atags_proc.c

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#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <asm/setup.h>
#include <asm/types.h>
#include <asm/page.h>

struct buffer {
    size_t size;
    char data[];
};

static int
read_buffer(char* page, char** start, off_t off, int count,
    int* eof, void* data)
{
    struct buffer *buffer = (struct buffer *)data;

    if (off >= buffer->size) {
        *eof = 1;
        return 0;
    }

    count = min((int) (buffer->size - off), count);

    memcpy(page, &buffer->data[off], count);

    return count;
}

#define BOOT_PARAMS_SIZE 1536
static char __initdata atags_copy[BOOT_PARAMS_SIZE];

void __init save_atags(const struct tag *tags)
{
    memcpy(atags_copy, tags, sizeof(atags_copy));
}

static int __init init_atags_procfs(void)
{
    /*
     * This cannot go into save_atags() because kmalloc and proc don't work
     * yet when it is called.
     */
    struct proc_dir_entry *tags_entry;
    struct tag *tag = (struct tag *)atags_copy;
    struct buffer *b;
    size_t size;

    if (tag->hdr.tag != ATAG_CORE) {
        printk(KERN_INFO "No ATAGs?");
        return -EINVAL;
    }

    for (; tag->hdr.size; tag = tag_next(tag))
        ;

    /* include the terminating ATAG_NONE */
    size = (char *)tag - atags_copy + sizeof(struct tag_header);

    WARN_ON(tag->hdr.tag != ATAG_NONE);

    b = kmalloc(sizeof(*b) + size, GFP_KERNEL);
    if (!b)
        goto nomem;

    b->size = size;
    memcpy(b->data, atags_copy, size);

    tags_entry = create_proc_read_entry("atags", 0400,
            NULL, read_buffer, b);

    if (!tags_entry)
        goto nomem;

    return 0;

nomem:
    kfree(b);
    printk(KERN_ERR "Exporting ATAGs: not enough memory\n");

    return -ENOMEM;
}
arch_initcall(init_atags_procfs);