Add ability for user-space programs to specify non-vmlinux BTF when attaching
BTF-powered BPF programs: raw_tp, fentry/fexit/fmod_ret, LSM, etc. For this,
attach_prog_fd (now with the alias name attach_btf_obj_fd) should specify FD
of a module or vmlinux BTF object. For backwards compatibility reasons,
0 denotes vmlinux BTF. Only kernel BTF (vmlinux or module) can be specified.
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
include/linux/btf.h | 1 +
include/uapi/linux/bpf.h | 7 ++-
kernel/bpf/btf.c | 5 +++
kernel/bpf/syscall.c | 82 +++++++++++++++++++++-------------
tools/include/uapi/linux/bpf.h | 7 ++-
5 files changed, 69 insertions(+), 33 deletions(-)
diff --git a/include/linux/btf.h b/include/linux/btf.h
index fb608e4de076..4c200f5d242b 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -90,6 +90,7 @@ int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj,
int btf_get_fd_by_id(u32 id);
u32 btf_obj_id(const struct btf *btf);
+bool btf_is_kernel(const struct btf *btf);
bool btf_member_is_reg_int(const struct btf *btf, const struct btf_type *s,
const struct btf_member *m,
u32 expected_offset, u32 expected_size);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index c3458ec1f30a..1233f14f659f 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -557,7 +557,12 @@ union bpf_attr {
__aligned_u64 line_info; /* line info */
__u32 line_info_cnt; /* number of bpf_line_info records */
__u32 attach_btf_id; /* in-kernel BTF type id to attach to */
- __u32 attach_prog_fd; /* 0 to attach to vmlinux */
+ union {
+ /* valid prog_fd to attach to bpf prog */
+ __u32 attach_prog_fd;
+ /* or valid module BTF object fd or 0 to attach to vmlinux */
+ __u32 attach_btf_obj_fd;
+ };
};
struct { /* anonymous struct used by BPF_OBJ_* commands */
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 7a19bf5bfe97..8d6bdb4f4d61 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5738,6 +5738,11 @@ u32 btf_obj_id(const struct btf *btf)
return btf->id;
}
+bool btf_is_kernel(const struct btf *btf)
+{
+ return btf->kernel_btf;
+}
+
static int btf_id_cmp_func(const void *a, const void *b)
{
const int *pa = a, *pb = b;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4fd7d9269008..1b5a053f4343 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1924,12 +1924,16 @@ static void bpf_prog_load_fixup_attach_type(union bpf_attr *attr)
static int
bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
enum bpf_attach_type expected_attach_type,
- u32 btf_id, u32 prog_fd)
+ struct btf *attach_btf, u32 btf_id,
+ struct bpf_prog *dst_prog)
{
if (btf_id) {
if (btf_id > BTF_MAX_TYPE)
return -EINVAL;
+ if (!attach_btf && !dst_prog)
+ return -EINVAL;
+
switch (prog_type) {
case BPF_PROG_TYPE_TRACING:
case BPF_PROG_TYPE_LSM:
@@ -1941,7 +1945,10 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type,
}
}
- if (prog_fd && prog_type != BPF_PROG_TYPE_TRACING &&
+ if (attach_btf && (!btf_id || dst_prog))
+ return -EINVAL;
+
+ if (dst_prog && prog_type != BPF_PROG_TYPE_TRACING &&
prog_type != BPF_PROG_TYPE_EXT)
return -EINVAL;
@@ -2058,7 +2065,8 @@ static bool is_perfmon_prog_type(enum bpf_prog_type prog_type)
static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
{
enum bpf_prog_type type = attr->prog_type;
- struct bpf_prog *prog;
+ struct bpf_prog *prog, *dst_prog = NULL;
+ struct btf *attach_btf = NULL;
int err;
char license[128];
bool is_gpl;
@@ -2100,44 +2108,56 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
if (is_perfmon_prog_type(type) && !perfmon_capable())
return -EPERM;
+ /* attach_prog_fd/attach_btf_obj_fd can specify fd of either bpf_prog
+ * or btf, we need to check which one it is
+ */
+ if (attr->attach_prog_fd) {
+ dst_prog = bpf_prog_get(attr->attach_prog_fd);
+ if (IS_ERR(dst_prog)) {
+ dst_prog = NULL;
+ attach_btf = btf_get_by_fd(attr->attach_btf_obj_fd);
+ if (IS_ERR(attach_btf))
+ return -EINVAL;
+ if (!btf_is_kernel(attach_btf)) {
+ btf_put(attach_btf);
+ return -EINVAL;
+ }
+ }
+ } else if (attr->attach_btf_id) {
+ /* fall back to vmlinux BTF, if BTF type ID is specified */
+ attach_btf = bpf_get_btf_vmlinux();
+ if (IS_ERR(attach_btf))
+ return PTR_ERR(attach_btf);
+ if (!attach_btf)
+ return -EINVAL;
+ btf_get(attach_btf);
+ }
+
bpf_prog_load_fixup_attach_type(attr);
if (bpf_prog_load_check_attach(type, attr->expected_attach_type,
- attr->attach_btf_id,
- attr->attach_prog_fd))
+ attach_btf, attr->attach_btf_id,
+ dst_prog)) {
+ if (dst_prog)
+ bpf_prog_put(dst_prog);
+ if (attach_btf)
+ btf_put(attach_btf);
return -EINVAL;
+ }
/* plain bpf_prog allocation */
prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
- if (!prog)
+ if (!prog) {
+ if (dst_prog)
+ bpf_prog_put(dst_prog);
+ if (attach_btf)
+ btf_put(attach_btf);
return -ENOMEM;
+ }
prog->expected_attach_type = attr->expected_attach_type;
+ prog->aux->attach_btf = attach_btf;
prog->aux->attach_btf_id = attr->attach_btf_id;
-
- if (attr->attach_btf_id && !attr->attach_prog_fd) {
- struct btf *btf;
-
- btf = bpf_get_btf_vmlinux();
- if (IS_ERR(btf))
- return PTR_ERR(btf);
- if (!btf)
- return -EINVAL;
-
- btf_get(btf);
- prog->aux->attach_btf = btf;
- }
-
- if (attr->attach_prog_fd) {
- struct bpf_prog *dst_prog;
-
- dst_prog = bpf_prog_get(attr->attach_prog_fd);
- if (IS_ERR(dst_prog)) {
- err = PTR_ERR(dst_prog);
- goto free_prog;
- }
- prog->aux->dst_prog = dst_prog;
- }
-
+ prog->aux->dst_prog = dst_prog;
prog->aux->offload_requested = !!attr->prog_ifindex;
prog->aux->sleepable = attr->prog_flags & BPF_F_SLEEPABLE;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index c3458ec1f30a..1233f14f659f 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -557,7 +557,12 @@ union bpf_attr {
__aligned_u64 line_info; /* line info */
__u32 line_info_cnt; /* number of bpf_line_info records */
__u32 attach_btf_id; /* in-kernel BTF type id to attach to */
- __u32 attach_prog_fd; /* 0 to attach to vmlinux */
+ union {
+ /* valid prog_fd to attach to bpf prog */
+ __u32 attach_prog_fd;
+ /* or valid module BTF object fd or 0 to attach to vmlinux */
+ __u32 attach_btf_obj_fd;
+ };
};
struct { /* anonymous struct used by BPF_OBJ_* commands */
--
2.24.1
