Kernel+LibACPI: Move table validation code to LibACPI

It will be used outside of the kernel. While at it clean the function
up a bit to make it a little more readable.

Kernel/CMakeLists.txt

@@ -637,6 +637,10 @@ set(AK_SOURCES
     ../AK/UUID.cpp
 )
 
+set(ACPI_SOURCES
+    ../Userland/Libraries/LibACPI/Table.cpp
+)
+
 set(DT_SOURCES
     ../Userland/Libraries/LibDeviceTree/DeviceTree.cpp
     ../Userland/Libraries/LibDeviceTree/FlattenedDeviceTree.cpp
@@ -840,6 +844,7 @@ set(SOURCES
     ${KERNEL_SOURCES}
     ${GENERATED_SOURCES}
     ${AK_SOURCES}
+    ${ACPI_SOURCES}
     ${DT_SOURCES}
     ${EDID_SOURCES}
     ${ELF_SOURCES}

Kernel/Firmware/ACPI/Parser.cpp

@@ -21,6 +21,7 @@
 #include <Kernel/Library/StdLib.h>
 #include <Kernel/Memory/TypedMapping.h>
 #include <Kernel/Sections.h>
+#include <LibACPI/Table.h>
 
 namespace Kernel::ACPI {
 
@@ -120,8 +121,6 @@ void Parser::enumerate_static_tables(Function<void(StringView, PhysicalAddress,
     }
 }
 
-static bool validate_table(::ACPI::Structures::SDTHeader const&, size_t length);
-
 UNMAP_AFTER_INIT void Parser::locate_static_data()
 {
     locate_main_system_description_table();
@@ -352,7 +351,7 @@ UNMAP_AFTER_INIT void Parser::initialize_main_system_description_table()
 
     auto sdt = Memory::map_typed<::ACPI::Structures::SDTHeader>(m_main_system_description_table, length).release_value_but_fixme_should_propagate_errors();
 
-    dmesgln("ACPI: Main Description Table valid? {}", validate_table(*sdt, length));
+    dmesgln("ACPI: Main Description Table valid? {}", ::ACPI::validate_table(*sdt));
 
     if (m_xsdt_supported) {
         auto& xsdt = (::ACPI::Structures::XSDT const&)*sdt;
@@ -403,15 +402,4 @@ UNMAP_AFTER_INIT Parser::Parser(PhysicalAddress rsdp, PhysicalAddress fadt, Inte
     locate_static_data();
 }
 
-static bool validate_table(::ACPI::Structures::SDTHeader const& v_header, size_t length)
-{
-    u8 checksum = 0;
-    auto* sdt = (u8 const*)&v_header;
-    for (size_t i = 0; i < length; i++)
-        checksum += sdt[i];
-    if (checksum == 0)
-        return true;
-    return false;
-}
-
 }

Userland/Libraries/LibACPI/CMakeLists.txt

@@ -0,0 +1,4 @@
+set(SOURCES
+    Table.cpp
+)
+serenity_lib(LibACPI acpi)

Userland/Libraries/LibACPI/Table.cpp

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2026, Undefine <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include "Table.h"
+#include <AK/BitCast.h>
+
+namespace ACPI {
+
+bool validate_table(::ACPI::Structures::SDTHeader const& header)
+{
+    auto const* sdt = reinterpret_cast<u8 const*>(&header);
+
+    u8 checksum = 0;
+    for (size_t i = 0; i < header.length; i++)
+        checksum += sdt[i];
+
+    return checksum == 0;
+}
+
+}

Userland/Libraries/LibACPI/Table.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2026, Undefine <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include "Definitions.h"
+
+namespace ACPI {
+
+bool validate_table(::ACPI::Structures::SDTHeader const& header);
+
+}