OvmfPkg/LoongArchVirt: Fix ACPI table walk in reset library

The DXE ACPI GED reset library locates the FADT by walking the
RSDT and XSDT from the RSDP. The existing code assumed that both
RSDP address fields were non-zero and that every table entry was a
valid ACPI table address.

That assumption is unsafe once NULL pointer detection is enabled. A
zero RSDT/XSDT address, or a zero table entry, can be converted into a
pointer to address 0 and then dereferenced while checking the table
signature.

RSDT entries are 32-bit physical addresses, while XSDT entries are
64-bit physical addresses. Parse those entry arrays separately so the
XSDT path does not split each 64-bit entry into two bogus 32-bit
values. Use ReadUnaligned64() for XSDT entries because the ACPI table
header size does not guarantee natural 8-byte alignment for the entry
array on all architectures.

Update the FADT discovery path to:
- skip RSDT scanning when RsdtAddress is zero,
- skip XSDT scanning when XsdtAddress is zero,
- ignore zero RSDT/XSDT entries,
- parse XSDT entries as UINT64 addresses, and
- read XSDT entries with unaligned-safe access.

This prevents the reset library from dereferencing address 0 while
preserving the existing behavior of using the first FADT found through
RSDT or XSDT.

Signed-off-by: Dongyan Qian <qiandongyan@loongson.cn>

0 files changed, 0 insertions, 0 deletions