bpf/bpf_helpers.h

   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 /* Helper macro to print out debug messages */
  18 #define bpf_printk(fmt, ...)                            \
  19 ({                                                      \
  20         char ____fmt[] = fmt;                           \
  21         bpf_trace_printk(____fmt, sizeof(____fmt),      \
  22                          ##__VA_ARGS__);                \
  23 })
  24
  25 /*
  26  * Helper macro to place programs, maps, license in
  27  * different sections in elf_bpf file. Section names
  28  * are interpreted by elf_bpf loader
  29  */
  30 #define SEC(NAME) __attribute__((section(NAME), used))
  31
  32 #ifndef __always_inline
  33 #define __always_inline __attribute__((always_inline))
  34 #endif
  35 #ifndef __noinline
  36 #define __noinline __attribute__((noinline))
  37 #endif
  38 #ifndef __weak
  39 #define __weak __attribute__((weak))
  40 #endif
  41
  42 /*
  43  * Helper macro to manipulate data structures
  44  */
  45 #ifndef offsetof
  46 #define offsetof(TYPE, MEMBER)  ((unsigned long)&((TYPE *)0)->MEMBER)
  47 #endif
  48 #ifndef container_of
  49 #define container_of(ptr, type, member)                         \
  50         ({                                                      \
  51                 void *__mptr = (void *)(ptr);                   \
  52                 ((type *)(__mptr - offsetof(type, member)));    \
  53         })
  54 #endif
  55
  56 /*
  57  * Helper macro to throw a compilation error if __bpf_unreachable() gets
  58  * built into the resulting code. This works given BPF back end does not
  59  * implement __builtin_trap(). This is useful to assert that certain paths
  60  * of the program code are never used and hence eliminated by the compiler.
  61  *
  62  * For example, consider a switch statement that covers known cases used by
  63  * the program. __bpf_unreachable() can then reside in the default case. If
  64  * the program gets extended such that a case is not covered in the switch
  65  * statement, then it will throw a build error due to the default case not
  66  * being compiled out.
  67  */
  68 #ifndef __bpf_unreachable
  69 # define __bpf_unreachable()    __builtin_trap()
  70 #endif
  71
  72 /*
  73  * Helper function to perform a tail call with a constant/immediate map slot.
  74  */
  75 #if __clang_major__ >= 8 && defined(__bpf__)
  76 static __always_inline void
  77 bpf_tail_call_static(void *ctx, const void *map, const __u32 slot)
  78 {
  79         if (!__builtin_constant_p(slot))
  80                 __bpf_unreachable();
  81
  82         /*
  83          * Provide a hard guarantee that LLVM won't optimize setting r2 (map
  84          * pointer) and r3 (constant map index) from _different paths_ ending
  85          * up at the _same_ call insn as otherwise we won't be able to use the
  86          * jmpq/nopl retpoline-free patching by the x86-64 JIT in the kernel
  87          * given they mismatch. See also d2e4c1e6c294 ("bpf: Constant map key
  88          * tracking for prog array pokes") for details on verifier tracking.
  89          *
  90          * Note on clobber list: we need to stay in-line with BPF calling
  91          * convention, so even if we don't end up using r0, r4, r5, we need
  92          * to mark them as clobber so that LLVM doesn't end up using them
  93          * before / after the call.
  94          */
  95         asm volatile("r1 = %[ctx]\n\t"
  96                      "r2 = %[map]\n\t"
  97                      "r3 = %[slot]\n\t"
  98                      "call 12"
  99                      :: [ctx]"r"(ctx), [map]"r"(map), [slot]"i"(slot)
 100                      : "r0", "r1", "r2", "r3", "r4", "r5");
 101 }
 102 #endif
 103
 104 /*
 105  * Helper structure used by eBPF C program
 106  * to describe BPF map attributes to libbpf loader
 107  */
 108 struct bpf_map_def {
 109         unsigned int type;
 110         unsigned int key_size;
 111         unsigned int value_size;
 112         unsigned int max_entries;
 113         unsigned int map_flags;
 114 };
 115
 116 enum libbpf_pin_type {
 117         LIBBPF_PIN_NONE,
 118         /* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
 119         LIBBPF_PIN_BY_NAME,
 120 };
 121
 122 enum libbpf_tristate {
 123         TRI_NO = 0,
 124         TRI_YES = 1,
 125         TRI_MODULE = 2,
 126 };
 127
 128 #define __kconfig __attribute__((section(".kconfig")))
 129 #define __ksym __attribute__((section(".ksyms")))
 130
 131 #endif