arch/x86/kernel/efi_32.c

   1 /*
   2  * Extensible Firmware Interface
   3  *
   4  * Based on Extensible Firmware Interface Specification version 1.0
   5  *
   6  * Copyright (C) 1999 VA Linux Systems
   7  * Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
   8  * Copyright (C) 1999-2002 Hewlett-Packard Co.
   9  *      David Mosberger-Tang <davidm@hpl.hp.com>
  10  *      Stephane Eranian <eranian@hpl.hp.com>
  11  *
  12  * All EFI Runtime Services are not implemented yet as EFI only
  13  * supports physical mode addressing on SoftSDV. This is to be fixed
  14  * in a future version.  --drummond 1999-07-20
  15  *
  16  * Implemented EFI runtime services and virtual mode calls.  --davidm
  17  *
  18  * Goutham Rao: <goutham.rao@intel.com>
  19  *      Skip non-WB memory and ignore empty memory ranges.
  20  */
  21
  22 #include <linux/kernel.h>
  23 #include <linux/types.h>
  24 #include <linux/ioport.h>
  25 #include <linux/efi.h>
  26
  27 #include <asm/io.h>
  28 #include <asm/page.h>
  29 #include <asm/pgtable.h>
  30 #include <asm/tlbflush.h>
  31
  32 /*
  33  * To make EFI call EFI runtime service in physical addressing mode we need
  34  * prelog/epilog before/after the invocation to disable interrupt, to
  35  * claim EFI runtime service handler exclusively and to duplicate a memory in
  36  * low memory space say 0 - 3G.
  37  */
  38
  39 static unsigned long efi_rt_eflags;
  40 static pgd_t efi_bak_pg_dir_pointer[2];
  41
  42 void efi_call_phys_prelog(void)
  43 {
  44         unsigned long cr4;
  45         unsigned long temp;
  46         struct desc_ptr gdt_descr;
  47
  48         local_irq_save(efi_rt_eflags);
  49
  50         /*
  51          * If I don't have PSE, I should just duplicate two entries in page
  52          * directory. If I have PSE, I just need to duplicate one entry in
  53          * page directory.
  54          */
  55         cr4 = read_cr4();
  56
  57         if (cr4 & X86_CR4_PSE) {
  58                 efi_bak_pg_dir_pointer[0].pgd =
  59                     swapper_pg_dir[pgd_index(0)].pgd;
  60                 swapper_pg_dir[0].pgd =
  61                     swapper_pg_dir[pgd_index(PAGE_OFFSET)].pgd;
  62         } else {
  63                 efi_bak_pg_dir_pointer[0].pgd =
  64                     swapper_pg_dir[pgd_index(0)].pgd;
  65                 efi_bak_pg_dir_pointer[1].pgd =
  66                     swapper_pg_dir[pgd_index(0x400000)].pgd;
  67                 swapper_pg_dir[pgd_index(0)].pgd =
  68                     swapper_pg_dir[pgd_index(PAGE_OFFSET)].pgd;
  69                 temp = PAGE_OFFSET + 0x400000;
  70                 swapper_pg_dir[pgd_index(0x400000)].pgd =
  71                     swapper_pg_dir[pgd_index(temp)].pgd;
  72         }
  73
  74         /*
  75          * After the lock is released, the original page table is restored.
  76          */
  77         __flush_tlb_all();
  78
  79         gdt_descr.address = __pa(get_cpu_gdt_table(0));
  80         gdt_descr.size = GDT_SIZE - 1;
  81         load_gdt(&gdt_descr);
  82 }
  83
  84 void efi_call_phys_epilog(void)
  85 {
  86         unsigned long cr4;
  87         struct desc_ptr gdt_descr;
  88
  89         gdt_descr.address = (unsigned long)get_cpu_gdt_table(0);
  90         gdt_descr.size = GDT_SIZE - 1;
  91         load_gdt(&gdt_descr);
  92
  93         cr4 = read_cr4();
  94
  95         if (cr4 & X86_CR4_PSE) {
  96                 swapper_pg_dir[pgd_index(0)].pgd =
  97                     efi_bak_pg_dir_pointer[0].pgd;
  98         } else {
  99                 swapper_pg_dir[pgd_index(0)].pgd =
 100                     efi_bak_pg_dir_pointer[0].pgd;
 101                 swapper_pg_dir[pgd_index(0x400000)].pgd =
 102                     efi_bak_pg_dir_pointer[1].pgd;
 103         }
 104
 105         /*
 106          * After the lock is released, the original page table is restored.
 107          */
 108         __flush_tlb_all();
 109
 110         local_irq_restore(efi_rt_eflags);
 111 }