Red Bear OS — microkernel OS in Rust, based on Redox

Derivative of Redox OS (https://www.redox-os.org) adding:
- AMD GPU driver (amdgpu) via LinuxKPI compat layer
- ext4 filesystem support (ext4d scheme daemon)
- ACPI fixes for AMD bare metal (x2APIC, DMAR, IVRS, MCFG)
- Custom branding (hostname, os-release, boot identity)

Build system is full upstream Redox with RBOS overlay in local/.
Patches for kernel, base, and relibc are symlinked from local/patches/
and protected from make clean/distclean. Custom recipes live in
local/recipes/ with symlinks into the recipes/ search path.

Build:  make all CONFIG_NAME=redbear-full
Sync:   ./local/scripts/sync-upstream.sh

local/patches/base/P0-acpid-mcfg-ivrs.patch

@@ -0,0 +1,33 @@
+diff --git a/drivers/acpid/src/acpi.rs b/drivers/acpid/src/acpi.rs
+index 94a1eb17..3b376904 100644
+--- a/drivers/acpid/src/acpi.rs
++++ b/drivers/acpid/src/acpi.rs
+@@ -25,6 +25,14 @@ use amlserde::{AmlSerde, AmlSerdeValue};
+ 
+ #[cfg(target_arch = "x86_64")]
+ pub mod dmar;
++#[cfg(target_arch = "x86_64")]
++use self::dmar::Dmar;
++#[cfg(target_arch = "x86_64")]
++pub mod ivrs;
++#[cfg(target_arch = "x86_64")]
++pub mod mcfg;
++#[cfg(target_arch = "x86_64")]
++use self::{ivrs::Ivrs, mcfg::Mcfg};
+ use crate::aml_physmem::{AmlPageCache, AmlPhysMemHandler};
+ 
+ /// The raw SDT header struct, as defined by the ACPI specification.
+@@ -458,7 +466,12 @@ impl AcpiContext {
+         }
+ 
+         Fadt::init(&mut this);
+-        //TODO (hangs on real hardware): Dmar::init(&this);
++        // DMAR (Intel VT-d) init — previously disabled due to iterator bug (type_bytes copied
++        // instead of len_bytes in DmarRawIter). Safe to call now: on AMD systems, no DMAR table
++        // exists and this returns early with a warning.
++        Dmar::init(&this);
++        mcfg::Mcfg::init(&this);
++        ivrs::Ivrs::init(&this);
+ 
+         this
+     }