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x86/boot/compressed/64: Validate trampoline placement against E820

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There were two report of boot failure cased by trampoline placed into
a reserved memory region. It can happen on machines that don't report
EBDA correctly.

Fix the problem by re-validating the found address against the E820 table.
If the address is in a reserved area, find the next usable region below the
initial address.

Fixes: 3548e131ec ("x86/boot/compressed/64: Find a place for 32-bit trampoline")
Reported-by: Dmitry Malkin <d.malkin@real-time-systems.com>
Reported-by: youling 257 <youling257@gmail.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20180801133225.38121-1-kirill.shutemov@linux.intel.com
This commit is contained in:
Kirill A. Shutemov 2018-08-01 16:32:25 +03:00 committed by Thomas Gleixner
parent 6b47037682
commit 1b3a626436
1 changed files with 55 additions and 18 deletions
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73
arch/x86/boot/compressed/pgtable_64.c
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@ -1,3 +1,4 @@
#include <asm/e820/types.h>
#include <asm/processor.h>
#include "pgtable.h"
#include "../string.h"
@ -34,10 +35,62 @@ unsigned long *trampoline_32bit __section(.data);
extern struct boot_params *boot_params;
int cmdline_find_option_bool(const char *option);
static unsigned long find_trampoline_placement(void)
{
unsigned long bios_start, ebda_start;
unsigned long trampoline_start;
struct boot_e820_entry *entry;
int i;
/*
* Find a suitable spot for the trampoline.
* This code is based on reserve_bios_regions().
*/
ebda_start = *(unsigned short *)0x40e << 4;
bios_start = *(unsigned short *)0x413 << 10;
if (bios_start < BIOS_START_MIN || bios_start > BIOS_START_MAX)
bios_start = BIOS_START_MAX;
if (ebda_start > BIOS_START_MIN && ebda_start < bios_start)
bios_start = ebda_start;
bios_start = round_down(bios_start, PAGE_SIZE);
/* Find the first usable memory region under bios_start. */
for (i = boot_params->e820_entries - 1; i >= 0; i--) {
entry = &boot_params->e820_table[i];
/* Skip all entries above bios_start. */
if (bios_start <= entry->addr)
continue;
/* Skip non-RAM entries. */
if (entry->type != E820_TYPE_RAM)
continue;
/* Adjust bios_start to the end of the entry if needed. */
if (bios_start > entry->addr + entry->size)
bios_start = entry->addr + entry->size;
/* Keep bios_start page-aligned. */
bios_start = round_down(bios_start, PAGE_SIZE);
/* Skip the entry if it's too small. */
if (bios_start - TRAMPOLINE_32BIT_SIZE < entry->addr)
continue;
break;
}
/* Place the trampoline just below the end of low memory */
return bios_start - TRAMPOLINE_32BIT_SIZE;
}
struct paging_config paging_prepare(void *rmode)
{
struct paging_config paging_config = {};
unsigned long bios_start, ebda_start;
/* Initialize boot_params. Required for cmdline_find_option_bool(). */
boot_params = rmode;
@ -61,23 +114,7 @@ struct paging_config paging_prepare(void *rmode)
paging_config.l5_required = 1;
}
/*
* Find a suitable spot for the trampoline.
* This code is based on reserve_bios_regions().
*/
ebda_start = *(unsigned short *)0x40e << 4;
bios_start = *(unsigned short *)0x413 << 10;
if (bios_start < BIOS_START_MIN || bios_start > BIOS_START_MAX)
bios_start = BIOS_START_MAX;
if (ebda_start > BIOS_START_MIN && ebda_start < bios_start)
bios_start = ebda_start;
/* Place the trampoline just below the end of low memory, aligned to 4k */
paging_config.trampoline_start = bios_start - TRAMPOLINE_32BIT_SIZE;
paging_config.trampoline_start = round_down(paging_config.trampoline_start, PAGE_SIZE);
paging_config.trampoline_start = find_trampoline_placement();
trampoline_32bit = (unsigned long *)paging_config.trampoline_start;