On 2/27/24 12:45, Eduard Zingerman wrote:
Make bpf_map__set_autocreate() for struct_ops maps toggle autoload
state for referenced programs.
E.g. for the BPF code below:
SEC("struct_ops/test_1") int BPF_PROG(foo) { ... }
SEC("struct_ops/test_2") int BPF_PROG(bar) { ... }
SEC(".struct_ops.link")
struct test_ops___v1 A = {
.foo = (void *)foo
};
SEC(".struct_ops.link")
struct test_ops___v2 B = {
.foo = (void *)foo,
.bar = (void *)bar,
};
And the following libbpf API calls:
bpf_map__set_autocreate(skel->maps.A, true);
bpf_map__set_autocreate(skel->maps.B, false);
The autoload would be enabled for program 'foo' and disabled for
program 'bar'.
Do not apply such toggling if program autoload state is set by a call
to bpf_program__set_autoload().
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 35 ++++++++++++++++++++++++++++++++++-
1 file changed, 34 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b39d3f2898a1..1ea3046724f8 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -446,13 +446,18 @@ struct bpf_program {
struct bpf_object *obj;
int fd;
- bool autoload;
+ bool autoload:1;
+ bool autoload_user_set:1;
bool autoattach;
bool sym_global;
bool mark_btf_static;
enum bpf_prog_type type;
enum bpf_attach_type expected_attach_type;
int exception_cb_idx;
+ /* total number of struct_ops maps with autocreate == true
+ * that reference this program
+ */
+ __u32 struct_ops_refs;
int prog_ifindex;
__u32 attach_btf_obj_fd;
@@ -4509,6 +4514,28 @@ static int bpf_get_map_info_from_fdinfo(int fd, struct bpf_map_info *info)
return 0;
}
+/* Sync autoload and autocreate state between struct_ops map and
+ * referenced programs.
+ */
+static void bpf_map__struct_ops_toggle_progs_autoload(struct bpf_map *map, bool autocreate)
+{
+ struct bpf_program *prog;
+ int i;
+
+ for (i = 0; i < btf_vlen(map->st_ops->type); ++i) {
+ prog = map->st_ops->progs[i];
+
+ if (!prog || prog->autoload_user_set)
+ continue;
+
+ if (autocreate)
+ prog->struct_ops_refs++;
+ else
+ prog->struct_ops_refs--;
+ prog->autoload = prog->struct_ops_refs != 0;
+ }
+}
+
This part is related to the other patch [1], which allows
a user to change the value of a function pointer field. The behavior of
autocreate and autoload may suprise a user if the user call
bpf_map__set_autocreate() after changing the value of a function pointer
field.
[1]
https://lore.kernel.org/all/20240227010432.714127-1-thinker.li@xxxxxxxxx/
bool bpf_map__autocreate(const struct bpf_map *map)
{
return map->autocreate;
@@ -4519,6 +4546,9 @@ int bpf_map__set_autocreate(struct bpf_map *map, bool autocreate)
if (map->obj->loaded)
return libbpf_err(-EBUSY);
+ if (map->st_ops && map->autocreate != autocreate)
+ bpf_map__struct_ops_toggle_progs_autoload(map, autocreate);
+
map->autocreate = autocreate;
return 0;
}
@@ -8801,6 +8831,7 @@ int bpf_program__set_autoload(struct bpf_program *prog, bool autoload)
return libbpf_err(-EINVAL);
prog->autoload = autoload;
+ prog->autoload_user_set = 1;
return 0;
}
@@ -9428,6 +9459,8 @@ static int bpf_object__collect_st_ops_relos(struct bpf_object *obj,
return -EINVAL;
}
+ if (map->autocreate)
+ prog->struct_ops_refs++;
st_ops->progs[member_idx] = prog;
}
