From 18f61c542724713f111deb1292d16f0eb33b6361 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Sun, 29 Oct 2023 21:35:11 +0200
Subject: [PATCH] Kernel: Fix ACPI DSDT address

Read x_dsdt address only if fadt's length contains it. Bochs seems
to have version 1 fadt without the x_* fields.
---
 kernel/kernel/ACPI.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/kernel/ACPI.cpp b/kernel/kernel/ACPI.cpp
index 072f337a..86ac0a3a 100644
--- a/kernel/kernel/ACPI.cpp
+++ b/kernel/kernel/ACPI.cpp
@@ -211,7 +211,10 @@ namespace Kernel
 			if (memcmp(header->signature, "FACP", 4) == 0)
 			{
 				auto* fadt = (FADT*)header;
-				paddr_t dsdt_paddr = fadt->x_dsdt;
+
+				paddr_t dsdt_paddr = 0;
+				if (fadt->length > 140) // 140 is the offset of x_dsdt
+					dsdt_paddr = fadt->x_dsdt;
 				if (dsdt_paddr == 0 || !PageTable::is_valid_pointer(dsdt_paddr))
 					dsdt_paddr = fadt->dsdt;