path: root/fs/proc/vmcore.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *	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/memblock.h>
#include <linux/init.h>
#include <linux/crash_dump.h>
#include <linux/list.h>
#include <linux/moduleparam.h>
#include <linux/mutex.h>
#include <linux/vmalloc.h>
#include <linux/pagemap.h>
#include <linux/uio.h>
#include <linux/cc_platform.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;
/* Size of all notes minus the device dump notes */
static size_t elfnotes_orig_sz;

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

static struct proc_dir_entry *proc_vmcore;

#ifdef CONFIG_PROC_VMCORE_DEVICE_DUMP
/* Device Dump list and mutex to synchronize access to list */
static LIST_HEAD(vmcoredd_list);
static DEFINE_MUTEX(vmcoredd_mutex);

static bool vmcoredd_disabled;
core_param(novmcoredd, vmcoredd_disabled, bool, 0);
#endif /* CONFIG_PROC_VMCORE_DEVICE_DUMP */

/* Device Dump Size */
static size_t vmcoredd_orig_sz;

static DEFINE_SPINLOCK(vmcore_cb_lock);
DEFINE_STATIC_SRCU(vmcore_cb_srcu);
/* List of registered vmcore callbacks. */
static LIST_HEAD(vmcore_cb_list);
/* Whether the vmcore has been opened once. */
static bool vmcore_opened;

void register_vmcore_cb(struct vmcore_cb *cb)
{
	INIT_LIST_HEAD(&cb->next);
	spin_lock(&vmcore_cb_lock);
	list_add_tail(&cb->next, &vmcore_cb_list);
	/*
	 * Registering a vmcore callback after the vmcore was opened is
	 * very unusual (e.g., manual driver loading).
	 */
	if (vmcore_opened)
		pr_warn_once("Unexpected vmcore callback registration\n");
	spin_unlock(&vmcore_cb_lock);
}
EXPORT_SYMBOL_GPL(register_vmcore_cb);

void unregister_vmcore_cb(struct vmcore_cb *cb)
{
	spin_lock(&vmcore_cb_lock);
	list_del_rcu(&cb->next);
	/*
	 * Unregistering a vmcore callback after the vmcore was opened is
	 * very unusual (e.g., forced driver removal), but we cannot stop
	 * unregistering.
	 */
	if (vmcore_opened)
		pr_warn_once("Unexpected vmcore callback unregistration\n");
	spin_unlock(&vmcore_cb_lock);

	synchronize_srcu(&vmcore_cb_srcu);
}
EXPORT_SYMBOL_GPL(unregister_vmcore_cb);

static bool pfn_is_ram(unsigned long pfn)
{
	struct vmcore_cb *cb;
	bool ret = true;

	list_for_each_entry_srcu(cb, &vmcore_cb_list, next,
				 srcu_read_lock_held(&vmcore_cb_srcu)) {
		if (unlikely(!cb->pfn_is_ram))
			continue;
		ret = cb->pfn_is_ram(cb, pfn);
		if (!ret)
			break;
	}

	return ret;
}

static int open_vmcore(struct inode *inode, struct file *file)
{
	spin_lock(&vmcore_cb_lock);
	vmcore_opened = true;
	spin_unlock(&vmcore_cb_lock);

	return 0;
}

/* Reads a page from the oldmem device from given offset. */
ssize_t read_from_oldmem(struct iov_iter *iter, size_t count,
			 u64 *ppos, bool encrypted)
{
	unsigned long pfn, offset;
	ssize_t nr_bytes;
	ssize_t read = 0, tmp;
	int idx;

	if (!count)
		return 0;

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

	idx = srcu_read_lock(&vmcore_cb_srcu);
	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)) {
			tmp = iov_iter_zero(nr_bytes, iter);
		} else {
			if (encrypted)
				tmp = copy_oldmem_page_encrypted(iter, pfn,
								 nr_bytes,
								 offset);
			else
				tmp = copy_oldmem_page(iter, pfn, nr_bytes,
						       offset);
		}
		if (tmp < nr_bytes) {
			srcu_read_unlock(&vmcore_cb_srcu, idx);
			return -EFAULT;
		}

		*ppos += nr_bytes;
		count -= nr_bytes;
		read += nr_bytes;
		++pfn;
		offset = 0;
	} while (count);
	srcu_read_unlock(&vmcore_cb_srcu, idx);

	return read;
}

/*
 * Architectures may override this function to allocate ELF header in 2nd kernel
 */
int __weak elfcorehdr_alloc(unsigned long long *addr, unsigned long long *size)
{
	return 0;
}

/*
 * Architectures may override this function to free header
 */
void __weak elfcorehdr_free(unsigned long long addr)
{}

/*
 * Architectures may override this function to read from ELF header
 */
ssize_t __weak elfcorehdr_read(char *buf, size_t count, u64 *ppos)
{
	struct kvec kvec = { .iov_base = buf, .iov_len = count };
	struct iov_iter iter;

	iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, count);

	return read_from_oldmem(&iter, count, ppos, false);
}

/*
 * Architectures may override this function to