78958fca7e
This patch gives an ID to each loaded BTF. The ID is allocated by
the idr like the existing prog-id and map-id.
The bpf_put(map->btf) is moved to __bpf_map_put() so that the
userspace can stop seeing the BTF ID ASAP when the last BTF
refcnt is gone.
It also makes BTF accessible from userspace through the
1. new BPF_BTF_GET_FD_BY_ID command. It is limited to CAP_SYS_ADMIN
which is inline with the BPF_BTF_LOAD cmd and the existing
BPF_[MAP|PROG]_GET_FD_BY_ID cmd.
2. new btf_id (and btf_key_id + btf_value_id) in "struct bpf_map_info"
Once the BTF ID handler is accessible from userspace, freeing a BTF
object has to go through a rcu period. The BPF_BTF_GET_FD_BY_ID cmd
can then be done under a rcu_read_lock() instead of taking
spin_lock.
[Note: A similar rcu usage can be done to the existing
bpf_prog_get_fd_by_id() in a follow up patch]
When processing the BPF_BTF_GET_FD_BY_ID cmd,
refcount_inc_not_zero() is needed because the BTF object
could be already in the rcu dead row . btf_get() is
removed since its usage is currently limited to btf.c
alone. refcount_inc() is used directly instead.
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Alexei Starovoitov <ast@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
50 lines
1.6 KiB
C
50 lines
1.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* Copyright (c) 2018 Facebook */
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#ifndef _LINUX_BTF_H
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#define _LINUX_BTF_H 1
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#include <linux/types.h>
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struct btf;
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struct btf_type;
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union bpf_attr;
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extern const struct file_operations btf_fops;
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void btf_put(struct btf *btf);
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int btf_new_fd(const union bpf_attr *attr);
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struct btf *btf_get_by_fd(int fd);
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int btf_get_info_by_fd(const struct btf *btf,
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const union bpf_attr *attr,
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union bpf_attr __user *uattr);
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/* Figure out the size of a type_id. If type_id is a modifier
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* (e.g. const), it will be resolved to find out the type with size.
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*
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* For example:
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* In describing "const void *", type_id is "const" and "const"
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* refers to "void *". The return type will be "void *".
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*
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* If type_id is a simple "int", then return type will be "int".
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*
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* @btf: struct btf object
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* @type_id: Find out the size of type_id. The type_id of the return
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* type is set to *type_id.
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* @ret_size: It can be NULL. If not NULL, the size of the return
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* type is set to *ret_size.
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* Return: The btf_type (resolved to another type with size info if needed).
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* NULL is returned if type_id itself does not have size info
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* (e.g. void) or it cannot be resolved to another type that
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* has size info.
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* *type_id and *ret_size will not be changed in the
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* NULL return case.
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*/
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const struct btf_type *btf_type_id_size(const struct btf *btf,
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u32 *type_id,
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u32 *ret_size);
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void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
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struct seq_file *m);
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int btf_get_fd_by_id(u32 id);
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u32 btf_id(const struct btf *btf);
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#endif
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