src/arch/i386/interface/syslinux/com32_call.c

   1 /*
   2  * Copyright (C) 2008 Daniel Verkamp <daniel@drv.nu>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 /**
  20  * @file SYSLINUX COM32 helpers
  21  *
  22  */
  23
  24 #include <stdint.h>
  25 #include <realmode.h>
  26 #include <comboot.h>
  27 #include <assert.h>
  28 #include <gpxe/uaccess.h>
  29
  30 static com32sys_t __bss16 ( com32_regs );
  31 #define com32_regs __use_data16 ( com32_regs )
  32
  33 static uint8_t __bss16 ( com32_int_vector );
  34 #define com32_int_vector __use_data16 ( com32_int_vector )
  35
  36 static uint32_t __bss16 ( com32_farcall_proc );
  37 #define com32_farcall_proc __use_data16 ( com32_farcall_proc )
  38
  39 uint16_t __bss16 ( com32_saved_sp );
  40
  41 /**
  42  * Interrupt call helper
  43  */
  44 void __cdecl com32_intcall ( uint8_t interrupt, physaddr_t inregs_phys, physaddr_t outregs_phys ) {
  45
  46         memcpy_user ( virt_to_user( &com32_regs ), 0,
  47                       phys_to_user ( inregs_phys ), 0,
  48                       sizeof(com32sys_t) );
  49
  50         com32_int_vector = interrupt;
  51
  52         __asm__ __volatile__ (
  53                 REAL_CODE ( /* Save all registers */
  54                             "pushal\n\t"
  55                             "pushw %%ds\n\t"
  56                             "pushw %%es\n\t"
  57                             "pushw %%fs\n\t"
  58                             "pushw %%gs\n\t"
  59                             /* Mask off unsafe flags */
  60                             "movl (com32_regs + 40), %%eax\n\t"
  61                             "andl $0x200cd7, %%eax\n\t"
  62                             "movl %%eax, (com32_regs + 40)\n\t"
  63                             /* Load com32_regs into the actual registers */
  64                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
  65                             "movw $com32_regs, %%sp\n\t"
  66                             "popw %%gs\n\t"
  67                             "popw %%fs\n\t"
  68                             "popw %%es\n\t"
  69                             "popw %%ds\n\t"
  70                             "popal\n\t"
  71                             "popfl\n\t"
  72                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
  73                             /* patch INT instruction */
  74                             "pushw %%ax\n\t"
  75                             "movb %%ss:(com32_int_vector), %%al\n\t"
  76                             "movb %%al, %%cs:(com32_intcall_instr + 1)\n\t"
  77                             /* perform a jump to avoid problems with cache
  78                              * consistency in self-modifying code on some CPUs (486)
  79                              */
  80                             "jmp 1f\n"
  81                             "1:\n\t"
  82                             "popw %%ax\n\t"
  83                             "com32_intcall_instr:\n\t"
  84                             /* INT instruction to be patched */
  85                             "int $0xFF\n\t"
  86                             /* Copy regs back to com32_regs */
  87                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
  88                             "movw $(com32_regs + 44), %%sp\n\t"
  89                             "pushfl\n\t"
  90                             "pushal\n\t"
  91                             "pushw %%ds\n\t"
  92                             "pushw %%es\n\t"
  93                             "pushw %%fs\n\t"
  94                             "pushw %%gs\n\t"
  95                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
  96                             /* Restore registers */
  97                             "popw %%gs\n\t"
  98                             "popw %%fs\n\t"
  99                             "popw %%es\n\t"
 100                             "popw %%ds\n\t"
 101                             "popal\n\t")
 102                             : : );
 103
 104         if ( outregs_phys ) {
 105                 memcpy_user ( phys_to_user ( outregs_phys ), 0,
 106                               virt_to_user( &com32_regs ), 0,
 107                               sizeof(com32sys_t) );
 108         }
 109 }
 110
 111 /**
 112  * Farcall helper
 113  */
 114 void __cdecl com32_farcall ( uint32_t proc, physaddr_t inregs_phys, physaddr_t outregs_phys ) {
 115
 116         memcpy_user ( virt_to_user( &com32_regs ), 0,
 117                       phys_to_user ( inregs_phys ), 0,
 118                       sizeof(com32sys_t) );
 119
 120         com32_farcall_proc = proc;
 121
 122         __asm__ __volatile__ (
 123                 REAL_CODE ( /* Save all registers */
 124                             "pushal\n\t"
 125                             "pushw %%ds\n\t"
 126                             "pushw %%es\n\t"
 127                             "pushw %%fs\n\t"
 128                             "pushw %%gs\n\t"
 129                             /* Mask off unsafe flags */
 130                             "movl (com32_regs + 40), %%eax\n\t"
 131                             "andl $0x200cd7, %%eax\n\t"
 132                             "movl %%eax, (com32_regs + 40)\n\t"
 133                             /* Load com32_regs into the actual registers */
 134                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
 135                             "movw $com32_regs, %%sp\n\t"
 136                             "popw %%gs\n\t"
 137                             "popw %%fs\n\t"
 138                             "popw %%es\n\t"
 139                             "popw %%ds\n\t"
 140                             "popal\n\t"
 141                             "popfl\n\t"
 142                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
 143                             /* Call procedure */
 144                             "lcall *%%ss:(com32_farcall_proc)\n\t"
 145                             /* Copy regs back to com32_regs */
 146                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
 147                             "movw $(com32_regs + 44), %%sp\n\t"
 148                             "pushfl\n\t"
 149                             "pushal\n\t"
 150                             "pushw %%ds\n\t"
 151                             "pushw %%es\n\t"
 152                             "pushw %%fs\n\t"
 153                             "pushw %%gs\n\t"
 154                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
 155                             /* Restore registers */
 156                             "popw %%gs\n\t"
 157                             "popw %%fs\n\t"
 158                             "popw %%es\n\t"
 159                             "popw %%ds\n\t"
 160                             "popal\n\t")
 161                             : : );
 162
 163         if ( outregs_phys ) {
 164                 memcpy_user ( phys_to_user ( outregs_phys ), 0,
 165                               virt_to_user( &com32_regs ), 0,
 166                               sizeof(com32sys_t) );
 167         }
 168 }
 169
 170 /**
 171  * CDECL farcall helper
 172  */
 173 int __cdecl com32_cfarcall ( uint32_t proc, physaddr_t stack, size_t stacksz ) {
 174         int32_t eax;
 175
 176         copy_user_to_rm_stack ( phys_to_user ( stack ), stacksz );
 177         com32_farcall_proc = proc;
 178
 179         __asm__ __volatile__ (
 180                 REAL_CODE ( "lcall *%%ss:(com32_farcall_proc)\n\t" )
 181                 : "=a" (eax)
 182                 :
 183                 : "ecx", "edx" );
 184
 185         remove_user_from_rm_stack ( 0, stacksz );
 186
 187         return eax;
 188 }