bpf: expand BPF syscall with program load/unload

eBPF programs are similar to kernel modules. They are loaded by the user
process and automatically unloaded when process exits. Each eBPF program is
a safe run-to-completion set of instructions. eBPF verifier statically
determines that the program terminates and is safe to execute.

The following syscall wrapper can be used to load the program:
int bpf_prog_load(enum bpf_prog_type prog_type,
                  const struct bpf_insn *insns, int insn_cnt,
                  const char *license)
{
    union bpf_attr attr = {
        .prog_type = prog_type,
        .insns = ptr_to_u64(insns),
        .insn_cnt = insn_cnt,
        .license = ptr_to_u64(license),
    };

    return bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
}
where 'insns' is an array of eBPF instructions and 'license' is a string
that must be GPL compatible to call helper functions marked gpl_only

Upon succesful load the syscall returns prog_fd.
Use close(prog_fd) to unload the program.

User space tests and examples follow in the later patches

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov 2014-09-26 00:17:00 -07:00 committed by David S. Miller
parent db20fd2b01
commit 09756af468
5 changed files with 246 additions and 20 deletions

View File

@ -46,4 +46,42 @@ void bpf_register_map_type(struct bpf_map_type_list *tl);
void bpf_map_put(struct bpf_map *map);
struct bpf_map *bpf_map_get(struct fd f);
/* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
* to in-kernel helper functions and for adjusting imm32 field in BPF_CALL
* instructions after verifying
*/
struct bpf_func_proto {
u64 (*func)(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);
bool gpl_only;
};
struct bpf_verifier_ops {
/* return eBPF function prototype for verification */
const struct bpf_func_proto *(*get_func_proto)(enum bpf_func_id func_id);
};
struct bpf_prog_type_list {
struct list_head list_node;
struct bpf_verifier_ops *ops;
enum bpf_prog_type type;
};
void bpf_register_prog_type(struct bpf_prog_type_list *tl);
struct bpf_prog;
struct bpf_prog_aux {
atomic_t refcnt;
bool is_gpl_compatible;
enum bpf_prog_type prog_type;
struct bpf_verifier_ops *ops;
struct bpf_map **used_maps;
u32 used_map_cnt;
struct bpf_prog *prog;
struct work_struct work;
};
void bpf_prog_put(struct bpf_prog *prog);
struct bpf_prog *bpf_prog_get(u32 ufd);
#endif /* _LINUX_BPF_H */

View File

@ -21,6 +21,7 @@
struct sk_buff;
struct sock;
struct seccomp_data;
struct bpf_prog_aux;
/* ArgX, context and stack frame pointer register positions. Note,
* Arg1, Arg2, Arg3, etc are used as argument mappings of function
@ -300,17 +301,12 @@ struct bpf_binary_header {
u8 image[];
};
struct bpf_work_struct {
struct bpf_prog *prog;
struct work_struct work;
};
struct bpf_prog {
u16 pages; /* Number of allocated pages */
bool jited; /* Is our filter JIT'ed? */
u32 len; /* Number of filter blocks */
struct sock_fprog_kern *orig_prog; /* Original BPF program */
struct bpf_work_struct *work; /* Deferred free work struct */
struct bpf_prog_aux *aux; /* Auxiliary fields */
unsigned int (*bpf_func)(const struct sk_buff *skb,
const struct bpf_insn *filter);
/* Instructions for interpreter */

View File

@ -99,12 +99,23 @@ enum bpf_cmd {
* returns zero and stores next key or negative error
*/
BPF_MAP_GET_NEXT_KEY,
/* verify and load eBPF program
* prog_fd = bpf(BPF_PROG_LOAD, union bpf_attr *attr, u32 size)
* Using attr->prog_type, attr->insns, attr->license
* returns fd or negative error
*/
BPF_PROG_LOAD,
};
enum bpf_map_type {
BPF_MAP_TYPE_UNSPEC,
};
enum bpf_prog_type {
BPF_PROG_TYPE_UNSPEC,
};
union bpf_attr {
struct { /* anonymous struct used by BPF_MAP_CREATE command */
__u32 map_type; /* one of enum bpf_map_type */
@ -121,6 +132,21 @@ union bpf_attr {
__aligned_u64 next_key;
};
};
struct { /* anonymous struct used by BPF_PROG_LOAD command */
__u32 prog_type; /* one of enum bpf_prog_type */
__u32 insn_cnt;
__aligned_u64 insns;
__aligned_u64 license;
};
} __attribute__((aligned(8)));
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
* function eBPF program intends to call
*/
enum bpf_func_id {
BPF_FUNC_unspec,
__BPF_FUNC_MAX_ID,
};
#endif /* _UAPI__LINUX_BPF_H__ */

View File

@ -27,6 +27,7 @@
#include <linux/random.h>
#include <linux/moduleloader.h>
#include <asm/unaligned.h>
#include <linux/bpf.h>
/* Registers */
#define BPF_R0 regs[BPF_REG_0]
@ -71,7 +72,7 @@ struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)
{
gfp_t gfp_flags = GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO |
gfp_extra_flags;
struct bpf_work_struct *ws;
struct bpf_prog_aux *aux;
struct bpf_prog *fp;
size = round_up(size, PAGE_SIZE);
@ -79,14 +80,14 @@ struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags)
if (fp == NULL)
return NULL;
ws = kmalloc(sizeof(*ws), GFP_KERNEL | gfp_extra_flags);
if (ws == NULL) {
aux = kzalloc(sizeof(*aux), GFP_KERNEL | gfp_extra_flags);
if (aux == NULL) {
vfree(fp);
return NULL;
}
fp->pages = size / PAGE_SIZE;
fp->work = ws;
fp->aux = aux;
return fp;
}
@ -110,10 +111,10 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
memcpy(fp, fp_old, fp_old->pages * PAGE_SIZE);
fp->pages = size / PAGE_SIZE;
/* We keep fp->work from fp_old around in the new
/* We keep fp->aux from fp_old around in the new
* reallocated structure.
*/
fp_old->work = NULL;
fp_old->aux = NULL;
__bpf_prog_free(fp_old);
}
@ -123,7 +124,7 @@ EXPORT_SYMBOL_GPL(bpf_prog_realloc);
void __bpf_prog_free(struct bpf_prog *fp)
{
kfree(fp->work);
kfree(fp->aux);
vfree(fp);
}
EXPORT_SYMBOL_GPL(__bpf_prog_free);
@ -638,19 +639,19 @@ EXPORT_SYMBOL_GPL(bpf_prog_select_runtime);
static void bpf_prog_free_deferred(struct work_struct *work)
{
struct bpf_work_struct *ws;
struct bpf_prog_aux *aux;
ws = container_of(work, struct bpf_work_struct, work);
bpf_jit_free(ws->prog);
aux = container_of(work, struct bpf_prog_aux, work);
bpf_jit_free(aux->prog);
}
/* Free internal BPF program */
void bpf_prog_free(struct bpf_prog *fp)
{
struct bpf_work_struct *ws = fp->work;
struct bpf_prog_aux *aux = fp->aux;
INIT_WORK(&ws->work, bpf_prog_free_deferred);
ws->prog = fp;
schedule_work(&ws->work);
INIT_WORK(&aux->work, bpf_prog_free_deferred);
aux->prog = fp;
schedule_work(&aux->work);
}
EXPORT_SYMBOL_GPL(bpf_prog_free);

View File

@ -14,6 +14,8 @@
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/license.h>
#include <linux/filter.h>
static LIST_HEAD(bpf_map_types);
@ -334,6 +336,166 @@ err_put:
return err;
}
static LIST_HEAD(bpf_prog_types);
static int find_prog_type(enum bpf_prog_type type, struct bpf_prog *prog)
{
struct bpf_prog_type_list *tl;
list_for_each_entry(tl, &bpf_prog_types, list_node) {
if (tl->type == type) {
prog->aux->ops = tl->ops;
prog->aux->prog_type = type;
return 0;
}
}
return -EINVAL;
}
void bpf_register_prog_type(struct bpf_prog_type_list *tl)
{
list_add(&tl->list_node, &bpf_prog_types);
}
/* drop refcnt on maps used by eBPF program and free auxilary data */
static void free_used_maps(struct bpf_prog_aux *aux)
{
int i;
for (i = 0; i < aux->used_map_cnt; i++)
bpf_map_put(aux->used_maps[i]);
kfree(aux->used_maps);
}
void bpf_prog_put(struct bpf_prog *prog)
{
if (atomic_dec_and_test(&prog->aux->refcnt)) {
free_used_maps(prog->aux);
bpf_prog_free(prog);
}
}
static int bpf_prog_release(struct inode *inode, struct file *filp)
{
struct bpf_prog *prog = filp->private_data;
bpf_prog_put(prog);
return 0;
}
static const struct file_operations bpf_prog_fops = {
.release = bpf_prog_release,
};
static struct bpf_prog *get_prog(struct fd f)
{
struct bpf_prog *prog;
if (!f.file)
return ERR_PTR(-EBADF);
if (f.file->f_op != &bpf_prog_fops) {
fdput(f);
return ERR_PTR(-EINVAL);
}
prog = f.file->private_data;
return prog;
}
/* called by sockets/tracing/seccomp before attaching program to an event
* pairs with bpf_prog_put()
*/
struct bpf_prog *bpf_prog_get(u32 ufd)
{
struct fd f = fdget(ufd);
struct bpf_prog *prog;
prog = get_prog(f);
if (IS_ERR(prog))
return prog;
atomic_inc(&prog->aux->refcnt);
fdput(f);
return prog;
}
/* last field in 'union bpf_attr' used by this command */
#define BPF_PROG_LOAD_LAST_FIELD license
static int bpf_prog_load(union bpf_attr *attr)
{
enum bpf_prog_type type = attr->prog_type;
struct bpf_prog *prog;
int err;
char license[128];
bool is_gpl;
if (CHECK_ATTR(BPF_PROG_LOAD))
return -EINVAL;
/* copy eBPF program license from user space */
if (strncpy_from_user(license, u64_to_ptr(attr->license),
sizeof(license) - 1) < 0)
return -EFAULT;
license[sizeof(license) - 1] = 0;
/* eBPF programs must be GPL compatible to use GPL-ed functions */
is_gpl = license_is_gpl_compatible(license);
if (attr->insn_cnt >= BPF_MAXINSNS)
return -EINVAL;
/* plain bpf_prog allocation */
prog = bpf_prog_alloc(bpf_prog_size(attr->insn_cnt), GFP_USER);
if (!prog)
return -ENOMEM;
prog->len = attr->insn_cnt;
err = -EFAULT;
if (copy_from_user(prog->insns, u64_to_ptr(attr->insns),
prog->len * sizeof(struct bpf_insn)) != 0)
goto free_prog;
prog->orig_prog = NULL;
prog->jited = false;
atomic_set(&prog->aux->refcnt, 1);
prog->aux->is_gpl_compatible = is_gpl;
/* find program type: socket_filter vs tracing_filter */
err = find_prog_type(type, prog);
if (err < 0)
goto free_prog;
/* run eBPF verifier */
/* err = bpf_check(prog, tb); */
if (err < 0)
goto free_used_maps;
/* eBPF program is ready to be JITed */
bpf_prog_select_runtime(prog);
err = anon_inode_getfd("bpf-prog", &bpf_prog_fops, prog, O_RDWR | O_CLOEXEC);
if (err < 0)
/* failed to allocate fd */
goto free_used_maps;
return err;
free_used_maps:
free_used_maps(prog->aux);
free_prog:
bpf_prog_free(prog);
return err;
}
SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, size)
{
union bpf_attr attr = {};
@ -395,6 +557,9 @@ SYSCALL_DEFINE3(bpf, int, cmd, union bpf_attr __user *, uattr, unsigned int, siz
case BPF_MAP_GET_NEXT_KEY:
err = map_get_next_key(&attr);
break;
case BPF_PROG_LOAD:
err = bpf_prog_load(&attr);
break;
default:
err = -EINVAL;
break;