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https://github.com/torvalds/linux
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bca23dba76
Remove ACPI 3 E820 extended memory attributes support. At least one
vendor actively set all the flags to zero, but left ECX on return at
24. This bug may be present in other BIOSes.
The breakage functionally means the ACPI 3 flags are probably
completely useless, and that no OS any time soon is going to rely on
their existence. Therefore, drop support completely. We may want to
revisit this question in the future, if we find ourselves actually
needing the flags.
This reverts all or part of the following checkins:
cd670599b7
c549e71d07
However, retain the part from the latter commit that copies e820 into
a temporary buffer; that is an unrelated BIOS workaround. Put in a
comment to explain that part.
See https://bugzilla.redhat.com/show_bug.cgi?id=499396 for some
additional information.
[ Impact: detect all memory on affected machines ]
Reported-by: Thomas J. Baker <tjb@unh.edu>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Acked-by: Len Brown <len.brown@intel.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Cc: Kyle McMartin <kmcmartin@redhat.com>
Cc: Matt Domsch <matt_domsch@dell.com>
138 lines
3.4 KiB
C
138 lines
3.4 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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* Copyright 2009 Intel Corporation; author H. Peter Anvin
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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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* 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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int count = 0;
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u32 next = 0;
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u32 size, id, edi;
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u8 err;
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struct e820entry *desc = boot_params.e820_map;
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static struct e820entry buf; /* static so it is zeroed */
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/*
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* Note: at least one BIOS is known which assumes that the
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* buffer pointed to by one e820 call is the same one as
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* the previous call, and only changes modified fields. Therefore,
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* we use a temporary buffer and copy the results entry by entry.
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*
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* This routine deliberately does not try to account for
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* ACPI 3+ extended attributes. This is because there are
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* BIOSes in the field which report zero for the valid bit for
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* all ranges, and we don't currently make any use of the
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* other attribute bits. Revisit this if we see the extended
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* attribute bits deployed in a meaningful way in the future.
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*/
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do {
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size = sizeof buf;
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/* Important: %edx and %esi are clobbered by some BIOSes,
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so they must be either used for the error output
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or explicitly marked clobbered. Given that, assume there
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is something out there clobbering %ebp and %edi, too. */
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asm("pushl %%ebp; int $0x15; popl %%ebp; setc %0"
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: "=d" (err), "+b" (next), "=a" (id), "+c" (size),
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"=D" (edi), "+m" (buf)
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: "D" (&buf), "d" (SMAP), "a" (0xe820)
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: "esi");
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/* BIOSes which terminate the chain with CF = 1 as opposed
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to %ebx = 0 don't always report the SMAP signature on
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the final, failing, probe. */
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if (err)
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break;
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/* Some BIOSes stop returning SMAP in the middle of
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the search loop. We don't know exactly how the BIOS
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screwed up the map at that point, we might have a
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partial map, the full map, or complete garbage, so
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just return failure. */
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if (id != SMAP) {
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count = 0;
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break;
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}
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*desc++ = buf;
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count++;
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} while (next && count < ARRAY_SIZE(boot_params.e820_map));
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return boot_params.e820_entries = count;
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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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int err = -1;
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if (detect_memory_e820() > 0)
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err = 0;
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if (!detect_memory_e801())
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err = 0;
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if (!detect_memory_88())
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err = 0;
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return err;
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}
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