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arch/x86: Fix undefined behavior 

Fixes report found by undefined behavior sanitizer. Dereferencing a
pointer that is not aligned to the size of access is undefined behavior.
Switch to memcpy() for unaligned write to EBDA_LOWMEM. Change other
write16()s in setup_ebda() to memcpy() for consistency.

Change-Id: I79814bd47a14ec59d84068b11d094dc2531995d9
Signed-off-by: Ryan Salsamendi <rsalsamendi@hotmail.com>
Reviewed-on: https://review.coreboot.org/20132
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com>
This commit is contained in:
Ryan Salsamendi 2017-06-09 12:01:39 -07:00 committed by Patrick Georgi
parent cde2bdf496
commit f0b0712023
1 changed files with 15 additions and 6 deletions
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21
src/arch/x86/ebda.c
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@ -22,6 +22,10 @@
void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size) void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size)
{ {
u16 low_memory_kb;
u16 ebda_kb;
void *ebda;
/* Skip in S3 resume path */ /* Skip in S3 resume path */
if (acpi_is_wakeup_s3()) if (acpi_is_wakeup_s3())
return; return;
@ -29,15 +33,20 @@ void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size)
if (!low_memory_size || !ebda_segment || !ebda_size) if (!low_memory_size || !ebda_segment || !ebda_size)
return; return;
/* clear BIOS DATA AREA */ low_memory_kb = low_memory_size >> 10;
memset((void *)X86_BDA_BASE, 0, X86_BDA_SIZE); ebda_kb = ebda_size >> 10;
ebda = (void *)((uintptr_t)ebda_segment << 4);
write16(X86_EBDA_LOWMEM, (low_memory_size >> 10)); /* clear BIOS DATA AREA */
write16(X86_EBDA_SEGMENT, ebda_segment); memset(X86_BDA_BASE, 0, X86_BDA_SIZE);
/* Avoid unaligned write16() since it's undefined behavior */
memcpy(X86_EBDA_LOWMEM, &low_memory_kb, sizeof(low_memory_kb));
memcpy(X86_EBDA_SEGMENT, &ebda_segment, sizeof(ebda_segment));
/* Set up EBDA */ /* Set up EBDA */
memset((void *)((uintptr_t)ebda_segment << 4), 0, ebda_size); memset(ebda, 0, ebda_size);
write16((void *)((uintptr_t)ebda_segment << 4), (ebda_size >> 10)); memcpy(ebda, &ebda_kb, sizeof(ebda_kb));
} }
void setup_default_ebda(void) void setup_default_ebda(void)