x86: fix memmap=exactmap boot argument

Backport of d6be118a97ce51ca84035270f91c2bccecbfac5f by Chuck Ebbert

When using kdump modifying the e820 map is yielding strange results.

For example starting with

 BIOS-provided physical RAM map:
 BIOS-e820: 0000000000000100 - 0000000000093400 (usable)
 BIOS-e820: 0000000000093400 - 00000000000a0000 (reserved)
 BIOS-e820: 0000000000100000 - 000000003fee0000 (usable)
 BIOS-e820: 000000003fee0000 - 000000003fef3000 (ACPI data)
 BIOS-e820: 000000003fef3000 - 000000003ff80000 (ACPI NVS)
 BIOS-e820: 000000003ff80000 - 0000000040000000 (reserved)
 BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
 BIOS-e820: 00000000fec00000 - 00000000fec10000 (reserved)
 BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
 BIOS-e820: 00000000ff000000 - 0000000100000000 (reserved)

and booting with args

memmap=exactmap memmap=640K@0K memmap=5228K@16384K memmap=125188K@22252K memmap=76K#1047424K memmap=564K#1047500K

resulted in:

 user-defined physical RAM map:
 user: 0000000000000000 - 0000000000093400 (usable)
 user: 0000000000093400 - 00000000000a0000 (reserved)
 user: 0000000000100000 - 000000003fee0000 (usable)
 user: 000000003fee0000 - 000000003fef3000 (ACPI data)
 user: 000000003fef3000 - 000000003ff80000 (ACPI NVS)
 user: 000000003ff80000 - 0000000040000000 (reserved)
 user: 00000000e0000000 - 00000000f0000000 (reserved)
 user: 00000000fec00000 - 00000000fec10000 (reserved)
 user: 00000000fee00000 - 00000000fee01000 (reserved)
 user: 00000000ff000000 - 0000000100000000 (reserved)

But should have resulted in:

 user-defined physical RAM map:
 user: 0000000000000000 - 00000000000a0000 (usable)
 user: 0000000001000000 - 000000000151b000 (usable)
 user: 00000000015bb000 - 0000000008ffc000 (usable)
 user: 000000003fee0000 - 000000003ff80000 (ACPI data)

This is happening because of an improper usage of strcmp() in the
e820 parsing code.  The strcmp() always returns !0 and never resets the
value for e820.nr_map and returns an incorrect user-defined map.

This patch fixes the problem.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kernel/e820_32.c b/arch/x86/kernel/e820_32.c
index ed733e7cf4e611c454f9ea622c9322919aa624b4..a540c4ee275fe1401c8cd013e33d4b28b8cc1f3c 100644 (file)
--- a/arch/x86/kernel/e820_32.c
+++ b/arch/x86/kernel/e820_32.c
@@ -697,7 +697,7 @@ static int __init parse_memmap(char *arg)
        if (!arg)
                return -EINVAL;
 
-       if (strcmp(arg, "exactmap") == 0) {
+       if (strncmp(arg, "exactmap", 8) == 0) {
 #ifdef CONFIG_CRASH_DUMP
                /* If we are doing a crash dump, we
                 * still need to know the real mem

diff --git a/arch/x86/kernel/e820_64.c b/arch/x86/kernel/e820_64.c
index 124480c0008dd2a5e348cd2db7b928ff13d3aa41..4da8e2bea8b407d71572051571bf0f4c206b1616 100644 (file)
--- a/arch/x86/kernel/e820_64.c
+++ b/arch/x86/kernel/e820_64.c
@@ -776,7 +776,7 @@ static int __init parse_memmap_opt(char *p)
        char *oldp;
        unsigned long long start_at, mem_size;
 
-       if (!strcmp(p, "exactmap")) {
+       if (!strncmp(p, "exactmap", 8)) {
 #ifdef CONFIG_CRASH_DUMP
                /*
                 * If we are doing a crash dump, we still need to know