wimboot/wimboot-2.7.3/src/memmap.c

   1 /*
   2  * Copyright (C) 2021 Michael Brown <mbrown@fensystems.co.uk>.
   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 (at your option) 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
  22  *
  23  * Memory map
  24  *
  25  */
  26
  27 #include <stddef.h>
  28 #include <stdio.h>
  29 #include <string.h>
  30 #include "wimboot.h"
  31 #include "memmap.h"
  32
  33 /** Buffer for INT 15,e820 calls */
  34 static struct e820_entry e820_buf __attribute__ (( section ( ".bss16" ) ));
  35
  36 /** Continuation value for next INT 15,e820 call */
  37 static uint32_t e820_ebx;
  38
  39 /**
  40  * Get system memory map entry
  41  *
  42  * @v prev              Previous system memory map entry, or NULL at start
  43  * @v next              Next system memory map entry, or NULL at end
  44  */
  45 struct e820_entry * memmap_next ( struct e820_entry *prev ) {
  46         struct bootapp_callback_params params;
  47
  48         /* Reset buffer and continuation value if restarting */
  49         if ( ! prev ) {
  50                 memset ( &e820_buf, 0, sizeof ( e820_buf ) );
  51                 e820_ebx = 0;
  52         } else if ( e820_ebx == 0 ) {
  53                 /* Reach the end */
  54                 return NULL;
  55         }
  56
  57         /* Read system memory map */
  58         memset ( &params, 0, sizeof ( params ) );
  59         do {
  60
  61                 /* Call INT 15,e820 */
  62                 params.vector.interrupt = 0x15;
  63                 params.eax = 0xe820;
  64                 params.ebx = e820_ebx;
  65                 params.ecx = sizeof ( e820_buf );
  66                 params.edx = E820_SMAP;
  67                 params.es = BASE_SEG;
  68                 params.edi = ( ( ( void * ) &e820_buf ) -
  69                                ( ( void * ) BASE_ADDRESS ) );
  70                 call_interrupt ( &params );
  71
  72                 /* Record continuation value */
  73                 e820_ebx = params.ebx;
  74
  75                 /* Check result */
  76                 if ( params.eflags & CF ) {
  77                         DBG ( "INT 15,e820 failed: error %02x\n", params.ah );
  78                         break;
  79                 }
  80                 if ( params.eax != E820_SMAP ) {
  81                         DBG ( "INT 15,e820 invalid SMAP signature %08x\n",
  82                               params.eax );
  83                         break;
  84                 }
  85                 DBG2 ( "INT 15,e820 region [%llx,%llx) type %d\n",
  86                        e820_buf.start, ( e820_buf.start + e820_buf.len ),
  87                        e820_buf.type );
  88
  89                 /* Skip non-RAM regions */
  90                 if ( e820_buf.type != E820_TYPE_RAM )
  91                         continue;
  92                 if ( params.ecx > offsetof ( typeof ( e820_buf ), attrs ) ) {
  93                         if ( ! ( e820_buf.attrs & E820_ATTR_ENABLED ) )
  94                                 continue;
  95                         if ( e820_buf.attrs & E820_ATTR_NONVOLATILE )
  96                                 continue;
  97                 }
  98
  99                 /* Return this region */
 100                 return &e820_buf;
 101
 102         } while ( e820_ebx != 0 );
 103
 104         return NULL;
 105 }