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| author | H. Peter Anvin <hpa@zytor.com> | 2009-03-28 21:53:26 +0100 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2009-03-29 03:20:07 +0200 |
| commit | c549e71d073a6e9a4847497344db28a784061455 (patch) | |
| tree | 60c41d640ecf696d0534f744fafe8bf2023c4254 /arch | |
| parent | x86, setup: preemptively save/restore edi and ebp around INT 15 E820 (diff) | |
| download | linux-c549e71d073a6e9a4847497344db28a784061455.tar.xz linux-c549e71d073a6e9a4847497344db28a784061455.zip | |
x86, setup: ACPI 3, BIOS workaround for E820-probing code
Impact: ACPI 3 spec compliance, BIOS bug workaround
The ACPI 3 spec added another field to the E820 buffer -- which is
backwards incompatible, since it contains a validity bit.
Furthermore, there has been at least one report of a BIOS which
assumes that the buffer it is pointed at is the same buffer as for the
previous E820 call. Therefore, read the data into a temporary buffer
and copy the standard part of it if and only if the valid bit is set.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/boot/memory.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c index fcdb10add9c8..d5d2360763dc 100644 --- a/arch/x86/boot/memory.c +++ b/arch/x86/boot/memory.c @@ -2,6 +2,7 @@ * * Copyright (C) 1991, 1992 Linus Torvalds * Copyright 2007 rPath, Inc. - All Rights Reserved + * Copyright 2009 Intel Corporation; author H. Peter Anvin * * This file is part of the Linux kernel, and is made available under * the terms of the GNU General Public License version 2. @@ -16,6 +17,11 @@ #define SMAP 0x534d4150 /* ASCII "SMAP" */ +struct e820_ext_entry { + struct e820entry std; + u32 ext_flags; +} __attribute__((packed)); + static int detect_memory_e820(void) { int count = 0; @@ -23,9 +29,10 @@ static int detect_memory_e820(void) u32 size, id, edi; u8 err; struct e820entry *desc = boot_params.e820_map; + static struct e820_ext_entry buf; /* static so it is zeroed */ do { - size = sizeof(struct e820entry); + size = sizeof buf; /* Important: %edx and %esi are clobbered by some BIOSes, so they must be either used for the error output @@ -33,8 +40,8 @@ static int detect_memory_e820(void) is something out there clobbering %ebp and %edi, too. */ asm("pushl %%ebp; int $0x15; popl %%ebp; setc %0" : "=d" (err), "+b" (next), "=a" (id), "+c" (size), - "=D" (edi), "=m" (*desc) - : "D" (desc), "d" (SMAP), "a" (0xe820) + "=D" (edi), "+m" (buf) + : "D" (&buf), "d" (SMAP), "a" (0xe820) : "esi"); /* BIOSes which terminate the chain with CF = 1 as opposed @@ -53,8 +60,14 @@ static int detect_memory_e820(void) break; } + /* ACPI 3.0 added the extended flags support. If bit 0 + in the extended flags is zero, we're supposed to simply + ignore the entry -- a backwards incompatible change! */ + if (size > 20 && !(buf.ext_flags & 1)) + continue; + + *desc++ = buf.std; count++; - desc++; } while (next && count < ARRAY_SIZE(boot_params.e820_map)); return boot_params.e820_entries = count; |