process: Switch to kernel page table before (potentially) unmapping current page table on termination

Fixes hanging with high CPU usage on process termination.

2 files changed, 10 insertions, 1 deletions

diff --git a/src/lib/paging.zig b/src/lib/paging.zig
index 7dc25dd..a5beb13 100644
--- a/src/lib/paging.zig
+++ b/src/lib/paging.zig
@@ -37,6 +37,8 @@ pub const log2_page_size: u8 = @intCast(std.math.log2(page_size));
 
 pub var next_mmio_vaddr: usize = 0xff000000;
 
+pub var kmem: *Table = undefined;
+
 pub const AllocError = error{
     ZeroSize,
     OutOfMemory,
@@ -471,13 +473,16 @@ pub const Table = struct {
     }
 };
 
-pub fn init() void {
+pub fn init() !void {
     const num_pages = heapSize() / page_size;
     const pages: [*]Page = @ptrCast(heap_start);
 
     for (0..num_pages) |i| {
         pages[i].flags = Page.Flags.clear;
     }
+
+    kmem = @ptrCast(try zeroedAlloc(1));
+    try kmem.mapKernel();
 }
 
 // Allocate memory pages. Passing n <= 0 results in an error.
diff --git a/src/lib/process.zig b/src/lib/process.zig
index 3c902df..89ce369 100644
--- a/src/lib/process.zig
+++ b/src/lib/process.zig
@@ -164,6 +164,10 @@ pub const Info = struct {
     pub fn terminate(
         self: *Info,
     ) void {
+        instructions.satp.write(paging.kmem.satp(0));
+        // Probably not always needed. Let's not take the risk for now.
+        asm volatile ("sfence.vma");
+
         var node = list.first;
         while (node) |proc_node| : (node = proc_node.next) {
             if (self.shouldRemove(&proc_node.data)) {