From: KP Singh <[email protected]>
As more programs (TRACING, STRUCT_OPS, and upcoming LSM) use vmlinux
BTF information, loading the BTF vmlinux information for every program
in an object is sub-optimal. The fix was originally proposed in:
https://lore.kernel.org/bpf/CAEf4BzZodr3LKJuM7QwD38BiEH02Cc1UbtnGpVkCJ00Mf+V_Qg@mail.gmail.com/
The btf_vmlinux is populated in the object if any of the programs in
the object requires it just before the programs are loaded and freed
after the programs finish loading.
Reported-by: Andrii Nakryiko <[email protected]>
Reviewed-by: Brendan Jackman <[email protected]>
Signed-off-by: KP Singh <[email protected]>
---
tools/lib/bpf/libbpf.c | 153 +++++++++++++++++++++++++++--------------
1 file changed, 101 insertions(+), 52 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 3afaca9bce1d..37d4abfc26d1 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -385,6 +385,10 @@ struct bpf_object {
struct list_head list;
struct btf *btf;
+ /* Parse and load BTF vmlinux if any of the programs in the object need
+ * it at load time.
+ */
+ struct btf *btf_vmlinux;
struct btf_ext *btf_ext;
void *priv;
@@ -633,7 +637,8 @@ find_member_by_name(const struct btf *btf, const struct btf_type *t,
}
#define STRUCT_OPS_VALUE_PREFIX "bpf_struct_ops_"
-#define STRUCT_OPS_VALUE_PREFIX_LEN (sizeof(STRUCT_OPS_VALUE_PREFIX) - 1)
+static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
+ const char *name, __u32 kind);
static int
find_struct_ops_kern_types(const struct btf *btf, const char *tname,
@@ -644,7 +649,6 @@ find_struct_ops_kern_types(const struct btf *btf, const char *tname,
const struct btf_type *kern_type, *kern_vtype;
const struct btf_member *kern_data_member;
__s32 kern_vtype_id, kern_type_id;
- char vtname[128] = STRUCT_OPS_VALUE_PREFIX;
__u32 i;
kern_type_id = btf__find_by_name_kind(btf, tname, BTF_KIND_STRUCT);
@@ -660,13 +664,11 @@ find_struct_ops_kern_types(const struct btf *btf, const char *tname,
* find "struct bpf_struct_ops_tcp_congestion_ops" from the
* btf_vmlinux.
*/
- strncat(vtname + STRUCT_OPS_VALUE_PREFIX_LEN, tname,
- sizeof(vtname) - STRUCT_OPS_VALUE_PREFIX_LEN - 1);
- kern_vtype_id = btf__find_by_name_kind(btf, vtname,
- BTF_KIND_STRUCT);
+ kern_vtype_id = find_btf_by_prefix_kind(btf, STRUCT_OPS_VALUE_PREFIX,
+ tname, BTF_KIND_STRUCT);
if (kern_vtype_id < 0) {
- pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n",
- vtname);
+ pr_warn("struct_ops init_kern: struct %s%s is not found in kernel BTF\n",
+ STRUCT_OPS_VALUE_PREFIX, tname);
return kern_vtype_id;
}
kern_vtype = btf__type_by_id(btf, kern_vtype_id);
@@ -683,8 +685,8 @@ find_struct_ops_kern_types(const struct btf *btf, const char *tname,
break;
}
if (i == btf_vlen(kern_vtype)) {
- pr_warn("struct_ops init_kern: struct %s data is not found in struct %s\n",
- tname, vtname);
+ pr_warn("struct_ops init_kern: struct %s data is not found in struct %s%s\n",
+ tname, STRUCT_OPS_VALUE_PREFIX, tname);
return -EINVAL;
}
@@ -835,7 +837,6 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map,
static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
{
- struct btf *kern_btf = NULL;
struct bpf_map *map;
size_t i;
int err;
@@ -846,20 +847,12 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj)
if (!bpf_map__is_struct_ops(map))
continue;
- if (!kern_btf) {
- kern_btf = libbpf_find_kernel_btf();
- if (IS_ERR(kern_btf))
- return PTR_ERR(kern_btf);
- }
-
- err = bpf_map__init_kern_struct_ops(map, obj->btf, kern_btf);
- if (err) {
- btf__free(kern_btf);
+ err = bpf_map__init_kern_struct_ops(map, obj->btf,
+ obj->btf_vmlinux);
+ if (err)
return err;
- }
}
- btf__free(kern_btf);
return 0;
}
@@ -2364,6 +2357,41 @@ static int bpf_object__finalize_btf(struct bpf_object *obj)
return 0;
}
+static inline bool libbpf_prog_needs_vmlinux_btf(struct bpf_program *prog)
+{
+ if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
+ return true;
+
+ /* BPF_PROG_TYPE_TRACING programs which do not attach to other programs
+ * also need vmlinux BTF
+ */
+ if (prog->type == BPF_PROG_TYPE_TRACING && !prog->attach_prog_fd)
+ return true;
+
+ return false;
+}
+
+static int bpf_object__load_vmlinux_btf(struct bpf_object *obj)
+{
+ struct bpf_program *prog;
+ int err;
+
+ bpf_object__for_each_program(prog, obj) {
+ if (libbpf_prog_needs_vmlinux_btf(prog)) {
+ obj->btf_vmlinux = libbpf_find_kernel_btf();
+ if (IS_ERR(obj->btf_vmlinux)) {
+ err = PTR_ERR(obj->btf_vmlinux);
+ pr_warn("Error loading vmlinux BTF: %d\n", err);
+ obj->btf_vmlinux = NULL;
+ return err;
+ }
+ return 0;
+ }
+ }
+
+ return 0;
+}
+
static int bpf_object__sanitize_and_load_btf(struct bpf_object *obj)
{
int err = 0;
@@ -4891,18 +4919,14 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt,
return ret;
}
-static int libbpf_find_attach_btf_id(const char *name,
- enum bpf_attach_type attach_type,
- __u32 attach_prog_fd);
+static int libbpf_find_attach_btf_id(struct bpf_program *prog);
int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver)
{
int err = 0, fd, i, btf_id;
if (prog->type == BPF_PROG_TYPE_TRACING) {
- btf_id = libbpf_find_attach_btf_id(prog->section_name,
- prog->expected_attach_type,
- prog->attach_prog_fd);
+ btf_id = libbpf_find_attach_btf_id(prog);
if (btf_id <= 0)
return btf_id;
prog->attach_btf_id = btf_id;
@@ -5280,10 +5304,15 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
err = err ? : bpf_object__resolve_externs(obj, obj->kconfig);
err = err ? : bpf_object__sanitize_and_load_btf(obj);
err = err ? : bpf_object__sanitize_maps(obj);
+ err = err ? : bpf_object__load_vmlinux_btf(obj);
err = err ? : bpf_object__init_kern_struct_ops_maps(obj);
err = err ? : bpf_object__create_maps(obj);
err = err ? : bpf_object__relocate(obj, attr->target_btf_path);
err = err ? : bpf_object__load_progs(obj, attr->log_level);
+
+ btf__free(obj->btf_vmlinux);
+ obj->btf_vmlinux = NULL;
+
if (err)
goto out;
@@ -6504,34 +6533,52 @@ static int bpf_object__collect_struct_ops_map_reloc(struct bpf_object *obj,
return -EINVAL;
}
-#define BTF_PREFIX "btf_trace_"
+#define BTF_TRACE_PREFIX "btf_trace_"
+#define BTF_MAX_NAME_SIZE 128
+
+static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix,
+ const char *name, __u32 kind)
+{
+ char btf_type_name[BTF_MAX_NAME_SIZE];
+ int ret;
+
+ ret = snprintf(btf_type_name, sizeof(btf_type_name),
+ "%s%s", prefix, name);
+ /* snprintf returns the number of characters written excluding the
+ * the terminating null. So, if >= BTF_MAX_NAME_SIZE are written, it
+ * indicates truncation.
+ */
+ if (ret < 0 || ret >= sizeof(btf_type_name))
+ return -ENAMETOOLONG;
+ return btf__find_by_name_kind(btf, btf_type_name, kind);
+}
+
+static inline int __find_vmlinux_btf_id(struct btf *btf, const char *name,
+ enum bpf_attach_type attach_type)
+{
+ int err;
+
+ if (attach_type == BPF_TRACE_RAW_TP)
+ err = find_btf_by_prefix_kind(btf, BTF_TRACE_PREFIX, name,
+ BTF_KIND_TYPEDEF);
+ else
+ err = btf__find_by_name_kind(btf, name, BTF_KIND_FUNC);
+
+ return err;
+}
+
int libbpf_find_vmlinux_btf_id(const char *name,
enum bpf_attach_type attach_type)
{
- struct btf *btf = libbpf_find_kernel_btf();
- char raw_tp_btf[128] = BTF_PREFIX;
- char *dst = raw_tp_btf + sizeof(BTF_PREFIX) - 1;
- const char *btf_name;
- int err = -EINVAL;
- __u32 kind;
+ struct btf *btf;
+ btf = libbpf_find_kernel_btf();
if (IS_ERR(btf)) {
pr_warn("vmlinux BTF is not found\n");
return -EINVAL;
}
- if (attach_type == BPF_TRACE_RAW_TP) {
- /* prepend "btf_trace_" prefix per kernel convention */
- strncat(dst, name, sizeof(raw_tp_btf) - sizeof(BTF_PREFIX));
- btf_name = raw_tp_btf;
- kind = BTF_KIND_TYPEDEF;
- } else {
- btf_name = name;
- kind = BTF_KIND_FUNC;
- }
- err = btf__find_by_name_kind(btf, btf_name, kind);
- btf__free(btf);
- return err;
+ return __find_vmlinux_btf_id(btf, name, attach_type);
}
static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
@@ -6567,10 +6614,11 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd)
return err;
}
-static int libbpf_find_attach_btf_id(const char *name,
- enum bpf_attach_type attach_type,
- __u32 attach_prog_fd)
+static int libbpf_find_attach_btf_id(struct bpf_program *prog)
{
+ enum bpf_attach_type attach_type = prog->expected_attach_type;
+ __u32 attach_prog_fd = prog->attach_prog_fd;
+ const char *name = prog->section_name;
int i, err;
if (!name)
@@ -6585,8 +6633,9 @@ static int libbpf_find_attach_btf_id(const char *name,
err = libbpf_find_prog_btf_id(name + section_defs[i].len,
attach_prog_fd);
else
- err = libbpf_find_vmlinux_btf_id(name + section_defs[i].len,
- attach_type);
+ err = __find_vmlinux_btf_id(prog->obj->btf_vmlinux,
+ name + section_defs[i].len,
+ attach_type);
if (err <= 0)
pr_warn("%s is not found in vmlinux BTF\n", name);
return err;
--
2.20.1
On Fri, Jan 17, 2020 at 1:28 PM KP Singh <[email protected]> wrote:
>
> From: KP Singh <[email protected]>
>
> As more programs (TRACING, STRUCT_OPS, and upcoming LSM) use vmlinux
> BTF information, loading the BTF vmlinux information for every program
> in an object is sub-optimal. The fix was originally proposed in:
>
> https://lore.kernel.org/bpf/CAEf4BzZodr3LKJuM7QwD38BiEH02Cc1UbtnGpVkCJ00Mf+V_Qg@mail.gmail.com/
>
> The btf_vmlinux is populated in the object if any of the programs in
> the object requires it just before the programs are loaded and freed
> after the programs finish loading.
>
> Reported-by: Andrii Nakryiko <[email protected]>
> Reviewed-by: Brendan Jackman <[email protected]>
> Signed-off-by: KP Singh <[email protected]>
> ---
Looks great!
Acked-by: Andrii Nakryiko <[email protected]>
> tools/lib/bpf/libbpf.c | 153 +++++++++++++++++++++++++++--------------
> 1 file changed, 101 insertions(+), 52 deletions(-)
>
[...]
On Fri, Jan 17, 2020 at 1:55 PM Andrii Nakryiko
<[email protected]> wrote:
>
> On Fri, Jan 17, 2020 at 1:28 PM KP Singh <[email protected]> wrote:
> >
> > From: KP Singh <[email protected]>
> >
> > As more programs (TRACING, STRUCT_OPS, and upcoming LSM) use vmlinux
> > BTF information, loading the BTF vmlinux information for every program
> > in an object is sub-optimal. The fix was originally proposed in:
> >
> > https://lore.kernel.org/bpf/CAEf4BzZodr3LKJuM7QwD38BiEH02Cc1UbtnGpVkCJ00Mf+V_Qg@mail.gmail.com/
> >
> > The btf_vmlinux is populated in the object if any of the programs in
> > the object requires it just before the programs are loaded and freed
> > after the programs finish loading.
> >
> > Reported-by: Andrii Nakryiko <[email protected]>
> > Reviewed-by: Brendan Jackman <[email protected]>
> > Signed-off-by: KP Singh <[email protected]>
> > ---
>
> Looks great!
>
> Acked-by: Andrii Nakryiko <[email protected]>
Applied. Thanks