simple .o parser and loader using BPF syscall.
.o is a standard ELF generated by LLVM backend
It parses elf file compiled by llvm .c->.o
- parses 'maps' section and creates maps via BPF syscall
- parses 'license' section and passes it to syscall
- parses elf relocations for BPF maps and adjusts BPF_LD_IMM64 insns
by storing map_fd into insn->imm and marking such insns as BPF_PSEUDO_MAP_FD
- loads eBPF program via BPF syscall
- attaches program FD to tracepoint events
One ELF file can contain multiple BPF programs attached to multiple
tracepoint events
int load_bpf_file(char *path);
bpf_helpers.h is a set of in-kernel helper functions available to eBPF programs
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
---
samples/bpf/bpf_helpers.h | 25 +++++
samples/bpf/bpf_load.c | 232 +++++++++++++++++++++++++++++++++++++++++++++
samples/bpf/bpf_load.h | 26 +++++
3 files changed, 283 insertions(+)
create mode 100644 samples/bpf/bpf_helpers.h
create mode 100644 samples/bpf/bpf_load.c
create mode 100644 samples/bpf/bpf_load.h
diff --git a/samples/bpf/bpf_helpers.h b/samples/bpf/bpf_helpers.h
new file mode 100644
index 000000000000..1ac4cd629f63
--- /dev/null
+++ b/samples/bpf/bpf_helpers.h
@@ -0,0 +1,25 @@
+#ifndef __BPF_HELPERS_H
+#define __BPF_HELPERS_H
+
+#define SEC(NAME) __attribute__((section(NAME), used))
+
+static void *(*bpf_fetch_ptr)(void *unsafe_ptr) = (void *) BPF_FUNC_fetch_ptr;
+static unsigned long long (*bpf_fetch_u64)(void *unsafe_ptr) = (void *) BPF_FUNC_fetch_u64;
+static unsigned int (*bpf_fetch_u32)(void *unsafe_ptr) = (void *) BPF_FUNC_fetch_u32;
+static unsigned short (*bpf_fetch_u16)(void *unsafe_ptr) = (void *) BPF_FUNC_fetch_u16;
+static unsigned char (*bpf_fetch_u8)(void *unsafe_ptr) = (void *) BPF_FUNC_fetch_u8;
+static int (*bpf_printk)(const char *fmt, int fmt_size, ...) = (void *) BPF_FUNC_printk;
+static int (*bpf_memcmp)(void *unsafe_ptr, void *safe_ptr, int size) = (void *) BPF_FUNC_memcmp;
+static void *(*bpf_map_lookup_elem)(void *map, void *key) = (void*) BPF_FUNC_map_lookup_elem;
+static int (*bpf_map_update_elem)(void *map, void *key, void *value) = (void*) BPF_FUNC_map_update_elem;
+static int (*bpf_map_delete_elem)(void *map, void *key) = (void *) BPF_FUNC_map_delete_elem;
+static void (*bpf_dump_stack)(void) = (void *) BPF_FUNC_dump_stack;
+
+struct bpf_map_def {
+ int type;
+ int key_size;
+ int value_size;
+ int max_entries;
+};
+
+#endif
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
new file mode 100644
index 000000000000..0c36a2060fbb
--- /dev/null
+++ b/samples/bpf/bpf_load.c
@@ -0,0 +1,232 @@
+#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 <linux/bpf.h>
+#include <linux/filter.h>
+#include "libbpf.h"
+#include "bpf_helpers.h"
+#include "bpf_load.h"
+
+#define DEBUGFS "/sys/kernel/debug/tracing/"
+
+static char license[128];
+static bool processed_sec[128];
+int map_fd[MAX_MAPS];
+
+static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
+{
+ int fd, event_fd, err;
+ char fmt[32];
+ char path[256] = DEBUGFS;
+
+ fd = bpf_prog_load(BPF_PROG_TYPE_TRACING_FILTER, prog, size, license);
+
+ if (fd < 0) {
+ printf("err %d errno %d\n", fd, errno);
+ return fd;
+ }
+
+ snprintf(fmt, sizeof(fmt), "bpf-%d", fd);
+
+ strcat(path, event);
+ strcat(path, "/filter");
+
+ printf("writing %s -> %s\n", fmt, path);
+
+ event_fd = open(path, O_WRONLY, 0);
+ if (event_fd < 0) {
+ printf("failed to open event %s\n", event);
+ return event_fd;
+ }
+
+ err = write(event_fd, fmt, strlen(fmt));
+ (void) err;
+
+ return 0;
+}
+
+static int load_maps(struct bpf_map_def *maps, int len)
+{
+ int i;
+
+ for (i = 0; i < len / sizeof(struct bpf_map_def); i++) {
+
+ map_fd[i] = bpf_create_map(maps[i].type,
+ maps[i].key_size,
+ maps[i].value_size,
+ maps[i].max_entries);
+ if (map_fd[i] < 0)
+ return 1;
+ }
+ return 0;
+}
+
+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;
+}
+
+static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
+ GElf_Shdr *shdr, struct bpf_insn *insn)
+{
+ 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;
+
+ 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->code %d\n",
+ insn[insn_idx].code);
+ return 1;
+ }
+ insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
+ insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)];
+ }
+
+ return 0;
+}
+
+int load_bpf_file(char *path)
+{
+ int fd, i;
+ Elf *elf;
+ GElf_Ehdr ehdr;
+ GElf_Shdr shdr, shdr_prog;
+ Elf_Data *data, *data_prog, *symbols = NULL;
+ char *shname, *shname_prog;
+
+ 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;
+
+ /* 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)
+ 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, "maps") == 0) {
+ processed_sec[i] = true;
+ if (load_maps(data->d_buf, data->d_size))
+ return 1;
+ } else if (shdr.sh_type == SHT_SYMTAB) {
+ symbols = data;
+ }
+ }
+
+ /* load programs that need map fixup (relocations) */
+ for (i = 1; i < ehdr.e_shnum; i++) {
+
+ if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
+ continue;
+ if (shdr.sh_type == SHT_REL) {
+ struct bpf_insn *insns;
+
+ if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
+ &shdr_prog, &data_prog))
+ continue;
+
+ if (0)
+ printf("relo %s into %s\n", shname, shname_prog);
+
+ insns = (struct bpf_insn *) data_prog->d_buf;
+
+ processed_sec[shdr.sh_info] = true;
+ processed_sec[i] = true;
+
+ if (parse_relo_and_apply(data, symbols, &shdr, insns))
+ continue;
+
+ if (memcmp(shname_prog, "events/", sizeof("events/") - 1) == 0)
+ load_and_attach(shname_prog, insns, data_prog->d_size);
+ }
+ }
+
+ /* load programs that don't use 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 (memcmp(shname, "events/", sizeof("events/") - 1) == 0)
+ load_and_attach(shname, data->d_buf, data->d_size);
+ }
+
+ close(fd);
+ return 0;
+}
+
+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)
+ puts(buf);
+ }
+}
diff --git a/samples/bpf/bpf_load.h b/samples/bpf/bpf_load.h
new file mode 100644
index 000000000000..209190d793ff
--- /dev/null
+++ b/samples/bpf/bpf_load.h
@@ -0,0 +1,26 @@
+#ifndef __BPF_LOAD_H
+#define __BPF_LOAD_H
+
+#define MAX_MAPS 64
+
+extern int map_fd[MAX_MAPS];
+
+/* parses elf file compiled by llvm .c->.o
+ * . parses 'maps' section and creates maps via BPF syscall
+ * . parses 'license' section and passes it to syscall
+ * . parses elf relocations for BPF maps and adjusts BPF_LD_IMM64 insns by
+ * storing map_fd into insn->imm and marking such insns as BPF_PSEUDO_MAP_FD
+ * . loads eBPF program via BPF syscall
+ * . attaches program FD to tracepoint events
+ *
+ * One ELF file can contain multiple BPF programs attached to multiple
+ * tracepoint events
+ *
+ * returns zero on success
+ */
+int load_bpf_file(char *path);
+
+/* forever reads /sys/.../trace_pipe */
+void read_trace_pipe(void);
+
+#endif
--
1.7.9.5
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