LXR linux/tools/lib/bpf/bpf

   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__)
  76static __always_inline void
  77bpf_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 */
 108struct 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
 116enum 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
 122enum 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
 132