acpi: Parse the AML tables after free memory pool has been setup.

- Dont call parseAMLTables() when all of the other ACPI tables are
  parsed as it requires too much memory so move the parse to the
  DeviceManager init().

- Convert ACPI from a struct to a class since there should only be
  a singleton instance anyway.

- Reduce the stack size from 6 pages down to 4. Also reduce the
  initial heap set in the linker script from 2048 pages (8MB) down
  to 64 pages (256k).

acpitest/main.swift

@@ -72,7 +72,7 @@ func loadData(_ fileSet: Int) -> ACPI {
     var testDir = Bundle.main.resourcePath!
     testDir.append("/acpitest.xctest/Contents/Resources/")
 
-    var acpi = ACPI()
+    let acpi = ACPI()
     for file in files[fileSet] {
         //print("Filename:", file)
         let data = openOrQuit(filename: testDir + "/" + file)

kernel/devices/acpi/acpi.swift

@@ -113,7 +113,7 @@ struct RSDP2: CustomStringConvertible {
 }
 
 
-struct ACPI {
+final class ACPI {
     private(set) var mcfg: MCFG?
     private(set) var facp: FACP?
     private(set) var madt: MADT?
@@ -135,13 +135,11 @@ struct ACPI {
             parseEntry(rawSDTPtr: rawSDTPtr, vendor: vendor, product: product)
         }
 
-        print("Parsing AML")
         if dsdt == nil, let dsdtAddr = facp?.dsdtAddress {
             print("Found DSDT address in FACP: 0x\(asHex(dsdtAddr.value))")
             parseEntry(rawSDTPtr: mkSDTPtr(dsdtAddr),
                        vendor: vendor, product: product)
         }
-        globalObjects = parseAMLTables()
     }
 
 
@@ -150,7 +148,8 @@ struct ACPI {
     }
 
 
-    mutating func parseAMLTables() -> ACPIGlobalObjects? {
+    func parseAMLTables() {
+        print("Parsing AML")
         guard let ptr = dsdt else {
             fatalError("ACPI: No valid DSDT found")
         }
@@ -171,11 +170,10 @@ struct ACPI {
         //parser.parseMethods()
         globalObjects = parser.acpiGlobalObjects
         print("End of AML code")
-        return acpiGlobalObjects
     }
 
 
-    mutating func parseEntry(rawSDTPtr: UnsafeRawPointer, vendor: String,
+    func parseEntry(rawSDTPtr: UnsafeRawPointer, vendor: String,
         product: String) {
 
         let signature = tableSignature(ptr: rawSDTPtr)

kernel/devices/devicemanager.swift

@@ -117,6 +117,7 @@ final class DeviceManager {
 
 
     init(acpiTables: ACPI) {
+        acpiTables.parseAMLTables()
         guard let (sb, sbFullName) = acpiTables.globalObjects.getGlobalObject(currentScope: AMLNameString("\\"),
                                                                         name: AMLNameString("_SB")) else {
             fatalError("No \\_SB system bus node")

linker.script

@@ -3,7 +3,7 @@ OUTPUT_FORMAT("elf64-x86-64", "elf64-x86-64", "elf64-x86-64")
 
 PAGE_SIZE = 0x1000;
 /* Needs to be bigger for DEBUG mode, can be 2 for non debug */
-STACK_SIZE = 6 * PAGE_SIZE;
+STACK_SIZE = 4 * PAGE_SIZE;
 
 PHDRS {
       text   PT_LOAD FLAGS(5);  /* R_E */
@@ -102,7 +102,7 @@ SECTIONS {
     . += PAGE_SIZE;
     _ist1_stack_top = .;
     _heap_start = .;
-    . += PAGE_SIZE * 2048;
+    . += PAGE_SIZE * 64;
     _heap_end = .;
 
     _bss_end = .;