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bpf: Allow to specify kernel module BTFs when attaching BPF programs

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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@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20201203204634.1325171-11-andrii@kernel.org
This commit is contained in:
Andrii Nakryiko 2020-12-03 12:46:30 -08:00 committed by Alexei Starovoitov
parent 22dc4a0f5e
commit 290248a5b7
5 changed files with 69 additions and 33 deletions
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1
include/linux/btf.h
View file

@ -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);

7
include/uapi/linux/bpf.h
View file

@ -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 */

5
kernel/bpf/btf.c
View file

@ -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;

82
kernel/bpf/syscall.c
View file

@ -1926,12 +1926,16 @@ 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:
@ -1943,7 +1947,10 @@ 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;
@ -2060,7 +2067,8 @@ 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;
@ -2102,44 +2110,56 @@ 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;

7
tools/include/uapi/linux/bpf.h
View file

@ -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 */