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Diffstat (limited to 'arch/x86/include/asm/bios_ebda.h')
-rw-r--r--arch/x86/include/asm/bios_ebda.h28
1 files changed, 26 insertions, 2 deletions
diff --git a/arch/x86/include/asm/bios_ebda.h b/arch/x86/include/asm/bios_ebda.h
index 3c75210..aa6a317 100644
--- a/arch/x86/include/asm/bios_ebda.h
+++ b/arch/x86/include/asm/bios_ebda.h
@@ -4,16 +4,40 @@
#include <asm/io.h>
/*
- * there is a real-mode segmented pointer pointing to the
- * 4K EBDA area at 0x40E.
+ * Returns physical address of EBDA. Returns 0 if there is no EBDA.
*/
static inline unsigned int get_bios_ebda(void)
{
+ /*
+ * There is a real-mode segmented pointer pointing to the
+ * 4K EBDA area at 0x40E.
+ */
unsigned int address = *(unsigned short *)phys_to_virt(0x40E);
address <<= 4;
return address; /* 0 means none */
}
+/*
+ * Return the sanitized length of the EBDA in bytes, if it exists.
+ */
+static inline unsigned int get_bios_ebda_length(void)
+{
+ unsigned int address;
+ unsigned int length;
+
+ address = get_bios_ebda();
+ if (!address)
+ return 0;
+
+ /* EBDA length is byte 0 of the EBDA (stored in KiB) */
+ length = *(unsigned char *)phys_to_virt(address);
+ length <<= 10;
+
+ /* Trim the length if it extends beyond 640KiB */
+ length = min_t(unsigned int, (640 * 1024) - address, length);
+ return length;
+}
+
void reserve_ebda_region(void);
#ifdef CONFIG_X86_CHECK_BIOS_CORRUPTION