tools/lib/bpf/bpf_helpers.h

/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
#ifndef __BPF_HELPERS__
#define __BPF_HELPERS__

/*
 * Note that bpf programs need to include either
 * vmlinux.h (auto-generated from BTF) or linux/types.h
 * in advance since bpf_helper_defs.h uses such types
 * as __u64.
 */
#include "bpf_helper_defs.h"

#define __uint(name, val) int (*name)[val]
#define __type(name, val) typeof(val) *name
#define __array(name, val) typeof(val) *name[]

/* Helper macro to print out debug messages */
#define bpf_printk(fmt, ...)				\
({							\
	char ____fmt[] = fmt;				\
	bpf_trace_printk(____fmt, sizeof(____fmt),	\
			 ##__VA_ARGS__);		\
})

/*
 * Helper macro to place programs, maps, license in
 * different sections in elf_bpf file. Section names
 * are interpreted by elf_bpf loader
 */
#define SEC(NAME) __attribute__((section(NAME), used))

#ifndef __always_inline
#define __always_inline __attribute__((always_inline))
#endif
#ifndef __noinline
#define __noinline __attribute__((noinline))
#endif
#ifndef __weak
#define __weak __attribute__((weak))
#endif

/*
 * Helper macro to manipulate data structures
 */
#ifndef offsetof
#define offsetof(TYPE, MEMBER)	((unsigned long)&((TYPE *)0)->MEMBER)
#endif
#ifndef container_of
#define container_of(ptr, type, member)				\
	({							\
		void *__mptr = (void *)(ptr);			\
		((type *)(__mptr - offsetof(type, member)));	\
	})
#endif

/*
 * Helper macro to throw a compilation error if __bpf_unreachable() gets
 * built into the resulting code. This works given BPF back end does not
 * implement __builtin_trap(). This is useful to assert that certain paths
 * of the program code are never used and hence eliminated by the compiler.
 *
 * For example, consider a switch statement that covers known cases used by
 * the program. __bpf_unreachable() can then reside in the default case. If
 * the program gets extended such that a case is not covered in the switch
 * statement, then it will throw a build error due to the default case not
 * being compiled out.
 */
#ifndef __bpf_unreachable
# define __bpf_unreachable()	__builtin_trap()
#endif

/*
 * Helper function to perform a tail call with a constant/immediate map slot.
 */
static __always_inline void
bpf_tail_call_static(void *ctx, const void *map, const __u32 slot)
{
	if (!__builtin_constant_p(slot))
		__bpf_unreachable();

	/*
	 * Provide a hard guarantee that LLVM won't optimize setting r2 (map
	 * pointer) and r3 (constant map index) from _different paths_ ending
	 * up at the _same_ call insn as otherwise we won't be able to use the
	 * jmpq/nopl retpoline-free patching by the x86-64 JIT in the kernel
	 * given they mismatch. See also d2e4c1e6c294 ("bpf: Constant map key
	 * tracking for prog array pokes") for details on verifier tracking.
	 *
	 * Note on clobber list: we need to stay in-line with BPF calling
	 * convention, so even if we don't end up using r0, r4, r5, we need
	 * to mark them as clobber so that LLVM doesn't end up using them
	 * before / after the call.
	 */
	asm volatile("r1 = %[ctx]\n\t"
		     "r2 = %[map]\n\t"
		     "r3 = %[slot]\n\t"
		     "call 12"
		     :: [ctx]"r"(ctx), [map]"r"(map), [slot]"i"(slot)
		     : "r0", "r1", "r2", "r3", "r4", "r5");
}

/*
 * Helper structure used by eBPF C program
 * to describe BPF map attributes to libbpf loader
 */
struct bpf_map_def {
	unsigned int type;
	unsigned int key_size;
	unsigned int value_size;
	unsigned int max_entries;
	unsigned int map_flags;
};

enum libbpf_pin_type {
	LIBBPF_PIN_NONE,
	/* PIN_BY_NAME: pin maps by name (in /sys/fs/bpf by default) */
	LIBBPF_PIN_BY_NAME,
};

enum libbpf_tristate {
	TRI_NO = 0,
	TRI_YES = 1,
	TRI_MODULE = 2,
};

#define __kconfig __attribute__((section(".kconfig")))
#define __ksym __attribute__((section(".ksyms")))

#endif