// 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>
#include <linux/mm.h>
#include <linux/io.h>
#include <linux/btf.h>

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

static int btf_sysfs_vmlinux_mmap(struct file *filp, struct kobject *kobj,
                                  const struct bin_attribute *attr,
                                  struct vm_area_struct *vma)
{
        unsigned long pages = PAGE_ALIGN(attr->size) >> PAGE_SHIFT;
        size_t vm_size = vma->vm_end - vma->vm_start;
        phys_addr_t addr = __pa_symbol(__start_BTF);
        unsigned long pfn = addr >> PAGE_SHIFT;

        if (attr->private != __start_BTF || !PAGE_ALIGNED(addr))
                return -EINVAL;

        if (vma->vm_pgoff)
                return -EINVAL;

        if (vma->vm_flags & (VM_WRITE | VM_EXEC | VM_MAYSHARE))
                return -EACCES;

        if (pfn + pages < pfn)
                return -EINVAL;

        if ((vm_size >> PAGE_SHIFT) > pages)
                return -EINVAL;

        vm_flags_mod(vma, VM_DONTDUMP, VM_MAYEXEC | VM_MAYWRITE);
        return remap_pfn_range(vma, vma->vm_start, pfn, vm_size, vma->vm_page_prot);
}

static struct bin_attribute bin_attr_btf_vmlinux __ro_after_init = {
        .attr = { .name = "vmlinux", .mode = 0444, },
        .read = sysfs_bin_attr_simple_read,
        .mmap = btf_sysfs_vmlinux_mmap,
};

struct kobject *btf_kobj;

static int __init btf_vmlinux_init(void)
{
        bin_attr_btf_vmlinux.private = __start_BTF;
        bin_attr_btf_vmlinux.size = __stop_BTF - __start_BTF;

        if (bin_attr_btf_vmlinux.size == 0)
                return 0;

        btf_kobj = kobject_create_and_add("btf", kernel_kobj);
        if (!btf_kobj)
                return -ENOMEM;

        return sysfs_create_bin_file(btf_kobj, &bin_attr_btf_vmlinux);
}

subsys_initcall(btf_vmlinux_init);