Commit fcc2c1fb authored by Kui-Feng Lee's avatar Kui-Feng Lee Committed by Martin KaFai Lau
Browse files

bpf: pass attached BTF to the bpf_struct_ops subsystem 



Pass the fd of a btf from the userspace to the bpf() syscall, and then
convert the fd into a btf. The btf is generated from the module that
defines the target BPF struct_ops type.

In order to inform the kernel about the module that defines the target
struct_ops type, the userspace program needs to provide a btf fd for the
respective module's btf. This btf contains essential information on the
types defined within the module, including the target struct_ops type.

A btf fd must be provided to the kernel for struct_ops maps and for the bpf
programs attached to those maps.

In the case of the bpf programs, the attach_btf_obj_fd parameter is passed
as part of the bpf_attr and is converted into a btf. This btf is then
stored in the prog->aux->attach_btf field. Here, it just let the verifier
access attach_btf directly.

In the case of struct_ops maps, a btf fd is passed as value_type_btf_obj_fd
of bpf_attr. The bpf_struct_ops_map_alloc() function converts the fd to a
btf and stores it as st_map->btf. A flag BPF_F_VTYPE_BTF_OBJ_FD is added
for map_flags to indicate that the value of value_type_btf_obj_fd is set.

Signed-off-by: default avatarKui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240119225005.668602-9-thinker.li@gmail.com


Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
parent 689423db

include/uapi/linux/bpf.h

+8 −0
Original line number Diff line number Diff line
@@ -1330,6 +1330,9 @@ enum { 


/* Get path from provided FD in BPF_OBJ_PIN/BPF_OBJ_GET commands */

	BPF_F_PATH_FD		= (1U << 14),



/* Flag for value_type_btf_obj_fd, the fd is available */

	BPF_F_VTYPE_BTF_OBJ_FD	= (1U << 15),

};



/* Flags for BPF_PROG_QUERY. */
@@ -1403,6 +1406,11 @@ union bpf_attr { 
		 * to using 5 hash functions).

		 */

		__u64	map_extra;



		__s32   value_type_btf_obj_fd;	/* fd pointing to a BTF

						 * type data for

						 * btf_vmlinux_value_type_id.

						 */

	};



	struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */

kernel/bpf/bpf_struct_ops.c

+47 −18
Original line number Diff line number Diff line
@@ -641,6 +641,7 @@ static void __bpf_struct_ops_map_free(struct bpf_map *map) 
		bpf_jit_uncharge_modmem(PAGE_SIZE);

	}

	bpf_map_area_free(st_map->uvalue);

	btf_put(st_map->btf);

	bpf_map_area_free(st_map);

}
@@ -669,7 +670,8 @@ static void bpf_struct_ops_map_free(struct bpf_map *map) 
static int bpf_struct_ops_map_alloc_check(union bpf_attr *attr)

{

	if (attr->key_size != sizeof(unsigned int) || attr->max_entries != 1 ||

	    (attr->map_flags & ~BPF_F_LINK) || !attr->btf_vmlinux_value_type_id)

	    (attr->map_flags & ~(BPF_F_LINK | BPF_F_VTYPE_BTF_OBJ_FD)) ||

	    !attr->btf_vmlinux_value_type_id)

		return -EINVAL;

	return 0;

}
@@ -681,15 +683,36 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) 
	struct bpf_struct_ops_map *st_map;

	const struct btf_type *t, *vt;

	struct bpf_map *map;

	struct btf *btf;

	int ret;



	st_ops_desc = bpf_struct_ops_find_value(btf_vmlinux, attr->btf_vmlinux_value_type_id);

	if (!st_ops_desc)

		return ERR_PTR(-ENOTSUPP);

	if (attr->map_flags & BPF_F_VTYPE_BTF_OBJ_FD) {

		/* The map holds btf for its whole life time. */

		btf = btf_get_by_fd(attr->value_type_btf_obj_fd);

		if (IS_ERR(btf))

			return ERR_CAST(btf);

		if (!btf_is_module(btf)) {

			btf_put(btf);

			return ERR_PTR(-EINVAL);

		}

	} else {

		btf = bpf_get_btf_vmlinux();

		if (IS_ERR(btf))

			return ERR_CAST(btf);

		btf_get(btf);

	}



	st_ops_desc = bpf_struct_ops_find_value(btf, attr->btf_vmlinux_value_type_id);

	if (!st_ops_desc) {

		ret = -ENOTSUPP;

		goto errout;

	}



	vt = st_ops_desc->value_type;

	if (attr->value_size != vt->size)

		return ERR_PTR(-EINVAL);

	if (attr->value_size != vt->size) {

		ret = -EINVAL;

		goto errout;

	}



	t = st_ops_desc->type;
@@ -700,17 +723,17 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) 
		(vt->size - sizeof(struct bpf_struct_ops_value));



	st_map = bpf_map_area_alloc(st_map_size, NUMA_NO_NODE);

	if (!st_map)

		return ERR_PTR(-ENOMEM);

	if (!st_map) {

		ret = -ENOMEM;

		goto errout;

	}



	st_map->st_ops_desc = st_ops_desc;

	map = &st_map->map;



	ret = bpf_jit_charge_modmem(PAGE_SIZE);

	if (ret) {

		__bpf_struct_ops_map_free(map);

		return ERR_PTR(ret);

	}

	if (ret)

		goto errout_free;



	st_map->image = arch_alloc_bpf_trampoline(PAGE_SIZE);

	if (!st_map->image) {
@@ -719,24 +742,30 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr) 
		 * here.

		 */

		bpf_jit_uncharge_modmem(PAGE_SIZE);

		__bpf_struct_ops_map_free(map);

		return ERR_PTR(-ENOMEM);

		ret = -ENOMEM;

		goto errout_free;

	}

	st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);

	st_map->links =

		bpf_map_area_alloc(btf_type_vlen(t) * sizeof(struct bpf_links *),

				   NUMA_NO_NODE);

	if (!st_map->uvalue || !st_map->links) {

		__bpf_struct_ops_map_free(map);

		return ERR_PTR(-ENOMEM);

		ret = -ENOMEM;

		goto errout_free;

	}



	st_map->btf = btf_vmlinux;

	st_map->btf = btf;



	mutex_init(&st_map->lock);

	bpf_map_init_from_attr(map, attr);



	return map;



errout_free:

	__bpf_struct_ops_map_free(map);

errout:

	btf_put(btf);



	return ERR_PTR(ret);

}



static u64 bpf_struct_ops_map_mem_usage(const struct bpf_map *map)

kernel/bpf/syscall.c

+1 −1
Original line number Diff line number Diff line
@@ -1123,7 +1123,7 @@ static int map_check_btf(struct bpf_map *map, const struct btf *btf, 
	return ret;

}



#define BPF_MAP_CREATE_LAST_FIELD map_extra

#define BPF_MAP_CREATE_LAST_FIELD value_type_btf_obj_fd

/* called via syscall */

static int map_create(union bpf_attr *attr)

{

kernel/bpf/verifier.c

+6 −3
Original line number Diff line number Diff line
@@ -20290,6 +20290,7 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env) 
	const struct btf_member *member;

	struct bpf_prog *prog = env->prog;

	u32 btf_id, member_idx;

	struct btf *btf;

	const char *mname;









	if (!prog->gpl_compatible) {








@@ -20297,8 +20298,10 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)







		return -EINVAL;









	}

















	btf = prog->aux->attach_btf ?: bpf_get_btf_vmlinux();

















	btf_id = prog->aux->attach_btf_id;









	st_ops_desc = bpf_struct_ops_find(btf_vmlinux, btf_id);









	st_ops_desc = bpf_struct_ops_find(btf, btf_id);









	if (!st_ops_desc) {









		verbose(env, "attach_btf_id %u is not a supported struct\n",









			btf_id);








@@ -20315,8 +20318,8 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)







	}

















	member = &btf_type_member(t)[member_idx];









	mname = btf_name_by_offset(btf_vmlinux, member->name_off);









	func_proto = btf_type_resolve_func_ptr(btf_vmlinux, member->type,









	mname = btf_name_by_offset(btf, member->name_off);









	func_proto = btf_type_resolve_func_ptr(btf, member->type,









					       NULL);









	if (!func_proto) {









		verbose(env, "attach to invalid member %s(@idx %u) of struct %s\n",

























tools/include/uapi/linux/bpf.h



+8
−0






























Original line number
Diff line number
Diff line







@@ -1330,6 +1330,9 @@ enum {

















/* Get path from provided FD in BPF_OBJ_PIN/BPF_OBJ_GET commands */









	BPF_F_PATH_FD		= (1U << 14),



















/* Flag for value_type_btf_obj_fd, the fd is available */









	BPF_F_VTYPE_BTF_OBJ_FD	= (1U << 15),









};



















/* Flags for BPF_PROG_QUERY. */








@@ -1403,6 +1406,11 @@ union bpf_attr {







		 * to using 5 hash functions).









		 */









		__u64	map_extra;



















		__s32   value_type_btf_obj_fd;	/* fd pointing to a BTF









						 * type data for









						 * btf_vmlinux_value_type_id.









						 */









	};



















	struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */