eBPF programs are safe run-to-completion functions with load/unload
methods from userspace similar to kernel modules.
User space API:
- load eBPF program
fd = bpf_prog_load(bpf_prog_type, struct nlattr *prog, int len)
where 'prog' is a sequence of sections (TEXT, LICENSE)
TEXT - array of eBPF instructions
LICENSE - must be GPL compatible to call helper functions marked gpl_only
- unload eBPF program
close(fd)
User space example of syscall(__NR_bpf, BPF_PROG_LOAD, prog_type, ...)
follows in later patches
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>
---
include/linux/bpf.h | 36 +++++++++
include/linux/filter.h | 9 ++-
include/uapi/linux/bpf.h | 28 +++++++
kernel/bpf/syscall.c | 196 ++++++++++++++++++++++++++++++++++++++++++++++
net/core/filter.c | 2 +
5 files changed, 269 insertions(+), 2 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index fd1ac4b5ba8b..ac6320f44812 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -47,4 +47,40 @@ 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_info {
+ 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;
+
+void bpf_prog_put(struct bpf_prog *prog);
+struct bpf_prog *bpf_prog_get(u32 ufd);
+
#endif /* _LINUX_BPF_H */
diff --git a/include/linux/filter.h b/include/linux/filter.h
index f04793474d16..f06913b29861 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -31,11 +31,16 @@ struct sock_fprog_kern {
struct sk_buff;
struct sock;
struct seccomp_data;
+struct bpf_prog_info;
struct bpf_prog {
u32 jited:1, /* Is our filter JIT'ed? */
- len:31; /* Number of filter blocks */
- struct sock_fprog_kern *orig_prog; /* Original BPF program */
+ has_info:1, /* whether 'info' is valid */
+ len:30; /* Number of filter blocks */
+ union {
+ struct sock_fprog_kern *orig_prog; /* Original BPF program */
+ struct bpf_prog_info *info;
+ };
unsigned int (*bpf_func)(const struct sk_buff *skb,
const struct bpf_insn *filter);
union {
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 828e873fa435..aa09ba084ebc 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -344,6 +344,13 @@ enum bpf_cmd {
* returns zero and stores next key or negative error
*/
BPF_MAP_GET_NEXT_KEY,
+
+ /* verify and load eBPF program
+ * prog_id = bpf_prog_load(bpf_prog_type, struct nlattr *prog, int len)
+ * prog is a sequence of sections
+ * returns fd or negative error
+ */
+ BPF_PROG_LOAD,
};
enum bpf_map_attributes {
@@ -361,4 +368,25 @@ enum bpf_map_type {
BPF_MAP_TYPE_HASH,
};
+enum bpf_prog_attributes {
+ BPF_PROG_UNSPEC,
+ BPF_PROG_TEXT, /* array of eBPF instructions */
+ BPF_PROG_LICENSE, /* license string */
+ __BPF_PROG_ATTR_MAX,
+};
+#define BPF_PROG_ATTR_MAX (__BPF_PROG_ATTR_MAX - 1)
+#define BPF_PROG_MAX_ATTR_SIZE 65535
+
+enum bpf_prog_type {
+ BPF_PROG_TYPE_UNSPEC,
+};
+
+/* 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__ */
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 45e100ece1b7..4c5f5169f6fc 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -14,6 +14,8 @@
#include <net/netlink.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
+#include <linux/license.h>
+#include <linux/filter.h>
static LIST_HEAD(bpf_map_types);
@@ -315,6 +317,197 @@ 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->info->ops = tl->ops;
+ prog->info->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_bpf_prog_info(struct bpf_prog_info *info)
+{
+ int i;
+
+ for (i = 0; i < info->used_map_cnt; i++)
+ bpf_map_put(info->used_maps[i]);
+
+ kfree(info->used_maps);
+ kfree(info);
+}
+
+void bpf_prog_put(struct bpf_prog *prog)
+{
+ BUG_ON(!prog->has_info);
+ if (atomic_dec_and_test(&prog->info->refcnt)) {
+ free_bpf_prog_info(prog->info);
+ 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->info->refcnt);
+ fdput(f);
+ return prog;
+}
+
+static const struct nla_policy prog_policy[BPF_PROG_ATTR_MAX + 1] = {
+ [BPF_PROG_TEXT] = { .type = NLA_BINARY },
+ [BPF_PROG_LICENSE] = { .type = NLA_NUL_STRING },
+};
+
+static int bpf_prog_load(enum bpf_prog_type type, struct nlattr __user *uattr,
+ int len)
+{
+ struct nlattr *tb[BPF_PROG_ATTR_MAX + 1];
+ struct bpf_prog *prog;
+ struct nlattr *attr;
+ size_t insn_len;
+ int err;
+ bool is_gpl;
+
+ if (len <= 0 || len > BPF_PROG_MAX_ATTR_SIZE)
+ return -EINVAL;
+
+ attr = kmalloc(len, GFP_USER);
+ if (!attr)
+ return -ENOMEM;
+
+ /* copy eBPF program from user space */
+ err = -EFAULT;
+ if (copy_from_user(attr, uattr, len) != 0)
+ goto free_attr;
+
+ /* perform basic validation */
+ err = nla_parse(tb, BPF_PROG_ATTR_MAX, attr, len, prog_policy);
+ if (err < 0)
+ goto free_attr;
+
+ err = -EINVAL;
+ /* look for mandatory license string */
+ if (!tb[BPF_PROG_LICENSE])
+ goto free_attr;
+
+ /* eBPF programs must be GPL compatible to use GPL-ed functions */
+ is_gpl = license_is_gpl_compatible(nla_data(tb[BPF_PROG_LICENSE]));
+
+ /* look for mandatory array of eBPF instructions */
+ if (!tb[BPF_PROG_TEXT])
+ goto free_attr;
+
+ insn_len = nla_len(tb[BPF_PROG_TEXT]);
+ if (insn_len % sizeof(struct bpf_insn) != 0 || insn_len <= 0)
+ goto free_attr;
+
+ /* plain bpf_prog allocation */
+ err = -ENOMEM;
+ prog = kmalloc(bpf_prog_size(insn_len), GFP_USER);
+ if (!prog)
+ goto free_attr;
+
+ prog->len = insn_len / sizeof(struct bpf_insn);
+ memcpy(prog->insns, nla_data(tb[BPF_PROG_TEXT]), insn_len);
+ prog->orig_prog = NULL;
+ prog->jited = 0;
+ prog->has_info = 0;
+
+ /* allocate eBPF related auxilary data */
+ prog->info = kzalloc(sizeof(struct bpf_prog_info), GFP_USER);
+ if (!prog->info)
+ goto free_prog;
+ prog->has_info = 1;
+ atomic_set(&prog->info->refcnt, 1);
+ prog->info->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_info;
+
+ /* run eBPF verifier */
+ /* err = bpf_check(prog, tb); */
+
+ if (err < 0)
+ goto free_prog_info;
+
+ /* 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_prog_info;
+
+ /* user supplied eBPF prog attributes are no longer needed */
+ kfree(attr);
+
+ return err;
+
+free_prog_info:
+ free_bpf_prog_info(prog->info);
+free_prog:
+ bpf_prog_free(prog);
+free_attr:
+ kfree(attr);
+ return err;
+}
+
SYSCALL_DEFINE5(bpf, int, cmd, unsigned long, arg2, unsigned long, arg3,
unsigned long, arg4, unsigned long, arg5)
{
@@ -348,6 +541,9 @@ SYSCALL_DEFINE5(bpf, int, cmd, unsigned long, arg2, unsigned long, arg3,
case BPF_MAP_GET_NEXT_KEY:
return map_get_next_key((int) arg2, (void __user *) arg3,
(void __user *) arg4);
+ case BPF_PROG_LOAD:
+ return bpf_prog_load((enum bpf_prog_type) arg2,
+ (struct nlattr __user *) arg3, (int) arg4);
default:
return -EINVAL;
}
diff --git a/net/core/filter.c b/net/core/filter.c
index d814b8a89d0f..ed15874a9beb 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -835,6 +835,7 @@ static void bpf_release_orig_filter(struct bpf_prog *fp)
{
struct sock_fprog_kern *fprog = fp->orig_prog;
+ BUG_ON(fp->has_info);
if (fprog) {
kfree(fprog->filter);
kfree(fprog);
@@ -973,6 +974,7 @@ static struct bpf_prog *bpf_prepare_filter(struct bpf_prog *fp)
fp->bpf_func = NULL;
fp->jited = 0;
+ fp->has_info = 0;
err = bpf_check_classic(fp->insns, fp->len);
if (err) {
--
1.7.9.5
--
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