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Commit f56a653c authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Daniel Borkmann
Browse files

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: default avatarMartin KaFai Lau <kafai@fb.com>
Acked-by: default avatarAlexei Starovoitov <ast@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent b00b8dae

include/linux/btf.h

+4 −0
Original line number Diff line number Diff line
@@ -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.

 *

include/uapi/linux/bpf.h

+9 −0
Original line number Diff line number Diff line
@@ -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:

kernel/bpf/btf.c

+67 −0
Original line number Diff line number Diff line
@@ -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;

}

kernel/bpf/syscall.c

+17 −0
Original line number Diff line number Diff line
@@ -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;