qemu/roms/ipxe/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., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  */
  19
  20 /**
  21  * @file SYSLINUX COM32 helpers
  22  *
  23  */
  24
  25 FILE_LICENCE ( GPL2_OR_LATER );
  26
  27 #include <stdint.h>
  28 #include <realmode.h>
  29 #include <comboot.h>
  30 #include <assert.h>
  31 #include <ipxe/uaccess.h>
  32
  33 static com32sys_t __bss16 ( com32_regs );
  34 #define com32_regs __use_data16 ( com32_regs )
  35
  36 static uint8_t __bss16 ( com32_int_vector );
  37 #define com32_int_vector __use_data16 ( com32_int_vector )
  38
  39 static uint32_t __bss16 ( com32_farcall_proc );
  40 #define com32_farcall_proc __use_data16 ( com32_farcall_proc )
  41
  42 uint16_t __bss16 ( com32_saved_sp );
  43
  44 /**
  45  * Interrupt call helper
  46  */
  47 void __asmcall com32_intcall ( uint8_t interrupt, physaddr_t inregs_phys, physaddr_t outregs_phys ) {
  48
  49         memcpy_user ( virt_to_user( &com32_regs ), 0,
  50                       phys_to_user ( inregs_phys ), 0,
  51                       sizeof(com32sys_t) );
  52
  53         com32_int_vector = interrupt;
  54
  55         __asm__ __volatile__ (
  56                 REAL_CODE ( /* Save all registers */
  57                             "pushal\n\t"
  58                             "pushw %%ds\n\t"
  59                             "pushw %%es\n\t"
  60                             "pushw %%fs\n\t"
  61                             "pushw %%gs\n\t"
  62                             /* Mask off unsafe flags */
  63                             "movl (com32_regs + 40), %%eax\n\t"
  64                             "andl $0x200cd7, %%eax\n\t"
  65                             "movl %%eax, (com32_regs + 40)\n\t"
  66                             /* Load com32_regs into the actual registers */
  67                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
  68                             "movw $com32_regs, %%sp\n\t"
  69                             "popw %%gs\n\t"
  70                             "popw %%fs\n\t"
  71                             "popw %%es\n\t"
  72                             "popw %%ds\n\t"
  73                             "popal\n\t"
  74                             "popfl\n\t"
  75                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
  76                             /* patch INT instruction */
  77                             "pushw %%ax\n\t"
  78                             "movb %%ss:(com32_int_vector), %%al\n\t"
  79                             "movb %%al, %%cs:(com32_intcall_instr + 1)\n\t"
  80                             /* perform a jump to avoid problems with cache
  81                              * consistency in self-modifying code on some CPUs (486)
  82                              */
  83                             "jmp 1f\n"
  84                             "1:\n\t"
  85                             "popw %%ax\n\t"
  86                             "com32_intcall_instr:\n\t"
  87                             /* INT instruction to be patched */
  88                             "int $0xFF\n\t"
  89                             /* Copy regs back to com32_regs */
  90                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
  91                             "movw $(com32_regs + 44), %%sp\n\t"
  92                             "pushfl\n\t"
  93                             "pushal\n\t"
  94                             "pushw %%ds\n\t"
  95                             "pushw %%es\n\t"
  96                             "pushw %%fs\n\t"
  97                             "pushw %%gs\n\t"
  98                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
  99                             /* Restore registers */
 100                             "popw %%gs\n\t"
 101                             "popw %%fs\n\t"
 102                             "popw %%es\n\t"
 103                             "popw %%ds\n\t"
 104                             "popal\n\t")
 105                             : : );
 106
 107         if ( outregs_phys ) {
 108                 memcpy_user ( phys_to_user ( outregs_phys ), 0,
 109                               virt_to_user( &com32_regs ), 0,
 110                               sizeof(com32sys_t) );
 111         }
 112 }
 113
 114 /**
 115  * Farcall helper
 116  */
 117 void __asmcall com32_farcall ( uint32_t proc, physaddr_t inregs_phys, physaddr_t outregs_phys ) {
 118
 119         memcpy_user ( virt_to_user( &com32_regs ), 0,
 120                       phys_to_user ( inregs_phys ), 0,
 121                       sizeof(com32sys_t) );
 122
 123         com32_farcall_proc = proc;
 124
 125         __asm__ __volatile__ (
 126                 REAL_CODE ( /* Save all registers */
 127                             "pushal\n\t"
 128                             "pushw %%ds\n\t"
 129                             "pushw %%es\n\t"
 130                             "pushw %%fs\n\t"
 131                             "pushw %%gs\n\t"
 132                             /* Mask off unsafe flags */
 133                             "movl (com32_regs + 40), %%eax\n\t"
 134                             "andl $0x200cd7, %%eax\n\t"
 135                             "movl %%eax, (com32_regs + 40)\n\t"
 136                             /* Load com32_regs into the actual registers */
 137                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
 138                             "movw $com32_regs, %%sp\n\t"
 139                             "popw %%gs\n\t"
 140                             "popw %%fs\n\t"
 141                             "popw %%es\n\t"
 142                             "popw %%ds\n\t"
 143                             "popal\n\t"
 144                             "popfl\n\t"
 145                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
 146                             /* Call procedure */
 147                             "lcall *%%ss:(com32_farcall_proc)\n\t"
 148                             /* Copy regs back to com32_regs */
 149                             "movw %%sp, %%ss:(com32_saved_sp)\n\t"
 150                             "movw $(com32_regs + 44), %%sp\n\t"
 151                             "pushfl\n\t"
 152                             "pushal\n\t"
 153                             "pushw %%ds\n\t"
 154                             "pushw %%es\n\t"
 155                             "pushw %%fs\n\t"
 156                             "pushw %%gs\n\t"
 157                             "movw %%ss:(com32_saved_sp), %%sp\n\t"
 158                             /* Restore registers */
 159                             "popw %%gs\n\t"
 160                             "popw %%fs\n\t"
 161                             "popw %%es\n\t"
 162                             "popw %%ds\n\t"
 163                             "popal\n\t")
 164                             : : );
 165
 166         if ( outregs_phys ) {
 167                 memcpy_user ( phys_to_user ( outregs_phys ), 0,
 168                               virt_to_user( &com32_regs ), 0,
 169                               sizeof(com32sys_t) );
 170         }
 171 }
 172
 173 /**
 174  * CDECL farcall helper
 175  */
 176 int __asmcall com32_cfarcall ( uint32_t proc, physaddr_t stack, size_t stacksz ) {
 177         int32_t eax;
 178
 179         copy_user_to_rm_stack ( phys_to_user ( stack ), stacksz );
 180         com32_farcall_proc = proc;
 181
 182         __asm__ __volatile__ (
 183                 REAL_CODE ( "lcall *%%ss:(com32_farcall_proc)\n\t" )
 184                 : "=a" (eax)
 185                 :
 186                 : "ecx", "edx" );
 187
 188         remove_user_from_rm_stack ( 0, stacksz );
 189
 190         return eax;
 191 }