arch/powerpc/kernel/crash_dump.c

/*
 * Routines for doing kexec-based kdump.
 *
 * Copyright (C) 2005, IBM Corp.
 *
 * Created by: Michael Ellerman
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2.  See the file COPYING for more details.
 */

#undef DEBUG

#include <linux/crash_dump.h>
#include <linux/bootmem.h>
#include <asm/kdump.h>
#include <asm/lmb.h>
#include <asm/firmware.h>
#include <asm/uaccess.h>

#ifdef DEBUG
#include <asm/udbg.h>
#define DBG(fmt...) udbg_printf(fmt)
#else
#define DBG(fmt...)
#endif

static void __init create_trampoline(unsigned long addr)
{
	/* The maximum range of a single instruction branch, is the current
	 * instruction's address + (32 MB - 4) bytes. For the trampoline we
	 * need to branch to current address + 32 MB. So we insert a nop at
	 * the trampoline address, then the next instruction (+ 4 bytes)
	 * does a branch to (32 MB - 4). The net effect is that when we
	 * branch to "addr" we jump to ("addr" + 32 MB). Although it requires
	 * two instructions it doesn't require any registers.
	 */
	create_instruction(addr, 0x60000000); /* nop */
	create_branch(addr + 4, addr + PHYSICAL_START, 0);
}

void __init kdump_setup(void)
{
	unsigned long i;

	DBG(" -> kdump_setup()\n");

	for (i = KDUMP_TRAMPOLINE_START; i < KDUMP_TRAMPOLINE_END; i += 8) {
		create_trampoline(i);
	}

	create_trampoline(__pa(system_reset_fwnmi) - PHYSICAL_START);
	create_trampoline(__pa(machine_check_fwnmi) - PHYSICAL_START);

	DBG(" <- kdump_setup()\n");
}

static int __init parse_elfcorehdr(char *p)
{
	if (p)
		elfcorehdr_addr = memparse(p, &p);

	return 0;
}
__setup("elfcorehdr=", parse_elfcorehdr);

static int __init parse_savemaxmem(char *p)
{
	if (p)
		saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1;

	return 0;
}
__setup("savemaxmem=", parse_savemaxmem);

/*
 * copy_oldmem_page - copy one page from "oldmem"
 * @pfn: page frame number to be copied
 * @buf: target memory address for the copy; this can be in kernel address
 *      space or user address space (see @userbuf)
 * @csize: number of bytes to copy
 * @offset: offset in bytes into the page (based on pfn) to begin the copy
 * @userbuf: if set, @buf is in user address space, use copy_to_user(),
 *      otherwise @buf is in kernel address space, use memcpy().
 *
 * Copy a page from "oldmem". For this page, there is no pte mapped
 * in the current kernel. We stitch up a pte, similar to kmap_atomic.
 */
ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
			size_t csize, unsigned long offset, int userbuf)
{
	void  *vaddr;

	if (!csize)
		return 0;

	vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);

	if (userbuf) {
		if (copy_to_user((char __user *)buf, (vaddr + offset), csize)) {
			iounmap(vaddr);
			return -EFAULT;
		}
	} else
		memcpy(buf, (vaddr + offset), csize);

	iounmap(vaddr);
	return csize;
}