arch/powerpc/kernel/crash_dump.c

   1 /*
   2  * Routines for doing kexec-based kdump.
   3  *
   4  * Copyright (C) 2005, IBM Corp.
   5  *
   6  * Created by: Michael Ellerman
   7  *
   8  * This source code is licensed under the GNU General Public License,
   9  * Version 2.  See the file COPYING for more details.
  10  */
  11
  12 #undef DEBUG
  13
  14 #include <linux/crash_dump.h>
  15 #include <linux/bootmem.h>
  16 #include <asm/kdump.h>
  17 #include <asm/lmb.h>
  18 #include <asm/firmware.h>
  19 #include <asm/uaccess.h>
  20
  21 #ifdef DEBUG
  22 #include <asm/udbg.h>
  23 #define DBG(fmt...) udbg_printf(fmt)
  24 #else
  25 #define DBG(fmt...)
  26 #endif
  27
  28 void reserve_kdump_trampoline(void)
  29 {
  30         lmb_reserve(0, KDUMP_RESERVE_LIMIT);
  31 }
  32
  33 static void __init create_trampoline(unsigned long addr)
  34 {
  35         /* The maximum range of a single instruction branch, is the current
  36          * instruction's address + (32 MB - 4) bytes. For the trampoline we
  37          * need to branch to current address + 32 MB. So we insert a nop at
  38          * the trampoline address, then the next instruction (+ 4 bytes)
  39          * does a branch to (32 MB - 4). The net effect is that when we
  40          * branch to "addr" we jump to ("addr" + 32 MB). Although it requires
  41          * two instructions it doesn't require any registers.
  42          */
  43         create_instruction(addr, 0x60000000); /* nop */
  44         create_branch(addr + 4, addr + PHYSICAL_START, 0);
  45 }
  46
  47 void __init setup_kdump_trampoline(void)
  48 {
  49         unsigned long i;
  50
  51         DBG(" -> setup_kdump_trampoline()\n");
  52
  53         for (i = KDUMP_TRAMPOLINE_START; i < KDUMP_TRAMPOLINE_END; i += 8) {
  54                 create_trampoline(i);
  55         }
  56
  57         create_trampoline(__pa(system_reset_fwnmi) - PHYSICAL_START);
  58         create_trampoline(__pa(machine_check_fwnmi) - PHYSICAL_START);
  59
  60         DBG(" <- setup_kdump_trampoline()\n");
  61 }
  62
  63 #ifdef CONFIG_PROC_VMCORE
  64 static int __init parse_elfcorehdr(char *p)
  65 {
  66         if (p)
  67                 elfcorehdr_addr = memparse(p, &p);
  68
  69         return 1;
  70 }
  71 __setup("elfcorehdr=", parse_elfcorehdr);
  72 #endif
  73
  74 static int __init parse_savemaxmem(char *p)
  75 {
  76         if (p)
  77                 saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1;
  78
  79         return 1;
  80 }
  81 __setup("savemaxmem=", parse_savemaxmem);
  82
  83 /**
  84  * copy_oldmem_page - copy one page from "oldmem"
  85  * @pfn: page frame number to be copied
  86  * @buf: target memory address for the copy; this can be in kernel address
  87  *      space or user address space (see @userbuf)
  88  * @csize: number of bytes to copy
  89  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  90  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  91  *      otherwise @buf is in kernel address space, use memcpy().
  92  *
  93  * Copy a page from "oldmem". For this page, there is no pte mapped
  94  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  95  */
  96 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  97                         size_t csize, unsigned long offset, int userbuf)
  98 {
  99         void  *vaddr;
 100
 101         if (!csize)
 102                 return 0;
 103
 104         vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);
 105
 106         if (userbuf) {
 107                 if (copy_to_user((char __user *)buf, (vaddr + offset), csize)) {
 108                         iounmap(vaddr);
 109                         return -EFAULT;
 110                 }
 111         } else
 112                 memcpy(buf, (vaddr + offset), csize);
 113
 114         iounmap(vaddr);
 115         return csize;
 116 }