1 /* -*- linux-c -*- ------------------------------------------------------- *
3 * Copyright (C) 1991, 1992 Linus Torvalds
4 * Copyright 2007 rPath, Inc. - All Rights Reserved
5 * Copyright 2009 Intel Corporation; author H. Peter Anvin
7 * This file is part of the Linux kernel, and is made available under
8 * the terms of the GNU General Public License version 2.
10 * ----------------------------------------------------------------------- */
13 * Memory detection code
18 #define SMAP 0x534d4150 /* ASCII "SMAP" */
20 struct e820_ext_entry {
23 } __attribute__((packed));
25 static int detect_memory_e820(void)
31 struct e820entry *desc = boot_params.e820_map;
32 static struct e820_ext_entry buf; /* static so it is zeroed */
37 /* Important: %edx and %esi are clobbered by some BIOSes,
38 so they must be either used for the error output
39 or explicitly marked clobbered. Given that, assume there
40 is something out there clobbering %ebp and %edi, too. */
41 asm("pushl %%ebp; int $0x15; popl %%ebp; setc %0"
42 : "=d" (err), "+b" (next), "=a" (id), "+c" (size),
43 "=D" (edi), "+m" (buf)
44 : "D" (&buf), "d" (SMAP), "a" (0xe820)
47 /* BIOSes which terminate the chain with CF = 1 as opposed
48 to %ebx = 0 don't always report the SMAP signature on
49 the final, failing, probe. */
53 /* Some BIOSes stop returning SMAP in the middle of
54 the search loop. We don't know exactly how the BIOS
55 screwed up the map at that point, we might have a
56 partial map, the full map, or complete garbage, so
57 just return failure. */
63 /* ACPI 3.0 added the extended flags support. If bit 0
64 in the extended flags is zero, we're supposed to simply
65 ignore the entry -- a backwards incompatible change! */
66 if (size > 20 && !(buf.ext_flags & 1))
71 } while (next && count < ARRAY_SIZE(boot_params.e820_map));
73 return boot_params.e820_entries = count;
76 static int detect_memory_e801(void)
83 asm("stc; int $0x15; setc %0"
84 : "=m" (err), "+a" (ax), "+b" (bx), "+c" (cx), "+d" (dx));
89 /* Do we really need to do this? */
96 return -1; /* Bogus! */
98 /* This ignores memory above 16MB if we have a memory hole
99 there. If someone actually finds a machine with a memory
100 hole at 16MB and no support for 0E820h they should probably
101 generate a fake e820 map. */
102 boot_params.alt_mem_k = (ax == 15*1024) ? (dx << 6)+ax : ax;
107 static int detect_memory_88(void)
113 asm("stc; int $0x15; setc %0" : "=bcdm" (err), "+a" (ax));
115 boot_params.screen_info.ext_mem_k = ax;
120 int detect_memory(void)
124 if (detect_memory_e820() > 0)
127 if (!detect_memory_e801())
130 if (!detect_memory_88())