path: root/fs/proc/vmcore.c

/*
 *	fs/proc/vmcore.c Interface for accessing the crash
 * 				 dump from the system's previous life.
 * 	Heavily borrowed from fs/proc/kcore.c
 *	Created by: Hariprasad Nellitheertha (hari@in.ibm.com)
 *	Copyright (C) IBM Corporation, 2004. All rights reserved
 *
 */

#include <linux/mm.h>
#include <linux/kcore.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/elfcore.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/printk.h>
#include <linux/bootmem.h>
#include <linux/init.h>
#include <linux/crash_dump.h>
#include <linux/list.h>
#include <linux/vmalloc.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include "internal.h"

/* List representing chunks of contiguous memory areas and their offsets in
 * vmcore file.
 */
static LIST_HEAD(vmcore_list);

/* Stores the pointer to the buffer containing kernel elf core headers. */
static char *elfcorebuf;
static size_t elfcorebuf_sz;
static size_t elfcorebuf_sz_orig;

static char *elfnotes_buf;
static size_t elfnotes_sz;

/* Total size of vmcore file. */
static u64 vmcore_size;

static struct proc_dir_entry *proc_vmcore = NULL;

/*
 * Returns > 0 for RAM pages, 0 for non-RAM pages, < 0 on error
 * The called function has to take care of module refcounting.
 */
static int (*oldmem_pfn_is_ram)(unsigned long pfn);

int register_oldmem_pfn_is_ram(int (*fn)(unsigned long pfn))
{
	if (oldmem_pfn_is_ram)
		return -EBUSY;
	oldmem_pfn_is_ram = fn;
	return 0;
}
EXPORT_SYMBOL_GPL(register_oldmem_pfn_is_ram);

void unregister_oldmem_pfn_is_ram(void)
{
	oldmem_pfn_is_ram = NULL;
	wmb();
}
EXPORT_SYMBOL_GPL(unregister_oldmem_pfn_is_ram);

static int pfn_is_ram(unsigned long pfn)
{
	int (*fn)(unsigned long pfn);
	/* pfn is ram unless fn() checks pagetype */
	int ret = 1;

	/*
	 * Ask hypervisor if the pfn is really ram.
	 * A ballooned page contains no data and reading from such a page
	 * will cause high load in the hypervisor.
	 */
	fn = oldmem_pfn_is_ram;
	if (fn)
		ret = fn(pfn);

	return ret;
}

/* Reads a page from the oldmem device from given offset. */
static ssize_t read_from_oldmem(char *buf, size_t count,
				u64 *ppos, int userbuf)
{
	unsigned long pfn, offset;
	size_t nr_bytes;
	ssize_t read = 0, tmp;

	if (!count)
		return 0;

	offset = (unsigned long)(*ppos % PAGE_SIZE);
	pfn = (unsigned long)(*ppos / PAGE_SIZE);

	do {
		if (count > (PAGE_SIZE - offset))
			nr_bytes = PAGE_SIZE - offset;
		else
			nr_bytes = count;

		/* If pfn is not ram, return zeros for sparse dump files */
		if (pfn_is_ram(pfn) == 0)
			memset(buf, 0, nr_bytes);
		else {
			tmp = copy_oldmem_page(pfn, buf, nr_bytes,
						offset, userbuf);
			if (tmp < 0)
				return tmp;
		}
		*ppos += nr_bytes;
		count -= nr_bytes;
		buf += nr_bytes;
		read += nr_bytes;
		++pfn;
		offset = 0;
	} while (count);

	return read;
}

/* Read from the ELF header and then the crash dump. On error, negative value is
 * returned otherwise number of bytes read are returned.
 */
static ssize_t read_vmcore(struct file *file, char __user *buffer,
				size_t buflen, loff_t *fpos)
{
	ssize_t acc = 0, tmp;
	size_t tsz;
	u64 start;
	struct vmcore *m = NULL;

	if (buflen == 0 || *fpos >= vmcore_size)
		return 0;

	/* trim buflen to not go beyond EOF */
	if (buflen > vmcore_size - *fpos)
		buflen = vmcore_size - *fpos;

	/* Read ELF core header */
	if (*fpos < elfcorebuf_sz) {
		tsz = min(elfcorebuf_sz - (size_t)*fpos, buflen);
		if (copy_to_user(buffer, elfcorebuf + *fpos, tsz))
			return -EFAULT;
		buflen -= tsz;
		*fpos += tsz;
		buffer += tsz;
		acc += tsz;

		/* leave now if filled buffer already */
		if (buflen == 0)
			return acc;
	}

	/* Read Elf note segment */
	if (*fpos < elfcorebuf_sz + elfnotes_sz) {
		void *kaddr;

		tsz = min(elfcorebuf_sz + elfnotes_sz - (size_t)*fpos, buflen);
		kaddr = elfnotes_buf + *fpos - elfcorebuf_sz;
		if (copy_to_user(buffer, k