449f2ab946
Probe memory (INT 15h: E820, E801, 88). Signed-off-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
99 lines
1.9 KiB
C
99 lines
1.9 KiB
C
/* -*- linux-c -*- ------------------------------------------------------- *
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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* Copyright 2007 rPath, Inc. - All Rights Reserved
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*
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* This file is part of the Linux kernel, and is made available under
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* the terms of the GNU General Public License version 2.
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*
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* ----------------------------------------------------------------------- */
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/*
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* arch/i386/boot/memory.c
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*
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* Memory detection code
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*/
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#include "boot.h"
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#define SMAP 0x534d4150 /* ASCII "SMAP" */
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static int detect_memory_e820(void)
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{
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u32 next = 0;
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u32 size, id;
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u8 err;
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struct e820entry *desc = boot_params.e820_map;
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do {
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size = sizeof(struct e820entry);
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id = SMAP;
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asm("int $0x15; setc %0"
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: "=am" (err), "+b" (next), "+d" (id), "+c" (size),
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"=m" (*desc)
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: "D" (desc), "a" (0xe820));
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if (err || id != SMAP)
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break;
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boot_params.e820_entries++;
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desc++;
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} while (next && boot_params.e820_entries < E820MAX);
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return boot_params.e820_entries;
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}
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static int detect_memory_e801(void)
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{
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u16 ax, bx, cx, dx;
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u8 err;
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bx = cx = dx = 0;
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ax = 0xe801;
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asm("stc; int $0x15; setc %0"
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: "=m" (err), "+a" (ax), "+b" (bx), "+c" (cx), "+d" (dx));
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if (err)
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return -1;
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/* Do we really need to do this? */
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if (cx || dx) {
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ax = cx;
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bx = dx;
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}
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if (ax > 15*1024)
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return -1; /* Bogus! */
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/* This ignores memory above 16MB if we have a memory hole
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there. If someone actually finds a machine with a memory
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hole at 16MB and no support for 0E820h they should probably
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generate a fake e820 map. */
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boot_params.alt_mem_k = (ax == 15*1024) ? (dx << 6)+ax : ax;
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return 0;
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}
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static int detect_memory_88(void)
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{
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u16 ax;
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u8 err;
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ax = 0x8800;
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asm("stc; int $0x15; setc %0" : "=bcdm" (err), "+a" (ax));
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boot_params.screen_info.ext_mem_k = ax;
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return -err;
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}
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int detect_memory(void)
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{
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if (detect_memory_e820() > 0)
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return 0;
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if (!detect_memory_e801())
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return 0;
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return detect_memory_88();
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}
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