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authorCraig Gallek <kraig@google.com>2017-10-05 17:41:57 +0300
committerDavid S. Miller <davem@davemloft.net>2017-10-06 07:42:28 +0300
commitb13c5c14dbfd5923d773de9661404ed9600c53ef (patch)
treecfb266d6bb37d00da439d028930d34691ae8e1c0 /tools
parentd009313c99ba575b65a944fe2c683c6346ea1721 (diff)
downloadlinux-b13c5c14dbfd5923d773de9661404ed9600c53ef.tar.xz
libbpf: parse maps sections of varying size
This library previously assumed a fixed-size map options structure. Any new options were ignored. In order to allow the options structure to grow and to support parsing older programs, this patch updates the maps section parsing to handle varying sizes. Object files with maps sections smaller than expected will have the new fields initialized to zero. Object files which have larger than expected maps sections will be rejected unless all of the unrecognized data is zero. This change still assumes that each map definition in the maps section is the same size. Signed-off-by: Craig Gallek <kraig@google.com> Acked-by: Jesper Dangaard Brouer <brouer@redhat.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'tools')
-rw-r--r--tools/lib/bpf/libbpf.c70
1 files changed, 41 insertions, 29 deletions
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4f402dcdf372..23152890ec60 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -579,31 +579,6 @@ bpf_object__init_kversion(struct bpf_object *obj,
return 0;
}
-static int
-bpf_object__validate_maps(struct bpf_object *obj)
-{
- int i;
-
- /*
- * If there's only 1 map, the only error case should have been
- * catched in bpf_object__init_maps().
- */
- if (!obj->maps || !obj->nr_maps || (obj->nr_maps == 1))
- return 0;
-
- for (i = 1; i < obj->nr_maps; i++) {
- const struct bpf_map *a = &obj->maps[i - 1];
- const struct bpf_map *b = &obj->maps[i];
-
- if (b->offset - a->offset < sizeof(struct bpf_map_def)) {
- pr_warning("corrupted map section in %s: map \"%s\" too small\n",
- obj->path, a->name);
- return -EINVAL;
- }
- }
- return 0;
-}
-
static int compare_bpf_map(const void *_a, const void *_b)
{
const struct bpf_map *a = _a;
@@ -615,7 +590,7 @@ static int compare_bpf_map(const void *_a, const void *_b)
static int
bpf_object__init_maps(struct bpf_object *obj)
{
- int i, map_idx, nr_maps = 0;
+ int i, map_idx, map_def_sz, nr_maps = 0;
Elf_Scn *scn;
Elf_Data *data;
Elf_Data *symbols = obj->efile.symbols;
@@ -658,6 +633,15 @@ bpf_object__init_maps(struct bpf_object *obj)
if (!nr_maps)
return 0;
+ /* Assume equally sized map definitions */
+ map_def_sz = data->d_size / nr_maps;
+ if (!data->d_size || (data->d_size % nr_maps) != 0) {
+ pr_warning("unable to determine map definition size "
+ "section %s, %d maps in %zd bytes\n",
+ obj->path, nr_maps, data->d_size);
+ return -EINVAL;
+ }
+
obj->maps = calloc(nr_maps, sizeof(obj->maps[0]));
if (!obj->maps) {
pr_warning("alloc maps for object failed\n");
@@ -690,7 +674,7 @@ bpf_object__init_maps(struct bpf_object *obj)
obj->efile.strtabidx,
sym.st_name);
obj->maps[map_idx].offset = sym.st_value;
- if (sym.st_value + sizeof(struct bpf_map_def) > data->d_size) {
+ if (sym.st_value + map_def_sz > data->d_size) {
pr_warning("corrupted maps section in %s: last map \"%s\" too small\n",
obj->path, map_name);
return -EINVAL;
@@ -704,12 +688,40 @@ bpf_object__init_maps(struct bpf_object *obj)
pr_debug("map %d is \"%s\"\n", map_idx,
obj->maps[map_idx].name);
def = (struct bpf_map_def *)(data->d_buf + sym.st_value);
- obj->maps[map_idx].def = *def;
+ /*
+ * If the definition of the map in the object file fits in
+ * bpf_map_def, copy it. Any extra fields in our version
+ * of bpf_map_def will default to zero as a result of the
+ * calloc above.
+ */
+ if (map_def_sz <= sizeof(struct bpf_map_def)) {
+ memcpy(&obj->maps[map_idx].def, def, map_def_sz);
+ } else {
+ /*
+ * Here the map structure being read is bigger than what
+ * we expect, truncate if the excess bits are all zero.
+ * If they are not zero, reject this map as
+ * incompatible.
+ */
+ char *b;
+ for (b = ((char *)def) + sizeof(struct bpf_map_def);
+ b < ((char *)def) + map_def_sz; b++) {
+ if (*b != 0) {
+ pr_warning("maps section in %s: \"%s\" "
+ "has unrecognized, non-zero "
+ "options\n",
+ obj->path, map_name);
+ return -EINVAL;
+ }
+ }
+ memcpy(&obj->maps[map_idx].def, def,
+ sizeof(struct bpf_map_def));
+ }
map_idx++;
}
qsort(obj->maps, obj->nr_maps, sizeof(obj->maps[0]), compare_bpf_map);
- return bpf_object__validate_maps(obj);
+ return 0;
}
static int bpf_object__elf_collect(struct bpf_object *obj)