Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 808649fb authored by Andrey Ignatov's avatar Andrey Ignatov Committed by Alexei Starovoitov
Browse files

bpf: Introduce bpf_sysctl_get_name helper 



Add bpf_sysctl_get_name() helper to copy sysctl name (/proc/sys/ entry)
into provided by BPF_PROG_TYPE_CGROUP_SYSCTL program buffer.

By default full name (w/o /proc/sys/) is copied, e.g. "net/ipv4/tcp_mem".

If BPF_F_SYSCTL_BASE_NAME flag is set, only base name will be copied,
e.g. "tcp_mem".

Documentation for the new helper is provided in bpf.h UAPI.

Signed-off-by: default avatarAndrey Ignatov <rdna@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 7b146ceb

include/uapi/linux/bpf.h

+21 −1
Original line number Diff line number Diff line
@@ -2506,6 +2506,22 @@ union bpf_attr { 
 * 	Return

 * 		0 if iph and th are a valid SYN cookie ACK, or a negative error

 * 		otherwise.

 *

 * int bpf_sysctl_get_name(struct bpf_sysctl *ctx, char *buf, size_t buf_len, u64 flags)

 *	Description

 *		Get name of sysctl in /proc/sys/ and copy it into provided by

 *		program buffer *buf* of size *buf_len*.

 *

 *		The buffer is always NUL terminated, unless it's zero-sized.

 *

 *		If *flags* is zero, full name (e.g. "net/ipv4/tcp_mem") is

 *		copied. Use **BPF_F_SYSCTL_BASE_NAME** flag to copy base name

 *		only (e.g. "tcp_mem").

 *	Return

 *		Number of character copied (not including the trailing NUL).

 *

 *		**-E2BIG** if the buffer wasn't big enough (*buf* will contain

 *		truncated name in this case).

 */

#define __BPF_FUNC_MAPPER(FN)		\

	FN(unspec),			\
@@ -2608,7 +2624,8 @@ union bpf_attr { 
	FN(skb_ecn_set_ce),		\

	FN(get_listener_sock),		\

	FN(skc_lookup_tcp),		\

	FN(tcp_check_syncookie),

	FN(tcp_check_syncookie),	\

	FN(sysctl_get_name),



/* integer value in 'imm' field of BPF_CALL instruction selects which helper

 * function eBPF program intends to call
@@ -2681,6 +2698,9 @@ enum bpf_func_id { 
					  BPF_ADJ_ROOM_ENCAP_L2_MASK) \

					 << BPF_ADJ_ROOM_ENCAP_L2_SHIFT)



/* BPF_FUNC_sysctl_get_name flags. */

#define BPF_F_SYSCTL_BASE_NAME		(1ULL << 0)



/* Mode for BPF_FUNC_skb_adjust_room helper. */

enum bpf_adj_room_mode {

	BPF_ADJ_ROOM_NET,

kernel/bpf/cgroup.c

+69 −1
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <linux/filter.h>

#include <linux/slab.h>

#include <linux/sysctl.h>

#include <linux/string.h>

#include <linux/bpf.h>

#include <linux/bpf-cgroup.h>

#include <net/sock.h>
@@ -806,11 +807,78 @@ int __cgroup_bpf_run_filter_sysctl(struct ctl_table_header *head, 
}

EXPORT_SYMBOL(__cgroup_bpf_run_filter_sysctl);



static ssize_t sysctl_cpy_dir(const struct ctl_dir *dir, char **bufp,

			      size_t *lenp)

{

	ssize_t tmp_ret = 0, ret;



	if (dir->header.parent) {

		tmp_ret = sysctl_cpy_dir(dir->header.parent, bufp, lenp);

		if (tmp_ret < 0)

			return tmp_ret;

	}



	ret = strscpy(*bufp, dir->header.ctl_table[0].procname, *lenp);

	if (ret < 0)

		return ret;

	*bufp += ret;

	*lenp -= ret;

	ret += tmp_ret;



	/* Avoid leading slash. */

	if (!ret)

		return ret;



	tmp_ret = strscpy(*bufp, "/", *lenp);

	if (tmp_ret < 0)

		return tmp_ret;

	*bufp += tmp_ret;

	*lenp -= tmp_ret;



	return ret + tmp_ret;

}



BPF_CALL_4(bpf_sysctl_get_name, struct bpf_sysctl_kern *, ctx, char *, buf,

	   size_t, buf_len, u64, flags)

{

	ssize_t tmp_ret = 0, ret;



	if (!buf)

		return -EINVAL;



	if (!(flags & BPF_F_SYSCTL_BASE_NAME)) {

		if (!ctx->head)

			return -EINVAL;

		tmp_ret = sysctl_cpy_dir(ctx->head->parent, &buf, &buf_len);

		if (tmp_ret < 0)

			return tmp_ret;

	}



	ret = strscpy(buf, ctx->table->procname, buf_len);



	return ret < 0 ? ret : tmp_ret + ret;

}



static const struct bpf_func_proto bpf_sysctl_get_name_proto = {

	.func		= bpf_sysctl_get_name,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_CTX,

	.arg2_type	= ARG_PTR_TO_MEM,

	.arg3_type	= ARG_CONST_SIZE,

	.arg4_type	= ARG_ANYTHING,

};



static const struct bpf_func_proto *

sysctl_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)

{

	switch (func_id) {

	case BPF_FUNC_sysctl_get_name:

		return &bpf_sysctl_get_name_proto;

	default:

		return cgroup_base_func_proto(func_id, prog);

	}

}



static bool sysctl_is_valid_access(int off, int size, enum bpf_access_type type,

				   const struct bpf_prog *prog,