From ea16a1b55111c5a1deae97cbe16b9b27be28b7e7 Mon Sep 17 00:00:00 2001
From: vasilito <adminpupkin@gmail.com>
Date: Thu, 9 Jul 2026 12:04:39 +0300
Subject: [PATCH] acpi: map FACS before parsing (not identity-mapped on all
 firmwares)

---
 src/acpi/mod.rs | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/src/acpi/mod.rs b/src/acpi/mod.rs
index 2ab2e17168..0ff841214b 100644
--- a/src/acpi/mod.rs
+++ b/src/acpi/mod.rs
@@ -178,26 +178,23 @@ pub unsafe fn init(already_supplied_rsdp: Option<NonNull<u8>>) {
             //
             // The FACS is found via the FADT's x_firmware_ctrl
             // field (64-bit) or firmware_ctrl field (32-bit).
-            // The FADT parser caches the FACS address. We use
-            // the FADT's x_firmware_ctrl to find the FACS SDT.
-            let facs_addr = fadt::x_firmware_ctrl();
+            // The FADT parser caches the FACS address. We map the
+            // FACS here because it is not listed in the RSDT/XSDT
+            // and therefore was not mapped during table discovery.
+            const FACS_MIN_SIZE: usize = 64;
+            let mut facs_addr = fadt::x_firmware_ctrl();
+            if facs_addr == 0 {
+                facs_addr = fadt::firmware_ctrl() as u64;
+            }
             if facs_addr != 0 {
-                // SAFETY: The FACS address is a physical
-                // address stored in the FADT. The boot-time page
-                // table maps the FACS into the kernel's address
-                // space (firmware tables are below 4GB on x86_64).
-                let facs_sdt = unsafe { &*(facs_addr as *const Sdt) };
+                let facs_phys = PhysicalAddress::new(facs_addr as usize);
+                map_linearly(facs_phys, FACS_MIN_SIZE, &mut KernelMapper::lock_rw());
+                let facs_sdt = unsafe {
+                    &*(RmmA::phys_to_virt(facs_phys).data() as *const Sdt)
+                };
                 facs::init(facs_sdt);
             } else {
-                let facs_addr = fadt::firmware_ctrl() as u64;
-                if facs_addr != 0 {
-                    // SAFETY: same as above.
-                    let facs_sdt =
-                        unsafe { &*(facs_addr as *const Sdt) };
-                    facs::init(facs_sdt);
-                } else {
-                    warn!("ACPI: no FACS found (neither x_firmware_ctrl nor firmware_ctrl), S3 resume path disabled");
-                }
+                warn!("ACPI: no FACS found (neither x_firmware_ctrl nor firmware_ctrl), S3 resume path disabled");
             }
         } else {
             error!("NO RSDP FOUND");