sysfs_btf.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Provide kernel BTF information for introspection and use by eBPF tools.
 4 */
 5#include <linux/kernel.h>
 6#include <linux/module.h>
 7#include <linux/kobject.h>
 8#include <linux/init.h>
 9#include <linux/sysfs.h>
10#include <linux/mm.h>
11#include <linux/io.h>
12#include <linux/btf.h>
13
14/* See scripts/link-vmlinux.sh, gen_btf() func for details */
15extern char __start_BTF[];
16extern char __stop_BTF[];
17
18static int btf_sysfs_vmlinux_mmap(struct file *filp, struct kobject *kobj,
19				  const struct bin_attribute *attr,
20				  struct vm_area_struct *vma)
21{
22	unsigned long pages = PAGE_ALIGN(attr->size) >> PAGE_SHIFT;
23	size_t vm_size = vma->vm_end - vma->vm_start;
24	phys_addr_t addr = __pa_symbol(__start_BTF);
25	unsigned long pfn = addr >> PAGE_SHIFT;
26
27	if (attr->private != __start_BTF || !PAGE_ALIGNED(addr))
28		return -EINVAL;
29
30	if (vma->vm_pgoff)
31		return -EINVAL;
32
33	if (vma->vm_flags & (VM_WRITE | VM_EXEC | VM_MAYSHARE))
34		return -EACCES;
35
36	if (pfn + pages < pfn)
37		return -EINVAL;
38
39	if ((vm_size >> PAGE_SHIFT) > pages)
40		return -EINVAL;
41
42	vm_flags_mod(vma, VM_DONTDUMP, VM_MAYEXEC | VM_MAYWRITE);
43	return remap_pfn_range(vma, vma->vm_start, pfn, vm_size, vma->vm_page_prot);
44}
45
46static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
47	.attr = { .name = "vmlinux", .mode = 0444, },
48	.read = sysfs_bin_attr_simple_read,
49	.mmap = btf_sysfs_vmlinux_mmap,
50};
51
52struct kobject *btf_kobj;
53
54static int __init btf_vmlinux_init(void)
55{
56	bin_attr_btf_vmlinux.private = __start_BTF;
57	bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF;
58
59	if (bin_attr_btf_vmlinux.size == 0)
60		return 0;
61
62	btf_kobj = kobject_create_and_add("btf", kernel_kobj);
63	if (!btf_kobj)
64		return -ENOMEM;
65
66	return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux);
67}
68
69subsys_initcall(btf_vmlinux_init);