From e215f9d62c7b81e97e5cf790edc86784f8011a4a Mon Sep 17 00:00:00 2001
From: Berkus Decker <berkus+github@metta.systems>
Date: Fri, 26 Feb 2021 00:16:42 +0200
Subject: [PATCH] [wip] add to-kernel-space/from-kernel-space address
 conversion

---
 nucleus/src/arch/aarch64/memory/addr/mod.rs         |  5 +++++
 nucleus/src/arch/aarch64/memory/addr/phys_addr.rs   | 12 +++++++++++-
 nucleus/src/arch/aarch64/memory/addr/virt_addr.rs   | 12 +++++++++++-
 nucleus/src/arch/aarch64/memory/mmu-experimental.rs |  4 ----
 4 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/nucleus/src/arch/aarch64/memory/addr/mod.rs b/nucleus/src/arch/aarch64/memory/addr/mod.rs
index 54076b1..3988351 100644
--- a/nucleus/src/arch/aarch64/memory/addr/mod.rs
+++ b/nucleus/src/arch/aarch64/memory/addr/mod.rs
@@ -10,3 +10,8 @@ mod virt_addr;
 pub use asid::*;
 pub use phys_addr::*;
 pub use virt_addr::*;
+
+// @todo Check largest VA supported, calculate physical_memory_offset
+// @todo Keep in mind amount of physical memory present, the following
+// @todo will only work for 1Gb board:
+pub const PHYSICAL_MEMORY_OFFSET: u64 = 0xffff_8000_0000_0000; // Last 1GiB of VA space
diff --git a/nucleus/src/arch/aarch64/memory/addr/phys_addr.rs b/nucleus/src/arch/aarch64/memory/addr/phys_addr.rs
index 4e29e58..fd9afd7 100644
--- a/nucleus/src/arch/aarch64/memory/addr/phys_addr.rs
+++ b/nucleus/src/arch/aarch64/memory/addr/phys_addr.rs
@@ -4,7 +4,10 @@
  */
 
 use {
-    crate::mm::{align_down, align_up},
+    crate::{
+        memory::VirtAddr,
+        mm::{align_down, align_up},
+    },
     bit_field::BitField,
     core::{
         convert::{From, Into},
@@ -97,6 +100,13 @@ impl PhysAddr {
     {
         self.aligned_down(align) == self
     }
+
+    /// Convert physical memory address into a kernel virtual address.
+    pub fn user_to_kernel(&self) -> VirtAddr {
+        use super::PHYSICAL_MEMORY_OFFSET;
+        assert!(self.0 < !PHYSICAL_MEMORY_OFFSET); // Can't have phys address over 1GiB then
+        VirtAddr::new(self.0 + PHYSICAL_MEMORY_OFFSET)
+    }
 }
 
 impl fmt::Debug for PhysAddr {
diff --git a/nucleus/src/arch/aarch64/memory/addr/virt_addr.rs b/nucleus/src/arch/aarch64/memory/addr/virt_addr.rs
index 4357f68..013f182 100644
--- a/nucleus/src/arch/aarch64/memory/addr/virt_addr.rs
+++ b/nucleus/src/arch/aarch64/memory/addr/virt_addr.rs
@@ -4,7 +4,10 @@
  */
 
 use {
-    crate::mm::{align_down, align_up},
+    crate::{
+        memory::PhysAddr,
+        mm::{align_down, align_up},
+    },
     bit_field::BitField,
     core::{
         convert::{From, Into, TryInto},
@@ -158,6 +161,13 @@ impl VirtAddr {
     pub fn l0_index(&self) -> u9 {
         u9::new(((self.0 >> 12 >> 9 >> 9 >> 9) & 0o777).try_into().unwrap())
     }
+
+    /// Convert kernel-space virtual address into a physical memory address.
+    pub fn kernel_to_user(&self) -> PhysAddr {
+        use super::PHYSICAL_MEMORY_OFFSET;
+        assert!(self.0 > PHYSICAL_MEMORY_OFFSET);
+        PhysAddr::new(self.0 - PHYSICAL_MEMORY_OFFSET)
+    }
 }
 
 impl fmt::Debug for VirtAddr {
diff --git a/nucleus/src/arch/aarch64/memory/mmu-experimental.rs b/nucleus/src/arch/aarch64/memory/mmu-experimental.rs
index e970ab6..2f15924 100644
--- a/nucleus/src/arch/aarch64/memory/mmu-experimental.rs
+++ b/nucleus/src/arch/aarch64/memory/mmu-experimental.rs
@@ -1,7 +1,3 @@
-// Check largest VA supported, calculate physical_memory_offset
-//
-const PHYSICAL_MEMORY_OFFSET: u64 = 0xffff_8000_0000_0000; // Last 1GiB of VA space
-
 // AArch64:
 // Table D4-8-2021: check supported granule sizes, select alloc policy based on results.
 // TTBR_ELx is the pdbr for specific page tables