cregit-Linux how code gets into the kernel

Release 4.16 samples/bpf/bpf_load.c

Directory: samples/bpf
// SPDX-License-Identifier: GPL-2.0
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libelf.h>
#include <gelf.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <stdbool.h>
#include <stdlib.h>
#include <linux/bpf.h>
#include <linux/filter.h>
#include <linux/perf_event.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <linux/types.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <poll.h>
#include <ctype.h>
#include <assert.h>
#include "libbpf.h"
#include "bpf_load.h"
#include "perf-sys.h"


#define DEBUGFS "/sys/kernel/debug/tracing/"


static char license[128];

static int kern_version;

static bool processed_sec[128];

char bpf_log_buf[BPF_LOG_BUF_SIZE];

int map_fd[MAX_MAPS];

int prog_fd[MAX_PROGS];

int event_fd[MAX_PROGS];

int prog_cnt;

int prog_array_fd = -1;


struct bpf_map_data map_data[MAX_MAPS];

int map_data_count = 0;


static int populate_prog_array(const char *event, int prog_fd) { int ind = atoi(event), err; err = bpf_map_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY); if (err < 0) { printf("failed to store prog_fd in prog_array\n"); return -1; } return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov5898.31%150.00%
Joe Stringer11.69%150.00%
Total59100.00%2100.00%


static int load_and_attach(const char *event, struct bpf_insn *prog, int size) { bool is_socket = strncmp(event, "socket", 6) == 0; bool is_kprobe = strncmp(event, "kprobe/", 7) == 0; bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0; bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0; bool is_xdp = strncmp(event, "xdp", 3) == 0; bool is_perf_event = strncmp(event, "perf_event", 10) == 0; bool is_cgroup_skb = strncmp(event, "cgroup/skb", 10) == 0; bool is_cgroup_sk = strncmp(event, "cgroup/sock", 11) == 0; bool is_sockops = strncmp(event, "sockops", 7) == 0; bool is_sk_skb = strncmp(event, "sk_skb", 6) == 0; size_t insns_cnt = size / sizeof(struct bpf_insn); enum bpf_prog_type prog_type; char buf[256]; int fd, efd, err, id; struct perf_event_attr attr = {}; attr.type = PERF_TYPE_TRACEPOINT; attr.sample_type = PERF_SAMPLE_RAW; attr.sample_period = 1; attr.wakeup_events = 1; if (is_socket) { prog_type = BPF_PROG_TYPE_SOCKET_FILTER; } else if (is_kprobe || is_kretprobe) { prog_type = BPF_PROG_TYPE_KPROBE; } else if (is_tracepoint) { prog_type = BPF_PROG_TYPE_TRACEPOINT; } else if (is_xdp) { prog_type = BPF_PROG_TYPE_XDP; } else if (is_perf_event) { prog_type = BPF_PROG_TYPE_PERF_EVENT; } else if (is_cgroup_skb) { prog_type = BPF_PROG_TYPE_CGROUP_SKB; } else if (is_cgroup_sk) { prog_type = BPF_PROG_TYPE_CGROUP_SOCK; } else if (is_sockops) { prog_type = BPF_PROG_TYPE_SOCK_OPS; } else if (is_sk_skb) { prog_type = BPF_PROG_TYPE_SK_SKB; } else { printf("Unknown event '%s'\n", event); return -1; } fd = bpf_load_program(prog_type, prog, insns_cnt, license, kern_version, bpf_log_buf, BPF_LOG_BUF_SIZE); if (fd < 0) { printf("bpf_load_program() err=%d\n%s", errno, bpf_log_buf); return -1; } prog_fd[prog_cnt++] = fd; if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk) return 0; if (is_socket || is_sockops || is_sk_skb) { if (is_socket) event += 6; else event += 7; if (*event != '/') return 0; event++; if (!isdigit(*event)) { printf("invalid prog number\n"); return -1; } return populate_prog_array(event, fd); } if (is_kprobe || is_kretprobe) { if (is_kprobe) event += 7; else event += 10; if (*event == 0) { printf("event name cannot be empty\n"); return -1; } if (isdigit(*event)) return populate_prog_array(event, fd); snprintf(buf, sizeof(buf), "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events", is_kprobe ? 'p' : 'r', event, event); err = system(buf); if (err < 0) { printf("failed to create kprobe '%s' error '%s'\n", event, strerror(errno)); return -1; } strcpy(buf, DEBUGFS); strcat(buf, "events/kprobes/"); strcat(buf, event); strcat(buf, "/id"); } else if (is_tracepoint) { event += 11; if (*event == 0) { printf("event name cannot be empty\n"); return -1; } strcpy(buf, DEBUGFS); strcat(buf, "events/"); strcat(buf, event); strcat(buf, "/id"); } efd = open(buf, O_RDONLY, 0); if (efd < 0) { printf("failed to open event %s\n", event); return -1; } err = read(efd, buf, sizeof(buf)); if (err < 0 || err >= sizeof(buf)) { printf("read from '%s' failed '%s'\n", event, strerror(errno)); return -1; } close(efd); buf[err] = 0; id = atoi(buf); attr.config = id; efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0); if (efd < 0) { printf("event %d fd %d err %s\n", id, efd, strerror(errno)); return -1; } event_fd[prog_cnt - 1] = efd; err = ioctl(efd, PERF_EVENT_IOC_ENABLE, 0); if (err < 0) { printf("ioctl PERF_EVENT_IOC_ENABLE failed err %s\n", strerror(errno)); return -1; } err = ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd); if (err < 0) { printf("ioctl PERF_EVENT_IOC_SET_BPF failed err %s\n", strerror(errno)); return -1; } return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov66075.34%538.46%
David Ahern546.16%17.69%
Yonghong Song485.48%17.69%
Lawrence Brakmo364.11%17.69%
Brenden Blanco323.65%17.69%
John Fastabend273.08%17.69%
Joe Stringer192.17%323.08%
Total876100.00%13100.00%


static int load_maps(struct bpf_map_data *maps, int nr_maps, fixup_map_cb fixup_map) { int i, numa_node; for (i = 0; i < nr_maps; i++) { if (fixup_map) { fixup_map(&maps[i], i); /* Allow userspace to assign map FD prior to creation */ if (maps[i].fd != -1) { map_fd[i] = maps[i].fd; continue; } } numa_node = maps[i].def.map_flags & BPF_F_NUMA_NODE ? maps[i].def.numa_node : -1; if (maps[i].def.type == BPF_MAP_TYPE_ARRAY_OF_MAPS || maps[i].def.type == BPF_MAP_TYPE_HASH_OF_MAPS) { int inner_map_fd = map_fd[maps[i].def.inner_map_idx]; map_fd[i] = bpf_create_map_in_map_node(maps[i].def.type, maps[i].name, maps[i].def.key_size, inner_map_fd, maps[i].def.max_entries, maps[i].def.map_flags, numa_node); } else { map_fd[i] = bpf_create_map_node(maps[i].def.type, maps[i].name, maps[i].def.key_size, maps[i].def.value_size, maps[i].def.max_entries, maps[i].def.map_flags, numa_node); } if (map_fd[i] < 0) { printf("failed to create a map: %d %s\n", errno, strerror(errno)); return 1; } maps[i].fd = map_fd[i]; if (maps[i].def.type == BPF_MAP_TYPE_PROG_ARRAY) prog_array_fd = map_fd[i]; } return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Martin KaFai Lau14243.16%436.36%
Alexei Starovoitov11835.87%436.36%
Jesper Dangaard Brouer6920.97%327.27%
Total329100.00%11100.00%


static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname, GElf_Shdr *shdr, Elf_Data **data) { Elf_Scn *scn; scn = elf_getscn(elf, i); if (!scn) return 1; if (gelf_getshdr(scn, shdr) != shdr) return 2; *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name); if (!*shname || !shdr->sh_size) return 3; *data = elf_getdata(scn, 0); if (!*data || elf_getdata(scn, *data) != NULL) return 4; return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov128100.00%1100.00%
Total128100.00%1100.00%


static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols, GElf_Shdr *shdr, struct bpf_insn *insn, struct bpf_map_data *maps, int nr_maps) { int i, nrels; nrels = shdr->sh_size / shdr->sh_entsize; for (i = 0; i < nrels; i++) { GElf_Sym sym; GElf_Rel rel; unsigned int insn_idx; bool match = false; int j, map_idx; gelf_getrel(data, i, &rel); insn_idx = rel.r_offset / sizeof(struct bpf_insn); gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym); if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) { printf("invalid relo for insn[%d].code 0x%x\n", insn_idx, insn[insn_idx].code); return 1; } insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD; /* Match FD relocation against recorded map_data[] offset */ for (map_idx = 0; map_idx < nr_maps; map_idx++) { if (maps[map_idx].elf_offset == sym.st_value) { match = true; break; } } if (match) { insn[insn_idx].imm = maps[map_idx].fd; } else { printf("invalid relo for insn[%d] no map_data match\n", insn_idx); return 1; } } return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov16068.09%150.00%
Jesper Dangaard Brouer7531.91%150.00%
Total235100.00%2100.00%


static int cmp_symbols(const void *l, const void *r) { const GElf_Sym *lsym = (const GElf_Sym *)l; const GElf_Sym *rsym = (const GElf_Sym *)r; if (lsym->st_value < rsym->st_value) return -1; else if (lsym->st_value > rsym->st_value) return 1; else return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Martin KaFai Lau7097.22%150.00%
Alexei Starovoitov22.78%150.00%
Total72100.00%2100.00%


static int load_elf_maps_section(struct bpf_map_data *maps, int maps_shndx, Elf *elf, Elf_Data *symbols, int strtabidx) { int map_sz_elf, map_sz_copy; bool validate_zero = false; Elf_Data *data_maps; int i, nr_maps; GElf_Sym *sym; Elf_Scn *scn; int copy_sz; if (maps_shndx < 0) return -EINVAL; if (!symbols) return -EINVAL; /* Get data for maps section via elf index */ scn = elf_getscn(elf, maps_shndx); if (scn) data_maps = elf_getdata(scn, NULL); if (!scn || !data_maps) { printf("Failed to get Elf_Data from maps section %d\n", maps_shndx); return -EINVAL; } /* For each map get corrosponding symbol table entry */ sym = calloc(MAX_MAPS+1, sizeof(GElf_Sym)); for (i = 0, nr_maps = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) { assert(nr_maps < MAX_MAPS+1); if (!gelf_getsym(symbols, i, &sym[nr_maps])) continue; if (sym[nr_maps].st_shndx != maps_shndx) continue; /* Only increment iif maps section */ nr_maps++; } /* Align to map_fd[] order, via sort on offset in sym.st_value */ qsort(sym, nr_maps, sizeof(GElf_Sym), cmp_symbols); /* Keeping compatible with ELF maps section changes * ------------------------------------------------ * The program size of struct bpf_map_def is known by loader * code, but struct stored in ELF file can be different. * * Unfortunately sym[i].st_size is zero. To calculate the * struct size stored in the ELF file, assume all struct have * the same size, and simply divide with number of map * symbols. */ map_sz_elf = data_maps->d_size / nr_maps; map_sz_copy = sizeof(struct bpf_map_def); if (map_sz_elf < map_sz_copy) { /* * Backward compat, loading older ELF file with * smaller struct, keeping remaining bytes zero. */ map_sz_copy = map_sz_elf; } else if (map_sz_elf > map_sz_copy) { /* * Forward compat, loading newer ELF file with larger * struct with unknown features. Assume zero means * feature not used. Thus, validate rest of struct * data is zero. */ validate_zero = true; } /* Memcpy relevant part of ELF maps data to loader maps */ for (i = 0; i < nr_maps; i++) { unsigned char *addr, *end; struct bpf_map_def *def; const char *map_name; size_t offset; map_name = elf_strptr(elf, strtabidx, sym[i].st_name); maps[i].name = strdup(map_name); if (!maps[i].name) { printf("strdup(%s): %s(%d)\n", map_name, strerror(errno), errno); free(sym); return -errno; } /* Symbol value is offset into ELF maps section data area */ offset = sym[i].st_value; def = (struct bpf_map_def *)(data_maps->d_buf + offset); maps[i].elf_offset = offset; memset(&maps[i].def, 0, sizeof(struct bpf_map_def)); memcpy(&maps[i].def, def, map_sz_copy); /* Verify no newer features were requested */ if (validate_zero) { addr = (unsigned char*) def + map_sz_copy; end = (unsigned char*) def + map_sz_elf; for (; addr < end; addr++) { if (*addr != 0) { free(sym); return -EFBIG; } } } } free(sym); return nr_maps; }

Contributors

PersonTokensPropCommitsCommitProp
Jesper Dangaard Brouer33367.27%266.67%
Martin KaFai Lau16232.73%133.33%
Total495100.00%3100.00%


static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map) { int fd, i, ret, maps_shndx = -1, strtabidx = -1; Elf *elf; GElf_Ehdr ehdr; GElf_Shdr shdr, shdr_prog; Elf_Data *data, *data_prog, *data_maps = NULL, *symbols = NULL; char *shname, *shname_prog; int nr_maps = 0; /* reset global variables */ kern_version = 0; memset(license, 0, sizeof(license)); memset(processed_sec, 0, sizeof(processed_sec)); if (elf_version(EV_CURRENT) == EV_NONE) return 1; fd = open(path, O_RDONLY, 0); if (fd < 0) return 1; elf = elf_begin(fd, ELF_C_READ, NULL); if (!elf) return 1; if (gelf_getehdr(elf, &ehdr) != &ehdr) return 1; /* clear all kprobes */ i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events"); /* scan over all elf sections to get license and map info */ for (i = 1; i < ehdr.e_shnum; i++) { if (get_sec(elf, i, &ehdr, &shname, &shdr, &data)) continue; if (0) /* helpful for llvm debugging */ printf("section %d:%s data %p size %zd link %d flags %d\n", i, shname, data->d_buf, data->d_size, shdr.sh_link, (int) shdr.sh_flags); if (strcmp(shname, "license") == 0) { processed_sec[i] = true; memcpy(license, data->d_buf, data->d_size); } else if (strcmp(shname, "version") == 0) { processed_sec[i] = true; if (data->d_size != sizeof(int)) { printf("invalid size of version section %zd\n", data->d_size); return 1; } memcpy(&kern_version, data->d_buf, sizeof(int)); } else if (strcmp(shname, "maps") == 0) { int j; maps_shndx = i; data_maps = data; for (j = 0; j < MAX_MAPS; j++) map_data[j].fd = -1; } else if (shdr.sh_type == SHT_SYMTAB) { strtabidx = shdr.sh_link; symbols = data; } } ret = 1; if (!symbols) { printf("missing SHT_SYMTAB section\n"); goto done; } if (data_maps) { nr_maps = load_elf_maps_section(map_data, maps_shndx, elf, symbols, strtabidx); if (nr_maps < 0) { printf("Error: Failed loading ELF maps (errno:%d):%s\n", nr_maps, strerror(-nr_maps)); ret = 1; goto done; } if (load_maps(map_data, nr_maps, fixup_map)) goto done; map_data_count = nr_maps; processed_sec[maps_shndx] = true; } /* process all relo sections, and rewrite bpf insns for maps */ for (i = 1; i < ehdr.e_shnum; i++) { if (processed_sec[i]) continue; if (get_sec(elf, i, &ehdr, &shname, &shdr, &data)) continue; if (shdr.sh_type == SHT_REL) { struct bpf_insn *insns; /* locate prog sec that need map fixup (relocations) */ if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog, &shdr_prog, &data_prog)) continue; if (shdr_prog.sh_type != SHT_PROGBITS || !(shdr_prog.sh_flags & SHF_EXECINSTR)) continue; insns = (struct bpf_insn *) data_prog->d_buf; processed_sec[i] = true; /* relo section */ if (parse_relo_and_apply(data, symbols, &shdr, insns, map_data, nr_maps)) continue; } } /* load programs */ for (i = 1; i < ehdr.e_shnum; i++) { if (processed_sec[i]) continue; if (get_sec(elf, i, &ehdr, &shname, &shdr, &data)) continue; if (memcmp(shname, "kprobe/", 7) == 0 || memcmp(shname, "kretprobe/", 10) == 0 || memcmp(shname, "tracepoint/", 11) == 0 || memcmp(shname, "xdp", 3) == 0 || memcmp(shname, "perf_event", 10) == 0 || memcmp(shname, "socket", 6) == 0 || memcmp(shname, "cgroup/", 7) == 0 || memcmp(shname, "sockops", 7) == 0 || memcmp(shname, "sk_skb", 6) == 0) { ret = load_and_attach(shname, data->d_buf, data->d_size); if (ret != 0) goto done; } } ret = 0; done: close(fd); return ret; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov56767.66%531.25%
Martin KaFai Lau9811.69%16.25%
Jesper Dangaard Brouer799.43%318.75%
Mickaël Salaün374.42%212.50%
Lawrence Brakmo242.86%212.50%
Brenden Blanco111.31%16.25%
David Ahern111.31%16.25%
John Fastabend111.31%16.25%
Total838100.00%16100.00%


int load_bpf_file(char *path) { return do_load_bpf_file(path, NULL); }

Contributors

PersonTokensPropCommitsCommitProp
Martin KaFai Lau17100.00%1100.00%
Total17100.00%1100.00%


int load_bpf_file_fixup_map(const char *path, fixup_map_cb fixup_map) { return do_load_bpf_file(path, fixup_map); }

Contributors

PersonTokensPropCommitsCommitProp
Martin KaFai Lau1990.48%150.00%
Alexei Starovoitov29.52%150.00%
Total21100.00%2100.00%


void read_trace_pipe(void) { int trace_fd; trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0); if (trace_fd < 0) return; while (1) { static char buf[4096]; ssize_t sz; sz = read(trace_fd, buf, sizeof(buf)); if (sz > 0) { buf[sz] = 0; puts(buf); } } }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov79100.00%1100.00%
Total79100.00%1100.00%

#define MAX_SYMS 300000 static struct ksym syms[MAX_SYMS]; static int sym_cnt;
static int ksym_cmp(const void *p1, const void *p2) { return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov39100.00%1100.00%
Total39100.00%1100.00%


int load_kallsyms(void) { FILE *f = fopen("/proc/kallsyms", "r"); char func[256], buf[256]; char symbol; void *addr; int i = 0; if (!f) return -ENOENT; while (!feof(f)) { if (!fgets(buf, sizeof(buf), f)) break; if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3) break; if (!addr) continue; syms[i].addr = (long) addr; syms[i].name = strdup(func); i++; } sym_cnt = i; qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp); return 0; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov151100.00%1100.00%
Total151100.00%1100.00%


struct ksym *ksym_search(long key) { int start = 0, end = sym_cnt; int result; while (start < end) { size_t mid = start + (end - start) / 2; result = key - syms[mid].addr; if (result < 0) end = mid; else if (result > 0) start = mid + 1; else return &syms[mid]; } if (start >= 1 && syms[start - 1].addr < key && key < syms[start].addr) /* valid ksym */ return &syms[start - 1]; /* out of range. return _stext */ return &syms[0]; }

Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov129100.00%1100.00%
Total129100.00%1100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
Alexei Starovoitov222161.08%929.03%
Jesper Dangaard Brouer57115.70%516.13%
Martin KaFai Lau52314.38%516.13%
David Ahern651.79%13.23%
Lawrence Brakmo601.65%26.45%
Yonghong Song481.32%13.23%
Brenden Blanco431.18%13.23%
John Fastabend381.05%13.23%
Mickaël Salaün371.02%26.45%
Joe Stringer290.80%39.68%
Greg Kroah-Hartman10.03%13.23%
Total3636100.00%31100.00%
Directory: samples/bpf
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