arch/x86/kernel/head64.c

   1 /*
   2  *  prepare to run common code
   3  *
   4  *  Copyright (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
   5  */
   6
   7 #include <linux/init.h>
   8 #include <linux/linkage.h>
   9 #include <linux/types.h>
  10 #include <linux/kernel.h>
  11 #include <linux/string.h>
  12 #include <linux/percpu.h>
  13 #include <linux/start_kernel.h>
  14
  15 #include <asm/processor.h>
  16 #include <asm/proto.h>
  17 #include <asm/smp.h>
  18 #include <asm/setup.h>
  19 #include <asm/desc.h>
  20 #include <asm/pgtable.h>
  21 #include <asm/tlbflush.h>
  22 #include <asm/sections.h>
  23 #include <asm/kdebug.h>
  24 #include <asm/e820.h>
  25
  26 static void __init zap_identity_mappings(void)
  27 {
  28         pgd_t *pgd = pgd_offset_k(0UL);
  29         pgd_clear(pgd);
  30         __flush_tlb_all();
  31 }
  32
  33 /* Don't add a printk in there. printk relies on the PDA which is not initialized
  34    yet. */
  35 static void __init clear_bss(void)
  36 {
  37         memset(__bss_start, 0,
  38                (unsigned long) __bss_stop - (unsigned long) __bss_start);
  39 }
  40
  41 static void __init copy_bootdata(char *real_mode_data)
  42 {
  43         char * command_line;
  44
  45         memcpy(&boot_params, real_mode_data, sizeof boot_params);
  46         if (boot_params.hdr.cmd_line_ptr) {
  47                 command_line = __va(boot_params.hdr.cmd_line_ptr);
  48                 memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);
  49         }
  50 }
  51
  52 #define BIOS_EBDA_SEGMENT 0x40E
  53 #define BIOS_LOWMEM_KILOBYTES 0x413
  54
  55 /*
  56  * The BIOS places the EBDA/XBDA at the top of conventional
  57  * memory, and usually decreases the reported amount of
  58  * conventional memory (int 0x12) too. This also contains a
  59  * workaround for Dell systems that neglect to reserve EBDA.
  60  * The same workaround also avoids a problem with the AMD768MPX
  61  * chipset: reserve a page before VGA to prevent PCI prefetch
  62  * into it (errata #56). Usually the page is reserved anyways,
  63  * unless you have no PS/2 mouse plugged in.
  64  */
  65 static void __init reserve_ebda_region(void)
  66 {
  67         unsigned int lowmem, ebda_addr;
  68
  69         /* To determine the position of the EBDA and the */
  70         /* end of conventional memory, we need to look at */
  71         /* the BIOS data area. In a paravirtual environment */
  72         /* that area is absent. We'll just have to assume */
  73         /* that the paravirt case can handle memory setup */
  74         /* correctly, without our help. */
  75         if (paravirt_enabled())
  76                 return;
  77
  78         /* end of low (conventional) memory */
  79         lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
  80         lowmem <<= 10;
  81
  82         /* start of EBDA area */
  83         ebda_addr = *(unsigned short *)__va(BIOS_EBDA_SEGMENT);
  84         ebda_addr <<= 4;
  85
  86         /* Fixup: bios puts an EBDA in the top 64K segment */
  87         /* of conventional memory, but does not adjust lowmem. */
  88         if ((lowmem - ebda_addr) <= 0x10000)
  89                 lowmem = ebda_addr;
  90
  91         /* Fixup: bios does not report an EBDA at all. */
  92         /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */
  93         if ((ebda_addr == 0) && (lowmem >= 0x9f000))
  94                 lowmem = 0x9f000;
  95
  96         /* Paranoia: should never happen, but... */
  97         if ((lowmem == 0) || (lowmem >= 0x100000))
  98                 lowmem = 0x9f000;
  99
 100         /* reserve all memory between lowmem and the 1MB mark */
 101         reserve_early(lowmem, 0x100000, "BIOS reserved");
 102 }
 103
 104 void __init x86_64_start_kernel(char * real_mode_data)
 105 {
 106         int i;
 107
 108         /*
 109          * Build-time sanity checks on the kernel image and module
 110          * area mappings. (these are purely build-time and produce no code)
 111          */
 112         BUILD_BUG_ON(MODULES_VADDR < KERNEL_IMAGE_START);
 113         BUILD_BUG_ON(MODULES_VADDR-KERNEL_IMAGE_START < KERNEL_IMAGE_SIZE);
 114         BUILD_BUG_ON(MODULES_LEN + KERNEL_IMAGE_SIZE > 2*PUD_SIZE);
 115         BUILD_BUG_ON((KERNEL_IMAGE_START & ~PMD_MASK) != 0);
 116         BUILD_BUG_ON((MODULES_VADDR & ~PMD_MASK) != 0);
 117         BUILD_BUG_ON(!(MODULES_VADDR > __START_KERNEL));
 118         BUILD_BUG_ON(!(((MODULES_END - 1) & PGDIR_MASK) ==
 119                                 (__START_KERNEL & PGDIR_MASK)));
 120
 121         /* clear bss before set_intr_gate with early_idt_handler */
 122         clear_bss();
 123
 124         /* Make NULL pointers segfault */
 125         zap_identity_mappings();
 126
 127         /* Cleanup the over mapped high alias */
 128         cleanup_highmap();
 129
 130         for (i = 0; i < NUM_EXCEPTION_VECTORS; i++) {
 131 #ifdef CONFIG_EARLY_PRINTK
 132                 set_intr_gate(i, &early_idt_handlers[i]);
 133 #else
 134                 set_intr_gate(i, early_idt_handler);
 135 #endif
 136         }
 137         load_idt((const struct desc_ptr *)&idt_descr);
 138
 139         early_printk("Kernel alive\n");
 140
 141         for (i = 0; i < NR_CPUS; i++)
 142                 cpu_pda(i) = &boot_cpu_pda[i];
 143
 144         pda_init(0);
 145         copy_bootdata(__va(real_mode_data));
 146
 147         reserve_early(__pa_symbol(&_text), __pa_symbol(&_end), "TEXT DATA BSS");
 148
 149         /* Reserve INITRD */
 150         if (boot_params.hdr.type_of_loader && boot_params.hdr.ramdisk_image) {
 151                 unsigned long ramdisk_image = boot_params.hdr.ramdisk_image;
 152                 unsigned long ramdisk_size  = boot_params.hdr.ramdisk_size;
 153                 unsigned long ramdisk_end   = ramdisk_image + ramdisk_size;
 154                 reserve_early(ramdisk_image, ramdisk_end, "RAMDISK");
 155         }
 156
 157         reserve_ebda_region();
 158
 159         /*
 160          * At this point everything still needed from the boot loader
 161          * or BIOS or kernel text should be early reserved or marked not
 162          * RAM in e820. All other memory is free game.
 163          */
 164
 165         start_kernel();
 166 }