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 static void __init create_trampoline(unsigned long addr)
  29 {
  30         /* The maximum range of a single instruction branch, is the current
  31          * instruction's address + (32 MB - 4) bytes. For the trampoline we
  32          * need to branch to current address + 32 MB. So we insert a nop at
  33          * the trampoline address, then the next instruction (+ 4 bytes)
  34          * does a branch to (32 MB - 4). The net effect is that when we
  35          * branch to "addr" we jump to ("addr" + 32 MB). Although it requires
  36          * two instructions it doesn't require any registers.
  37          */
  38         create_instruction(addr, 0x60000000); /* nop */
  39         create_branch(addr + 4, addr + PHYSICAL_START, 0);
  40 }
  41
  42 void __init kdump_setup(void)
  43 {
  44         unsigned long i;
  45
  46         DBG(" -> kdump_setup()\n");
  47
  48         for (i = KDUMP_TRAMPOLINE_START; i < KDUMP_TRAMPOLINE_END; i += 8) {
  49                 create_trampoline(i);
  50         }
  51
  52         create_trampoline(__pa(system_reset_fwnmi) - PHYSICAL_START);
  53         create_trampoline(__pa(machine_check_fwnmi) - PHYSICAL_START);
  54
  55         DBG(" <- kdump_setup()\n");
  56 }
  57
  58 #ifdef CONFIG_PROC_VMCORE
  59 static int __init parse_elfcorehdr(char *p)
  60 {
  61         if (p)
  62                 elfcorehdr_addr = memparse(p, &p);
  63
  64         return 0;
  65 }
  66 __setup("elfcorehdr=", parse_elfcorehdr);
  67 #endif
  68
  69 static int __init parse_savemaxmem(char *p)
  70 {
  71         if (p)
  72                 saved_max_pfn = (memparse(p, &p) >> PAGE_SHIFT) - 1;
  73
  74         return 0;
  75 }
  76 __setup("savemaxmem=", parse_savemaxmem);
  77
  78 /*
  79  * copy_oldmem_page - copy one page from "oldmem"
  80  * @pfn: page frame number to be copied
  81  * @buf: target memory address for the copy; this can be in kernel address
  82  *      space or user address space (see @userbuf)
  83  * @csize: number of bytes to copy
  84  * @offset: offset in bytes into the page (based on pfn) to begin the copy
  85  * @userbuf: if set, @buf is in user address space, use copy_to_user(),
  86  *      otherwise @buf is in kernel address space, use memcpy().
  87  *
  88  * Copy a page from "oldmem". For this page, there is no pte mapped
  89  * in the current kernel. We stitch up a pte, similar to kmap_atomic.
  90  */
  91 ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
  92                         size_t csize, unsigned long offset, int userbuf)
  93 {
  94         void  *vaddr;
  95
  96         if (!csize)
  97                 return 0;
  98
  99         vaddr = __ioremap(pfn << PAGE_SHIFT, PAGE_SIZE, 0);
 100
 101         if (userbuf) {
 102                 if (copy_to_user((char __user *)buf, (vaddr + offset), csize)) {
 103                         iounmap(vaddr);
 104                         return -EFAULT;
 105                 }
 106         } else
 107                 memcpy(buf, (vaddr + offset), csize);
 108
 109         iounmap(vaddr);
 110         return csize;
 111 }