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>
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@ -22,6 +22,10 @@
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void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size)
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{
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u16 low_memory_kb;
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u16 ebda_kb;
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void *ebda;
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/* Skip in S3 resume path */
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if (acpi_is_wakeup_s3())
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return;
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@ -29,15 +33,20 @@ void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size)
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if (!low_memory_size || !ebda_segment || !ebda_size)
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return;
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/* clear BIOS DATA AREA */
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memset((void *)X86_BDA_BASE, 0, X86_BDA_SIZE);
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low_memory_kb = low_memory_size >> 10;
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ebda_kb = ebda_size >> 10;
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ebda = (void *)((uintptr_t)ebda_segment << 4);
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write16(X86_EBDA_LOWMEM, (low_memory_size >> 10));
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write16(X86_EBDA_SEGMENT, ebda_segment);
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/* clear BIOS DATA AREA */
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memset(X86_BDA_BASE, 0, X86_BDA_SIZE);
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/* Avoid unaligned write16() since it's undefined behavior */
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memcpy(X86_EBDA_LOWMEM, &low_memory_kb, sizeof(low_memory_kb));
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memcpy(X86_EBDA_SEGMENT, &ebda_segment, sizeof(ebda_segment));
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/* Set up EBDA */
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memset((void *)((uintptr_t)ebda_segment << 4), 0, ebda_size);
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write16((void *)((uintptr_t)ebda_segment << 4), (ebda_size >> 10));
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memset(ebda, 0, ebda_size);
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memcpy(ebda, &ebda_kb, sizeof(ebda_kb));
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}
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void setup_default_ebda(void)
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