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-rw-r--r--samples/bpf/bpf_load.c224
1 files changed, 155 insertions, 69 deletions
diff --git a/samples/bpf/bpf_load.c b/samples/bpf/bpf_load.c
index 4221dc359453..fedec29c7817 100644
--- a/samples/bpf/bpf_load.c
+++ b/samples/bpf/bpf_load.c
@@ -39,6 +39,16 @@ int event_fd[MAX_PROGS];
int prog_cnt;
int prog_array_fd = -1;
+/* Keeping relevant info on maps */
+struct bpf_map_data {
+ int fd;
+ char *name;
+ size_t elf_offset;
+ struct bpf_map_def def;
+};
+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;
@@ -186,42 +196,39 @@ static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
return 0;
}
-static int load_maps(struct bpf_map_def *maps, int nr_maps,
- const char **map_names, fixup_map_cb fixup_map)
+static int load_maps(struct bpf_map_data *maps, int nr_maps,
+ fixup_map_cb fixup_map)
{
int i;
- /*
- * Warning: Using "maps" pointing to ELF data_maps->d_buf as
- * an array of struct bpf_map_def is a wrong assumption about
- * the ELF maps section format.
- */
+
for (i = 0; i < nr_maps; i++) {
if (fixup_map)
- fixup_map(&maps[i], map_names[i], i);
+ fixup_map(&maps[i].def, maps[i].name, i);
- if (maps[i].type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
- maps[i].type == BPF_MAP_TYPE_HASH_OF_MAPS) {
- int inner_map_fd = map_fd[maps[i].inner_map_idx];
+ 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(maps[i].type,
- maps[i].key_size,
- inner_map_fd,
- maps[i].max_entries,
- maps[i].map_flags);
+ map_fd[i] = bpf_create_map_in_map(maps[i].def.type,
+ maps[i].def.key_size,
+ inner_map_fd,
+ maps[i].def.max_entries,
+ maps[i].def.map_flags);
} else {
- map_fd[i] = bpf_create_map(maps[i].type,
- maps[i].key_size,
- maps[i].value_size,
- maps[i].max_entries,
- maps[i].map_flags);
+ map_fd[i] = bpf_create_map(maps[i].def.type,
+ maps[i].def.key_size,
+ maps[i].def.value_size,
+ maps[i].def.max_entries,
+ maps[i].def.map_flags);
}
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].type == BPF_MAP_TYPE_PROG_ARRAY)
+ if (maps[i].def.type == BPF_MAP_TYPE_PROG_ARRAY)
prog_array_fd = map_fd[i];
}
return 0;
@@ -251,7 +258,8 @@ static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
}
static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
- GElf_Shdr *shdr, struct bpf_insn *insn)
+ GElf_Shdr *shdr, struct bpf_insn *insn,
+ struct bpf_map_data *maps, int nr_maps)
{
int i, nrels;
@@ -261,6 +269,8 @@ static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
GElf_Sym sym;
GElf_Rel rel;
unsigned int insn_idx;
+ bool match = false;
+ int j, map_idx;
gelf_getrel(data, i, &rel);
@@ -274,11 +284,21 @@ static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
return 1;
}
insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
- /*
- * Warning: Using sizeof(struct bpf_map_def) here is a
- * wrong assumption about ELF maps section format
- */
- insn[insn_idx].imm = map_fd[sym.st_value / sizeof(struct bpf_map_def)];
+
+ /* 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;
@@ -297,40 +317,112 @@ static int cmp_symbols(const void *l, const void *r)
return 0;
}
-static int get_sorted_map_names(Elf *elf, Elf_Data *symbols, int maps_shndx,
- int strtabidx, char **map_names)
+static int load_elf_maps_section(struct bpf_map_data *maps, int maps_shndx,
+ Elf *elf, Elf_Data *symbols, int strtabidx)
{
- GElf_Sym map_symbols[MAX_MAPS];
- int i, nr_maps = 0;
+ 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 (i = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) {
- assert(nr_maps < MAX_MAPS);
- if (!gelf_getsym(symbols, i, &map_symbols[nr_maps]))
+ /* 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 (map_symbols[nr_maps].st_shndx != maps_shndx)
+ if (sym[nr_maps].st_shndx != maps_shndx)
continue;
+ /* Only increment iif maps section */
nr_maps++;
}
- qsort(map_symbols, nr_maps, sizeof(GElf_Sym), cmp_symbols);
+ /* 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++) {
- char *map_name;
-
- map_name = elf_strptr(elf, strtabidx, map_symbols[i].st_name);
- if (!map_name) {
- printf("cannot get map symbol\n");
- return -1;
- }
-
- map_names[i] = strdup(map_name);
- if (!map_names[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);
- return -1;
+ 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;
}
@@ -341,7 +433,8 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
GElf_Ehdr ehdr;
GElf_Shdr shdr, shdr_prog;
Elf_Data *data, *data_prog, *data_maps = NULL, *symbols = NULL;
- char *shname, *shname_prog, *map_names[MAX_MAPS] = { NULL };
+ char *shname, *shname_prog;
+ int nr_maps = 0;
/* reset global variables */
kern_version = 0;
@@ -389,8 +482,12 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
}
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;
@@ -405,27 +502,17 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
}
if (data_maps) {
- int nr_maps;
- int prog_elf_map_sz;
-
- nr_maps = get_sorted_map_names(elf, symbols, maps_shndx,
- strtabidx, map_names);
- if (nr_maps < 0)
- goto done;
-
- /* Deduce map struct size stored in ELF maps section */
- prog_elf_map_sz = data_maps->d_size / nr_maps;
- if (prog_elf_map_sz != sizeof(struct bpf_map_def)) {
- printf("Error: ELF maps sec wrong size (%d/%lu),"
- " old kern.o file?\n",
- prog_elf_map_sz, sizeof(struct bpf_map_def));
+ 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(data_maps->d_buf, nr_maps,
- (const char **)map_names, fixup_map))
+ if (load_maps(map_data, nr_maps, fixup_map))
goto done;
+ map_data_count = nr_maps;
processed_sec[maps_shndx] = true;
}
@@ -453,7 +540,8 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
processed_sec[shdr.sh_info] = true;
processed_sec[i] = true;
- if (parse_relo_and_apply(data, symbols, &shdr, insns))
+ if (parse_relo_and_apply(data, symbols, &shdr, insns,
+ map_data, nr_maps))
continue;
if (memcmp(shname_prog, "kprobe/", 7) == 0 ||
@@ -488,8 +576,6 @@ static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
ret = 0;
done:
- for (i = 0; i < MAX_MAPS; i++)
- free(map_names[i]);
close(fd);
return ret;
}