Commit-ID: 1b3a62643660020cdc68e6139a010c06e8fc96c7
Gitweb: https://git.kernel.org/tip/1b3a62643660020cdc68e6139a010c06e8fc96c7
Author: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
AuthorDate: Wed, 1 Aug 2018 16:32:25 +0300
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 2 Aug 2018 14:22:22 +0200
x86/boot/compressed/64: Validate trampoline placement against E820
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: 3548e131ec6a ("x86/boot/compressed/64: Find a place for 32-bit trampoline")
Reported-by: Dmitry Malkin <d.malkin@xxxxxxxxxxxxxxxxxxxxx>
Reported-by: youling 257 <youling257@xxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Link: https://lkml.kernel.org/r/20180801133225.38121-1-kirill.shutemov@xxxxxxxxxxxxxxx
---
arch/x86/boot/compressed/pgtable_64.c | 73 ++++++++++++++++++++++++++---------
1 file changed, 55 insertions(+), 18 deletions(-)
diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index 8c5107545251..9e2157371491 100644
--- a/arch/x86/boot/compressed/pgtable_64.c
+++ b/arch/x86/boot/compressed/pgtable_64.c
@@ -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;
--
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