bpf: btf: Add BPF_BTF_LOAD command

This patch adds a BPF_BTF_LOAD command which
1) loads and verifies the BTF (implemented in earlier patches)
2) returns a BTF fd to userspace.  In the next patch, the
   BTF fd can be specified during BPF_MAP_CREATE.

It currently limits to CAP_SYS_ADMIN.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Martin KaFai Lau 2018-04-18 15:56:01 -07:00 committed by Daniel Borkmann
parent b00b8daec8
commit f56a653c1f
4 changed files with 97 additions and 0 deletions

View File

@ -8,7 +8,11 @@
struct btf;
struct btf_type;
union bpf_attr;
void btf_put(struct btf *btf);
int btf_new_fd(const union bpf_attr *attr);
struct btf *btf_get_by_fd(int fd);
/* Figure out the size of a type_id. If type_id is a modifier
* (e.g. const), it will be resolved to find out the type with size.
*

View File

@ -95,6 +95,7 @@ enum bpf_cmd {
BPF_OBJ_GET_INFO_BY_FD,
BPF_PROG_QUERY,
BPF_RAW_TRACEPOINT_OPEN,
BPF_BTF_LOAD,
};
enum bpf_map_type {
@ -363,6 +364,14 @@ union bpf_attr {
__u64 name;
__u32 prog_fd;
} raw_tracepoint;
struct { /* anonymous struct for BPF_BTF_LOAD */
__aligned_u64 btf;
__aligned_u64 btf_log_buf;
__u32 btf_size;
__u32 btf_log_size;
__u32 btf_log_level;
};
} __attribute__((aligned(8)));
/* BPF helper function descriptions:

View File

@ -7,6 +7,8 @@
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/bpf_verifier.h>
@ -190,6 +192,7 @@ struct btf {
u32 nr_types;
u32 types_size;
u32 data_size;
refcount_t refcnt;
};
enum verifier_phase {
@ -604,6 +607,17 @@ static void btf_free(struct btf *btf)
kfree(btf);
}
static void btf_get(struct btf *btf)
{
refcount_inc(&btf->refcnt);
}
void btf_put(struct btf *btf)
{
if (btf && refcount_dec_and_test(&btf->refcnt))
btf_free(btf);
}
static int env_resolve_init(struct btf_verifier_env *env)
{
struct btf *btf = env->btf;
@ -1963,6 +1977,7 @@ static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size,
if (!err) {
btf_verifier_env_free(env);
btf_get(btf);
return btf;
}
@ -1980,3 +1995,55 @@ void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
btf_type_ops(t)->seq_show(btf, t, type_id, obj, 0, m);
}
static int btf_release(struct inode *inode, struct file *filp)
{
btf_put(filp->private_data);
return 0;
}
static const struct file_operations btf_fops = {
.release = btf_release,
};
int btf_new_fd(const union bpf_attr *attr)
{
struct btf *btf;
int fd;
btf = btf_parse(u64_to_user_ptr(attr->btf),
attr->btf_size, attr->btf_log_level,
u64_to_user_ptr(attr->btf_log_buf),
attr->btf_log_size);
if (IS_ERR(btf))
return PTR_ERR(btf);
fd = anon_inode_getfd("btf", &btf_fops, btf,
O_RDONLY | O_CLOEXEC);
if (fd < 0)
btf_put(btf);
return fd;
}
struct btf *btf_get_by_fd(int fd)
{
struct btf *btf;
struct fd f;
f = fdget(fd);
if (!f.file)
return ERR_PTR(-EBADF);
if (f.file->f_op != &btf_fops) {
fdput(f);
return ERR_PTR(-EINVAL);
}
btf = f.file->private_data;
btf_get(btf);
fdput(f);
return btf;
}

View File

@ -11,6 +11,7 @@
*/
#include <linux/bpf.h>
#include <linux/bpf_trace.h>
#include <linux/btf.h>
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
@ -2023,6 +2024,19 @@ static int bpf_obj_get_info_by_fd(const union bpf_attr *attr,
return err;
}
#define BPF_BTF_LOAD_LAST_FIELD btf_log_level
static int bpf_btf_load(const union bpf_attr *attr)
{
if (CHECK_ATTR(BPF_BTF_LOAD))
return -EINVAL;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
return btf_new_fd(attr);
}
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{
union bpf_attr attr = {};
@ -2103,6 +2117,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_RAW_TRACEPOINT_OPEN:
err = bpf_raw_tracepoint_open(&attr);
break;
case BPF_BTF_LOAD:
err = bpf_btf_load(&attr);
break;
default:
err = -EINVAL;
break;