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![Alexei Starovoitov](/assets/img/avatar_default.png)
Prepare light skeleton to be used in the kernel module and in the user space. The look and feel of lskel.h is mostly the same with the difference that for user space the skel->rodata is the same pointer before and after skel_load operation, while in the kernel the skel->rodata after skel_open and the skel->rodata after skel_load are different pointers. Typical usage of skeleton remains the same for kernel and user space: skel = my_bpf__open(); skel->rodata->my_global_var = init_val; err = my_bpf__load(skel); err = my_bpf__attach(skel); // access skel->rodata->my_global_var; // access skel->bss->another_var; Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Yonghong Song <yhs@fb.com> Acked-by: Andrii Nakryiko <andrii@kernel.org> Link: https://lore.kernel.org/bpf/20220209232001.27490-3-alexei.starovoitov@gmail.com
349 lines
8.4 KiB
C
349 lines
8.4 KiB
C
/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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/* Copyright (c) 2021 Facebook */
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#ifndef __SKEL_INTERNAL_H
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#define __SKEL_INTERNAL_H
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#ifdef __KERNEL__
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#include <linux/fdtable.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/slab.h>
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#include <linux/bpf.h>
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#else
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <sys/mman.h>
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#include <stdlib.h>
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#include "bpf.h"
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#endif
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#ifndef __NR_bpf
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# if defined(__mips__) && defined(_ABIO32)
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# define __NR_bpf 4355
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# elif defined(__mips__) && defined(_ABIN32)
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# define __NR_bpf 6319
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# elif defined(__mips__) && defined(_ABI64)
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# define __NR_bpf 5315
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# endif
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#endif
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/* This file is a base header for auto-generated *.lskel.h files.
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* Its contents will change and may become part of auto-generation in the future.
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*
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* The layout of bpf_[map|prog]_desc and bpf_loader_ctx is feature dependent
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* and will change from one version of libbpf to another and features
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* requested during loader program generation.
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*/
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struct bpf_map_desc {
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/* output of the loader prog */
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int map_fd;
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/* input for the loader prog */
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__u32 max_entries;
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__aligned_u64 initial_value;
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};
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struct bpf_prog_desc {
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int prog_fd;
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};
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enum {
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BPF_SKEL_KERNEL = (1ULL << 0),
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};
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struct bpf_loader_ctx {
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__u32 sz;
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__u32 flags;
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__u32 log_level;
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__u32 log_size;
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__u64 log_buf;
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};
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struct bpf_load_and_run_opts {
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struct bpf_loader_ctx *ctx;
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const void *data;
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const void *insns;
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__u32 data_sz;
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__u32 insns_sz;
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const char *errstr;
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};
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long bpf_sys_bpf(__u32 cmd, void *attr, __u32 attr_size);
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static inline int skel_sys_bpf(enum bpf_cmd cmd, union bpf_attr *attr,
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unsigned int size)
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{
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#ifdef __KERNEL__
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return bpf_sys_bpf(cmd, attr, size);
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#else
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return syscall(__NR_bpf, cmd, attr, size);
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#endif
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}
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#ifdef __KERNEL__
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static inline int close(int fd)
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{
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return close_fd(fd);
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}
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static inline void *skel_alloc(size_t size)
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{
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struct bpf_loader_ctx *ctx = kzalloc(size, GFP_KERNEL);
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if (!ctx)
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return NULL;
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ctx->flags |= BPF_SKEL_KERNEL;
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return ctx;
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}
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static inline void skel_free(const void *p)
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{
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kfree(p);
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}
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/* skel->bss/rodata maps are populated the following way:
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*
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* For kernel use:
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* skel_prep_map_data() allocates kernel memory that kernel module can directly access.
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* Generated lskel stores the pointer in skel->rodata and in skel->maps.rodata.initial_value.
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* The loader program will perform probe_read_kernel() from maps.rodata.initial_value.
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* skel_finalize_map_data() sets skel->rodata to point to actual value in a bpf map and
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* does maps.rodata.initial_value = ~0ULL to signal skel_free_map_data() that kvfree
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* is not nessary.
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*
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* For user space:
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* skel_prep_map_data() mmaps anon memory into skel->rodata that can be accessed directly.
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* Generated lskel stores the pointer in skel->rodata and in skel->maps.rodata.initial_value.
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* The loader program will perform copy_from_user() from maps.rodata.initial_value.
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* skel_finalize_map_data() remaps bpf array map value from the kernel memory into
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* skel->rodata address.
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*
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* The "bpftool gen skeleton -L" command generates lskel.h that is suitable for
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* both kernel and user space. The generated loader program does
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* either bpf_probe_read_kernel() or bpf_copy_from_user() from initial_value
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* depending on bpf_loader_ctx->flags.
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*/
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static inline void skel_free_map_data(void *p, __u64 addr, size_t sz)
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{
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if (addr != ~0ULL)
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kvfree(p);
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/* When addr == ~0ULL the 'p' points to
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* ((struct bpf_array *)map)->value. See skel_finalize_map_data.
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*/
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}
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static inline void *skel_prep_map_data(const void *val, size_t mmap_sz, size_t val_sz)
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{
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void *addr;
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addr = kvmalloc(val_sz, GFP_KERNEL);
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if (!addr)
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return NULL;
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memcpy(addr, val, val_sz);
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return addr;
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}
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static inline void *skel_finalize_map_data(__u64 *init_val, size_t mmap_sz, int flags, int fd)
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{
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struct bpf_map *map;
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void *addr = NULL;
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kvfree((void *) (long) *init_val);
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*init_val = ~0ULL;
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/* At this point bpf_load_and_run() finished without error and
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* 'fd' is a valid bpf map FD. All sanity checks below should succeed.
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*/
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map = bpf_map_get(fd);
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if (IS_ERR(map))
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return NULL;
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if (map->map_type != BPF_MAP_TYPE_ARRAY)
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goto out;
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addr = ((struct bpf_array *)map)->value;
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/* the addr stays valid, since FD is not closed */
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out:
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bpf_map_put(map);
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return addr;
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}
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#else
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static inline void *skel_alloc(size_t size)
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{
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return calloc(1, size);
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}
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static inline void skel_free(void *p)
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{
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free(p);
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}
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static inline void skel_free_map_data(void *p, __u64 addr, size_t sz)
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{
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munmap(p, sz);
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}
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static inline void *skel_prep_map_data(const void *val, size_t mmap_sz, size_t val_sz)
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{
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void *addr;
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addr = mmap(NULL, mmap_sz, PROT_READ | PROT_WRITE,
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MAP_SHARED | MAP_ANONYMOUS, -1, 0);
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if (addr == (void *) -1)
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return NULL;
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memcpy(addr, val, val_sz);
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return addr;
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}
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static inline void *skel_finalize_map_data(__u64 *init_val, size_t mmap_sz, int flags, int fd)
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{
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void *addr;
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addr = mmap((void *) (long) *init_val, mmap_sz, flags, MAP_SHARED | MAP_FIXED, fd, 0);
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if (addr == (void *) -1)
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return NULL;
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return addr;
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}
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#endif
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static inline int skel_closenz(int fd)
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{
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if (fd > 0)
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return close(fd);
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return -EINVAL;
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}
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#ifndef offsetofend
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#define offsetofend(TYPE, MEMBER) \
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(offsetof(TYPE, MEMBER) + sizeof((((TYPE *)0)->MEMBER)))
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#endif
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static inline int skel_map_create(enum bpf_map_type map_type,
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const char *map_name,
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__u32 key_size,
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__u32 value_size,
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__u32 max_entries)
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{
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const size_t attr_sz = offsetofend(union bpf_attr, map_extra);
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union bpf_attr attr;
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memset(&attr, 0, attr_sz);
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attr.map_type = map_type;
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strncpy(attr.map_name, map_name, sizeof(attr.map_name));
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attr.key_size = key_size;
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attr.value_size = value_size;
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attr.max_entries = max_entries;
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return skel_sys_bpf(BPF_MAP_CREATE, &attr, attr_sz);
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}
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static inline int skel_map_update_elem(int fd, const void *key,
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const void *value, __u64 flags)
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{
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const size_t attr_sz = offsetofend(union bpf_attr, flags);
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union bpf_attr attr;
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memset(&attr, 0, attr_sz);
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attr.map_fd = fd;
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attr.key = (long) key;
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attr.value = (long) value;
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attr.flags = flags;
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return skel_sys_bpf(BPF_MAP_UPDATE_ELEM, &attr, attr_sz);
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}
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static inline int skel_raw_tracepoint_open(const char *name, int prog_fd)
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{
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const size_t attr_sz = offsetofend(union bpf_attr, raw_tracepoint.prog_fd);
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union bpf_attr attr;
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memset(&attr, 0, attr_sz);
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attr.raw_tracepoint.name = (long) name;
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attr.raw_tracepoint.prog_fd = prog_fd;
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return skel_sys_bpf(BPF_RAW_TRACEPOINT_OPEN, &attr, attr_sz);
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}
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static inline int skel_link_create(int prog_fd, int target_fd,
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enum bpf_attach_type attach_type)
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{
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const size_t attr_sz = offsetofend(union bpf_attr, link_create.iter_info_len);
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union bpf_attr attr;
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memset(&attr, 0, attr_sz);
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attr.link_create.prog_fd = prog_fd;
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attr.link_create.target_fd = target_fd;
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attr.link_create.attach_type = attach_type;
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return skel_sys_bpf(BPF_LINK_CREATE, &attr, attr_sz);
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}
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#ifdef __KERNEL__
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#define set_err
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#else
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#define set_err err = -errno
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#endif
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static inline int bpf_load_and_run(struct bpf_load_and_run_opts *opts)
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{
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int map_fd = -1, prog_fd = -1, key = 0, err;
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union bpf_attr attr;
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err = map_fd = skel_map_create(BPF_MAP_TYPE_ARRAY, "__loader.map", 4, opts->data_sz, 1);
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if (map_fd < 0) {
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opts->errstr = "failed to create loader map";
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set_err;
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goto out;
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}
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err = skel_map_update_elem(map_fd, &key, opts->data, 0);
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if (err < 0) {
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opts->errstr = "failed to update loader map";
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set_err;
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goto out;
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}
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memset(&attr, 0, sizeof(attr));
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attr.prog_type = BPF_PROG_TYPE_SYSCALL;
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attr.insns = (long) opts->insns;
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attr.insn_cnt = opts->insns_sz / sizeof(struct bpf_insn);
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attr.license = (long) "Dual BSD/GPL";
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memcpy(attr.prog_name, "__loader.prog", sizeof("__loader.prog"));
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attr.fd_array = (long) &map_fd;
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attr.log_level = opts->ctx->log_level;
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attr.log_size = opts->ctx->log_size;
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attr.log_buf = opts->ctx->log_buf;
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attr.prog_flags = BPF_F_SLEEPABLE;
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err = prog_fd = skel_sys_bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
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if (prog_fd < 0) {
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opts->errstr = "failed to load loader prog";
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set_err;
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goto out;
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}
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memset(&attr, 0, sizeof(attr));
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attr.test.prog_fd = prog_fd;
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attr.test.ctx_in = (long) opts->ctx;
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attr.test.ctx_size_in = opts->ctx->sz;
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err = skel_sys_bpf(BPF_PROG_RUN, &attr, sizeof(attr));
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if (err < 0 || (int)attr.test.retval < 0) {
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opts->errstr = "failed to execute loader prog";
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if (err < 0) {
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set_err;
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} else {
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err = (int)attr.test.retval;
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#ifndef __KERNEL__
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errno = -err;
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#endif
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}
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goto out;
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}
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err = 0;
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out:
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if (map_fd >= 0)
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close(map_fd);
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if (prog_fd >= 0)
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close(prog_fd);
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return err;
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}
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#endif
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