arch/x86/boot/memory.c

   1 /* -*- linux-c -*- ------------------------------------------------------- *
   2  *
   3  *   Copyright (C) 1991, 1992 Linus Torvalds
   4  *   Copyright 2007 rPath, Inc. - All Rights Reserved
   5  *
   6  *   This file is part of the Linux kernel, and is made available under
   7  *   the terms of the GNU General Public License version 2.
   8  *
   9  * ----------------------------------------------------------------------- */
  10
  11 /*
  12  * arch/i386/boot/memory.c
  13  *
  14  * Memory detection code
  15  */
  16
  17 #include "boot.h"
  18
  19 #define SMAP    0x534d4150      /* ASCII "SMAP" */
  20
  21 static int detect_memory_e820(void)
  22 {
  23         int count = 0;
  24         u32 next = 0;
  25         u32 size, id;
  26         u8 err;
  27         struct e820entry *desc = boot_params.e820_map;
  28
  29         do {
  30                 size = sizeof(struct e820entry);
  31
  32                 /* Important: %edx is clobbered by some BIOSes,
  33                    so it must be either used for the error output
  34                    or explicitly marked clobbered. */
  35                 asm("int $0x15; setc %0"
  36                     : "=d" (err), "+b" (next), "=a" (id), "+c" (size),
  37                       "=m" (*desc)
  38                     : "D" (desc), "d" (SMAP), "a" (0xe820));
  39
  40 <<<<<<< HEAD:arch/x86/boot/memory.c
  41 =======
  42                 /* BIOSes which terminate the chain with CF = 1 as opposed
  43                    to %ebx = 0 don't always report the SMAP signature on
  44                    the final, failing, probe. */
  45                 if (err)
  46                         break;
  47
  48 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:arch/x86/boot/memory.c
  49                 /* Some BIOSes stop returning SMAP in the middle of
  50                    the search loop.  We don't know exactly how the BIOS
  51                    screwed up the map at that point, we might have a
  52                    partial map, the full map, or complete garbage, so
  53                    just return failure. */
  54                 if (id != SMAP) {
  55                         count = 0;
  56                         break;
  57                 }
  58
  59 <<<<<<< HEAD:arch/x86/boot/memory.c
  60                 if (err)
  61                         break;
  62
  63 =======
  64 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:arch/x86/boot/memory.c
  65                 count++;
  66                 desc++;
  67         } while (next && count < E820MAX);
  68
  69         return boot_params.e820_entries = count;
  70 }
  71
  72 static int detect_memory_e801(void)
  73 {
  74         u16 ax, bx, cx, dx;
  75         u8 err;
  76
  77         bx = cx = dx = 0;
  78         ax = 0xe801;
  79         asm("stc; int $0x15; setc %0"
  80             : "=m" (err), "+a" (ax), "+b" (bx), "+c" (cx), "+d" (dx));
  81
  82         if (err)
  83                 return -1;
  84
  85         /* Do we really need to do this? */
  86         if (cx || dx) {
  87                 ax = cx;
  88                 bx = dx;
  89         }
  90
  91         if (ax > 15*1024)
  92                 return -1;      /* Bogus! */
  93
  94         /* This ignores memory above 16MB if we have a memory hole
  95            there.  If someone actually finds a machine with a memory
  96            hole at 16MB and no support for 0E820h they should probably
  97            generate a fake e820 map. */
  98         boot_params.alt_mem_k = (ax == 15*1024) ? (dx << 6)+ax : ax;
  99
 100         return 0;
 101 }
 102
 103 static int detect_memory_88(void)
 104 {
 105         u16 ax;
 106         u8 err;
 107
 108         ax = 0x8800;
 109         asm("stc; int $0x15; setc %0" : "=bcdm" (err), "+a" (ax));
 110
 111         boot_params.screen_info.ext_mem_k = ax;
 112
 113         return -err;
 114 }
 115
 116 int detect_memory(void)
 117 {
 118         int err = -1;
 119
 120         if (detect_memory_e820() > 0)
 121                 err = 0;
 122
 123         if (!detect_memory_e801())
 124                 err = 0;
 125
 126         if (!detect_memory_88())
 127                 err = 0;
 128
 129         return err;
 130 }