device/acpi: More correctness fixes

Author: marv7000

kernel/src/arch/x86_64/system/acpi.rs

@@ -102,11 +102,11 @@ impl PortIoAccess {
         unsafe {
             asm::write32(
                 0xCF8,
-                (addr.bus as u32) << 16
-                    | (addr.slot as u32) << 11
-                    | (addr.function as u32) << 8
-                    | (offset & 0xFC)
-                    | 1 << 31,
+                1 << 31
+                    | (addr.bus as u32) << 16
+                    | (addr.slot as u32 & 0x1F) << 11
+                    | (addr.function as u32 & 0x7) << 8
+                    | (offset & 0xFC),
             );
         }
     }

kernel/src/device/acpi/mcfg.rs

@@ -7,8 +7,8 @@ use crate::{
 };
 use alloc::{boxed::Box, vec::Vec};
 use uacpi_sys::{
-    UACPI_STATUS_OK, acpi_mcfg, acpi_mcfg_allocation, acpi_sdt_hdr, uacpi_table,
-    uacpi_table_find_by_signature, uacpi_table_unref,
+    UACPI_STATUS_OK, acpi_mcfg, acpi_mcfg_allocation, uacpi_table, uacpi_table_find_by_signature,
+    uacpi_table_unref,
 };
 
 #[task(
@@ -30,7 +30,7 @@ pub fn MCFG_STAGE() {
         let mcfg_ptr = table.__bindgen_anon_1.ptr as *const uacpi_sys::acpi_mcfg;
         let mcfg = mcfg_ptr.read_unaligned();
 
-        let entry_count = (mcfg.hdr.length as usize - size_of::<acpi_sdt_hdr>())
+        let entry_count = (mcfg.hdr.length as usize).saturating_sub(size_of::<acpi_mcfg>())
             / size_of::<acpi_mcfg_allocation>();
 
         let mut accesses = Vec::new();

kernel/src/device/acpi/mod.rs

@@ -8,15 +8,24 @@ mod uacpi;
 static RSDP_ADDRESS: Once<PhysAddr> = Once::new();
 
 #[task(
-    name = "device.acpi.tables",
+    name = "device.acpi.root",
     depends = [crate::memory::MEMORY_STAGE],
 )]
-pub fn TABLES_STAGE() {
+pub fn ACPI_ROOT() -> bool {
     match BootInfo::get().rsdp_addr {
-        Some(rsdp) => unsafe { RSDP_ADDRESS.init(rsdp) },
-        None => panic!("No RSDP available, unable to initialize the ACPI subsystem!"),
-    };
+        Some(x) => {
+            unsafe { RSDP_ADDRESS.init(x) };
+            true
+        }
+        None => false,
+    }
+}
 
+#[task(
+    name = "device.acpi.tables",
+    depends = [ACPI_ROOT],
+)]
+pub fn TABLES_STAGE() {
     // Get an early table window so we can initialize e.g. HPET and MADT.
     let early_mem = Box::leak(Box::<[u8]>::new_uninit_slice(4096));