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 #include <asm/efi.h>
  32
  33 /*
  34  * To make EFI call EFI runtime service in physical addressing mode we need
  35  * prelog/epilog before/after the invocation to disable interrupt, to
  36  * claim EFI runtime service handler exclusively and to duplicate a memory in
  37  * low memory space say 0 - 3G.
  38  */
  39
  40 static unsigned long efi_rt_eflags;
  41 static pgd_t efi_bak_pg_dir_pointer[2];
  42
  43 void efi_call_phys_prelog(void)
  44 {
  45         unsigned long cr4;
  46         unsigned long temp;
  47         struct desc_ptr gdt_descr;
  48
  49         local_irq_save(efi_rt_eflags);
  50
  51         /*
  52          * If I don't have PAE, I should just duplicate two entries in page
  53          * directory. If I have PAE, I just need to duplicate one entry in
  54          * page directory.
  55          */
  56         cr4 = read_cr4_safe();
  57
  58         if (cr4 & X86_CR4_PAE) {
  59                 efi_bak_pg_dir_pointer[0].pgd =
  60                     swapper_pg_dir[pgd_index(0)].pgd;
  61                 swapper_pg_dir[0].pgd =
  62                     swapper_pg_dir[pgd_index(PAGE_OFFSET)].pgd;
  63         } else {
  64                 efi_bak_pg_dir_pointer[0].pgd =
  65                     swapper_pg_dir[pgd_index(0)].pgd;
  66                 efi_bak_pg_dir_pointer[1].pgd =
  67                     swapper_pg_dir[pgd_index(0x400000)].pgd;
  68                 swapper_pg_dir[pgd_index(0)].pgd =
  69                     swapper_pg_dir[pgd_index(PAGE_OFFSET)].pgd;
  70                 temp = PAGE_OFFSET + 0x400000;
  71                 swapper_pg_dir[pgd_index(0x400000)].pgd =
  72                     swapper_pg_dir[pgd_index(temp)].pgd;
  73         }
  74
  75         /*
  76          * After the lock is released, the original page table is restored.
  77          */
  78         __flush_tlb_all();
  79
  80         gdt_descr.address = __pa(get_cpu_gdt_table(0));
  81         gdt_descr.size = GDT_SIZE - 1;
  82         load_gdt(&gdt_descr);
  83 }
  84
  85 void efi_call_phys_epilog(void)
  86 {
  87         unsigned long cr4;
  88         struct desc_ptr gdt_descr;
  89
  90         gdt_descr.address = (unsigned long)get_cpu_gdt_table(0);
  91         gdt_descr.size = GDT_SIZE - 1;
  92         load_gdt(&gdt_descr);
  93
  94         cr4 = read_cr4_safe();
  95
  96         if (cr4 & X86_CR4_PAE) {
  97                 swapper_pg_dir[pgd_index(0)].pgd =
  98                     efi_bak_pg_dir_pointer[0].pgd;
  99         } else {
 100                 swapper_pg_dir[pgd_index(0)].pgd =
 101                     efi_bak_pg_dir_pointer[0].pgd;
 102                 swapper_pg_dir[pgd_index(0x400000)].pgd =
 103                     efi_bak_pg_dir_pointer[1].pgd;
 104         }
 105
 106         /*
 107          * After the lock is released, the original page table is restored.
 108          */
 109         __flush_tlb_all();
 110
 111         local_irq_restore(efi_rt_eflags);
 112 }