root/arch/arm/kernel/atags_proc.c

DEFINITIONS

1. atags_read
2. save_atags
3. init_atags_procfs

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/slab.h>
   3 #include <linux/proc_fs.h>
   4 #include <asm/setup.h>
   5 #include <asm/types.h>
   6 #include <asm/page.h>
   7 
   8 struct buffer {
   9         size_t size;
  10         char data[];
  11 };
  12 
  13 static ssize_t atags_read(struct file *file, char __user *buf,
  14                           size_t count, loff_t *ppos)
  15 {
  16         struct buffer *b = PDE_DATA(file_inode(file));
  17         return simple_read_from_buffer(buf, count, ppos, b->data, b->size);
  18 }
  19 
  20 static const struct file_operations atags_fops = {
  21         .read = atags_read,
  22         .llseek = default_llseek,
  23 };
  24 
  25 #define BOOT_PARAMS_SIZE 1536
  26 static char __initdata atags_copy[BOOT_PARAMS_SIZE];
  27 
  28 void __init save_atags(const struct tag *tags)
  29 {
  30         memcpy(atags_copy, tags, sizeof(atags_copy));
  31 }
  32 
  33 static int __init init_atags_procfs(void)
  34 {
  35         /*
  36          * This cannot go into save_atags() because kmalloc and proc don't work
  37          * yet when it is called.
  38          */
  39         struct proc_dir_entry *tags_entry;
  40         struct tag *tag = (struct tag *)atags_copy;
  41         struct buffer *b;
  42         size_t size;
  43 
  44         if (tag->hdr.tag != ATAG_CORE) {
  45                 pr_info("No ATAGs?");
  46                 return -EINVAL;
  47         }
  48 
  49         for (; tag->hdr.size; tag = tag_next(tag))
  50                 ;
  51 
  52         /* include the terminating ATAG_NONE */
  53         size = (char *)tag - atags_copy + sizeof(struct tag_header);
  54 
  55         WARN_ON(tag->hdr.tag != ATAG_NONE);
  56 
  57         b = kmalloc(sizeof(*b) + size, GFP_KERNEL);
  58         if (!b)
  59                 goto nomem;
  60 
  61         b->size = size;
  62         memcpy(b->data, atags_copy, size);
  63 
  64         tags_entry = proc_create_data("atags", 0400, NULL, &atags_fops, b);
  65         if (!tags_entry)
  66                 goto nomem;
  67 
  68         return 0;
  69 
  70 nomem:
  71         kfree(b);
  72         pr_err("Exporting ATAGs: not enough memory\n");
  73 
  74         return -ENOMEM;
  75 }
  76 arch_initcall(init_atags_procfs);