btf: expose BTF info through sysfs

[mirror_ubuntu-jammy-kernel.git] / kernel / bpf / sysfs_btf.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Provide kernel BTF information for introspection and use by eBPF tools.
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kobject.h>
#include <linux/init.h>
#include <linux/sysfs.h>

/* See scripts/link-vmlinux.sh, gen_btf() func for details */
extern char __weak _binary__btf_kernel_bin_start[];
extern char __weak _binary__btf_kernel_bin_end[];

static ssize_t
btf_kernel_read(struct file *file, struct kobject *kobj,
		struct bin_attribute *bin_attr,
		char *buf, loff_t off, size_t len)
{
	memcpy(buf, _binary__btf_kernel_bin_start + off, len);
	return len;
}

static struct bin_attribute bin_attr_btf_kernel __ro_after_init = {
	.attr = { .name = "kernel", .mode = 0444, },
	.read = btf_kernel_read,
};

static struct kobject *btf_kobj;

static int __init btf_kernel_init(void)
{
	int err;

	if (!_binary__btf_kernel_bin_start)
		return 0;

	btf_kobj = kobject_create_and_add("btf", kernel_kobj);
	if (IS_ERR(btf_kobj)) {
		err = PTR_ERR(btf_kobj);
		btf_kobj = NULL;
		return err;
	}

	bin_attr_btf_kernel.size = _binary__btf_kernel_bin_end -
				   _binary__btf_kernel_bin_start;

	return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_kernel);
}

subsys_initcall(btf_kernel_init);