arch/x86_64/kernel/machine_kexec.c

   1 /*
   2  * machine_kexec.c - handle transition of Linux booting another kernel
   3  * Copyright (C) 2002-2005 Eric Biederman  <ebiederm@xmission.com>
   4  *
   5  * This source code is licensed under the GNU General Public License,
   6  * Version 2.  See the file COPYING for more details.
   7  */
   8
   9 #include <linux/mm.h>
  10 #include <linux/kexec.h>
  11 #include <linux/string.h>
  12 #include <linux/reboot.h>
  13 #include <asm/pgtable.h>
  14 #include <asm/tlbflush.h>
  15 #include <asm/mmu_context.h>
  16 #include <asm/io.h>
  17
  18 static void init_level2_page(pmd_t *level2p, unsigned long addr)
  19 {
  20         unsigned long end_addr;
  21
  22         addr &= PAGE_MASK;
  23         end_addr = addr + PUD_SIZE;
  24         while (addr < end_addr) {
  25                 set_pmd(level2p++, __pmd(addr | __PAGE_KERNEL_LARGE_EXEC));
  26                 addr += PMD_SIZE;
  27         }
  28 }
  29
  30 static int init_level3_page(struct kimage *image, pud_t *level3p,
  31                                 unsigned long addr, unsigned long last_addr)
  32 {
  33         unsigned long end_addr;
  34         int result;
  35
  36         result = 0;
  37         addr &= PAGE_MASK;
  38         end_addr = addr + PGDIR_SIZE;
  39         while ((addr < last_addr) && (addr < end_addr)) {
  40                 struct page *page;
  41                 pmd_t *level2p;
  42
  43                 page = kimage_alloc_control_pages(image, 0);
  44                 if (!page) {
  45                         result = -ENOMEM;
  46                         goto out;
  47                 }
  48                 level2p = (pmd_t *)page_address(page);
  49                 init_level2_page(level2p, addr);
  50                 set_pud(level3p++, __pud(__pa(level2p) | _KERNPG_TABLE));
  51                 addr += PUD_SIZE;
  52         }
  53         /* clear the unused entries */
  54         while (addr < end_addr) {
  55                 pud_clear(level3p++);
  56                 addr += PUD_SIZE;
  57         }
  58 out:
  59         return result;
  60 }
  61
  62
  63 static int init_level4_page(struct kimage *image, pgd_t *level4p,
  64                                 unsigned long addr, unsigned long last_addr)
  65 {
  66         unsigned long end_addr;
  67         int result;
  68
  69         result = 0;
  70         addr &= PAGE_MASK;
  71         end_addr = addr + (PTRS_PER_PGD * PGDIR_SIZE);
  72         while ((addr < last_addr) && (addr < end_addr)) {
  73                 struct page *page;
  74                 pud_t *level3p;
  75
  76                 page = kimage_alloc_control_pages(image, 0);
  77                 if (!page) {
  78                         result = -ENOMEM;
  79                         goto out;
  80                 }
  81                 level3p = (pud_t *)page_address(page);
  82                 result = init_level3_page(image, level3p, addr, last_addr);
  83                 if (result) {
  84                         goto out;
  85                 }
  86                 set_pgd(level4p++, __pgd(__pa(level3p) | _KERNPG_TABLE));
  87                 addr += PGDIR_SIZE;
  88         }
  89         /* clear the unused entries */
  90         while (addr < end_addr) {
  91                 pgd_clear(level4p++);
  92                 addr += PGDIR_SIZE;
  93         }
  94 out:
  95         return result;
  96 }
  97
  98
  99 static int init_pgtable(struct kimage *image, unsigned long start_pgtable)
 100 {
 101         pgd_t *level4p;
 102         level4p = (pgd_t *)__va(start_pgtable);
 103         return init_level4_page(image, level4p, 0, end_pfn << PAGE_SHIFT);
 104 }
 105
 106 static void set_idt(void *newidt, u16 limit)
 107 {
 108         struct desc_ptr curidt;
 109
 110         /* x86-64 supports unaliged loads & stores */
 111         curidt.size    = limit;
 112         curidt.address = (unsigned long)newidt;
 113
 114         __asm__ __volatile__ (
 115                 "lidtq %0\n"
 116                 : : "m" (curidt)
 117                 );
 118 };
 119
 120
 121 static void set_gdt(void *newgdt, u16 limit)
 122 {
 123         struct desc_ptr curgdt;
 124
 125         /* x86-64 supports unaligned loads & stores */
 126         curgdt.size    = limit;
 127         curgdt.address = (unsigned long)newgdt;
 128
 129         __asm__ __volatile__ (
 130                 "lgdtq %0\n"
 131                 : : "m" (curgdt)
 132                 );
 133 };
 134
 135 static void load_segments(void)
 136 {
 137         __asm__ __volatile__ (
 138                 "\tmovl %0,%%ds\n"
 139                 "\tmovl %0,%%es\n"
 140                 "\tmovl %0,%%ss\n"
 141                 "\tmovl %0,%%fs\n"
 142                 "\tmovl %0,%%gs\n"
 143                 : : "a" (__KERNEL_DS)
 144                 );
 145 }
 146
 147 typedef NORET_TYPE void (*relocate_new_kernel_t)(unsigned long indirection_page,
 148                                         unsigned long control_code_buffer,
 149                                         unsigned long start_address,
 150                                         unsigned long pgtable) ATTRIB_NORET;
 151
 152 const extern unsigned char relocate_new_kernel[];
 153 const extern unsigned long relocate_new_kernel_size;
 154
 155 int machine_kexec_prepare(struct kimage *image)
 156 {
 157         unsigned long start_pgtable, control_code_buffer;
 158         int result;
 159
 160         /* Calculate the offsets */
 161         start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
 162         control_code_buffer = start_pgtable + PAGE_SIZE;
 163
 164         /* Setup the identity mapped 64bit page table */
 165         result = init_pgtable(image, start_pgtable);
 166         if (result)
 167                 return result;
 168
 169         /* Place the code in the reboot code buffer */
 170         memcpy(__va(control_code_buffer), relocate_new_kernel,
 171                                                 relocate_new_kernel_size);
 172
 173         return 0;
 174 }
 175
 176 void machine_kexec_cleanup(struct kimage *image)
 177 {
 178         return;
 179 }
 180
 181 /*
 182  * Do not allocate memory (or fail in any way) in machine_kexec().
 183  * We are past the point of no return, committed to rebooting now.
 184  */
 185 NORET_TYPE void machine_kexec(struct kimage *image)
 186 {
 187         unsigned long page_list;
 188         unsigned long control_code_buffer;
 189         unsigned long start_pgtable;
 190         relocate_new_kernel_t rnk;
 191
 192         /* Interrupts aren't acceptable while we reboot */
 193         local_irq_disable();
 194
 195         /* Calculate the offsets */
 196         page_list = image->head;
 197         start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
 198         control_code_buffer = start_pgtable + PAGE_SIZE;
 199
 200         /* Set the low half of the page table to my identity mapped
 201          * page table for kexec.  Leave the high half pointing at the
 202          * kernel pages.   Don't bother to flush the global pages
 203          * as that will happen when I fully switch to my identity mapped
 204          * page table anyway.
 205          */
 206         memcpy(__va(read_cr3()), __va(start_pgtable), PAGE_SIZE/2);
 207         __flush_tlb();
 208
 209
 210         /* The segment registers are funny things, they are
 211          * automatically loaded from a table, in memory wherever you
 212          * set them to a specific selector, but this table is never
 213          * accessed again unless you set the segment to a different selector.
 214          *
 215          * The more common model are caches where the behide
 216          * the scenes work is done, but is also dropped at arbitrary
 217          * times.
 218          *
 219          * I take advantage of this here by force loading the
 220          * segments, before I zap the gdt with an invalid value.
 221          */
 222         load_segments();
 223         /* The gdt & idt are now invalid.
 224          * If you want to load them you must set up your own idt & gdt.
 225          */
 226         set_gdt(phys_to_virt(0),0);
 227         set_idt(phys_to_virt(0),0);
 228         /* now call it */
 229         rnk = (relocate_new_kernel_t) control_code_buffer;
 230         (*rnk)(page_list, control_code_buffer, image->start, start_pgtable);
 231 }