Move memory layout helpers to new module.

Bug: 223166344
Test: atest vmbase_example.integration_test
Change-Id: I2e819594bc6110783b5e64fa6485052b0f01e062
diff --git a/vmbase/example/src/layout.rs b/vmbase/example/src/layout.rs
new file mode 100644
index 0000000..9cf1a69
--- /dev/null
+++ b/vmbase/example/src/layout.rs
@@ -0,0 +1,123 @@
+// Copyright 2022, The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Memory layout.
+
+use aarch64_paging::paging::{MemoryRegion, VirtualAddress};
+use core::ops::Range;
+use vmbase::println;
+
+/// The first 1 GiB of memory are used for MMIO.
+pub const DEVICE_REGION: MemoryRegion = MemoryRegion::new(0, 0x40000000);
+
+/// Memory reserved for the DTB.
+pub fn dtb_range() -> Range<VirtualAddress> {
+    unsafe {
+        VirtualAddress(&dtb_begin as *const u8 as usize)
+            ..VirtualAddress(&dtb_end as *const u8 as usize)
+    }
+}
+
+/// Executable code.
+pub fn text_range() -> Range<VirtualAddress> {
+    unsafe {
+        VirtualAddress(&text_begin as *const u8 as usize)
+            ..VirtualAddress(&text_end as *const u8 as usize)
+    }
+}
+
+/// Read-only data.
+pub fn rodata_range() -> Range<VirtualAddress> {
+    unsafe {
+        VirtualAddress(&rodata_begin as *const u8 as usize)
+            ..VirtualAddress(&rodata_end as *const u8 as usize)
+    }
+}
+
+/// Initialised writable data.
+pub fn data_range() -> Range<VirtualAddress> {
+    unsafe {
+        VirtualAddress(&data_begin as *const u8 as usize)
+            ..VirtualAddress(&data_end as *const u8 as usize)
+    }
+}
+
+/// Zero-initialised writable data.
+pub fn bss_range() -> Range<VirtualAddress> {
+    unsafe {
+        VirtualAddress(&bss_begin as *const u8 as usize)
+            ..VirtualAddress(&bss_end as *const u8 as usize)
+    }
+}
+
+/// Writable data region for the stack.
+pub fn boot_stack_range() -> Range<VirtualAddress> {
+    unsafe {
+        VirtualAddress(&boot_stack_begin as *const u8 as usize)
+            ..VirtualAddress(&boot_stack_end as *const u8 as usize)
+    }
+}
+
+/// Writable data, including the stack.
+pub fn writable_region() -> MemoryRegion {
+    unsafe {
+        MemoryRegion::new(&data_begin as *const u8 as usize, &boot_stack_end as *const u8 as usize)
+    }
+}
+
+fn data_load_address() -> VirtualAddress {
+    unsafe { VirtualAddress(&data_lma as *const u8 as usize) }
+}
+
+pub fn print_addresses() {
+    let dtb = dtb_range();
+    println!("dtb:        {}..{} ({} bytes)", dtb.start, dtb.end, dtb.end - dtb.start);
+    let text = text_range();
+    println!("text:       {}..{} ({} bytes)", text.start, text.end, text.end - text.start);
+    let rodata = rodata_range();
+    println!("rodata:     {}..{} ({} bytes)", rodata.start, rodata.end, rodata.end - rodata.start);
+    let data = data_range();
+    println!(
+        "data:       {}..{} ({} bytes, loaded at {})",
+        data.start,
+        data.end,
+        data.end - data.start,
+        data_load_address(),
+    );
+    let bss = bss_range();
+    println!("bss:        {}..{} ({} bytes)", bss.start, bss.end, bss.end - bss.start);
+    let boot_stack = boot_stack_range();
+    println!(
+        "boot_stack: {}..{} ({} bytes)",
+        boot_stack.start,
+        boot_stack.end,
+        boot_stack.end - boot_stack.start
+    );
+}
+
+extern "C" {
+    static dtb_begin: u8;
+    static dtb_end: u8;
+    static text_begin: u8;
+    static text_end: u8;
+    static rodata_begin: u8;
+    static rodata_end: u8;
+    static data_begin: u8;
+    static data_end: u8;
+    static data_lma: u8;
+    static bss_begin: u8;
+    static bss_end: u8;
+    static boot_stack_begin: u8;
+    static boot_stack_end: u8;
+}