From 26c86f8242031e44365ebe67260fca7b88442b92 Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jackpot51@gmail.com>
Date: Wed, 17 Aug 2016 19:06:33 -0600
Subject: [PATCH] Set page table of AP to BSP, to allow mapping of heap to be
 shared

---
 arch/x86_64/src/paging/mod.rs | 31 +++++++++++++++++++++++++++++++
 arch/x86_64/src/start.rs      | 14 ++++++++------
 2 files changed, 39 insertions(+), 6 deletions(-)

diff --git a/arch/x86_64/src/paging/mod.rs b/arch/x86_64/src/paging/mod.rs
index a616db3..d57c0d6 100644
--- a/arch/x86_64/src/paging/mod.rs
+++ b/arch/x86_64/src/paging/mod.rs
@@ -81,6 +81,37 @@ pub unsafe fn init(stack_start: usize, stack_end: usize) -> ActivePageTable {
     active_table
 }
 
+/// Initialize paging for AP
+pub unsafe fn init_ap(stack_start: usize, stack_end: usize, bsp_page_table: usize) -> ActivePageTable {
+    let mut active_table = ActivePageTable::new();
+
+    let mut temporary_page = TemporaryPage::new(Page::containing_address(VirtualAddress::new(0x80000000)));
+
+    let mut new_table = {
+        let frame = Frame::containing_address(PhysicalAddress::new(bsp_page_table));
+        InactivePageTable {
+            p4_frame: frame
+        }
+    };
+
+    active_table.with(&mut new_table, &mut temporary_page, |mapper| {
+        let mut remap = |start: usize, end: usize, flags: EntryFlags| {
+            let start_frame = Frame::containing_address(PhysicalAddress::new(start));
+            let end_frame = Frame::containing_address(PhysicalAddress::new(end - 1));
+            for frame in Frame::range_inclusive(start_frame, end_frame) {
+                mapper.identity_map(frame, flags);
+            }
+        };
+
+        // Remap stack writable, no execute
+        remap(stack_start, stack_end, PRESENT | WRITABLE | NO_EXECUTE);
+    });
+
+    active_table.switch(new_table);
+
+    active_table
+}
+
 pub struct ActivePageTable {
     mapper: Mapper,
 }
diff --git a/arch/x86_64/src/start.rs b/arch/x86_64/src/start.rs
index 6ab23a7..3526136 100644
--- a/arch/x86_64/src/start.rs
+++ b/arch/x86_64/src/start.rs
@@ -3,7 +3,8 @@
 /// It must create the IDT with the correct entries, those entries are
 /// defined in other files inside of the `arch` module
 
-use core::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, Ordering};
+use core::sync::atomic::{AtomicBool, ATOMIC_BOOL_INIT, AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+use x86::controlregs;
 
 use acpi;
 use allocator::{HEAP_START, HEAP_SIZE};
@@ -19,6 +20,7 @@ static BSS_TEST_ZERO: usize = 0;
 static BSS_TEST_NONZERO: usize = 0xFFFFFFFFFFFFFFFF;
 
 static BSP_READY: AtomicBool = ATOMIC_BOOL_INIT;
+static BSP_PAGE_TABLE: AtomicUsize = ATOMIC_USIZE_INIT;
 
 extern {
     /// Kernel main function
@@ -68,7 +70,9 @@ pub unsafe extern fn kstart() -> ! {
         // Initialize paging
         let mut active_table = paging::init(stack_start, stack_end);
 
-        // Read ACPI tables
+        BSP_PAGE_TABLE.store(controlregs::cr3() as usize, Ordering::SeqCst);
+
+        // Read ACPI tables, starts APs
         acpi::init(&mut active_table);
 
         // Map heap
@@ -95,10 +99,8 @@ pub unsafe extern fn kstart_ap(stack_start: usize, stack_end: usize) -> ! {
         idt::init_ap();
 
         // Initialize paging
-        //let mut active_table =
-        paging::init(stack_start, stack_end);
-
-        // TODO: Use heap from master, ensuring consistency
+        //let mut active_table = 
+        paging::init_ap(stack_start, stack_end, BSP_PAGE_TABLE.load(Ordering::SeqCst));
     }
 
     while ! BSP_READY.load(Ordering::SeqCst) {