process: Disable interrupts while switching to U-mode

2 files changed, 10 insertions, 3 deletions

diff --git a/src/lib/interrupts.zig b/src/lib/interrupts.zig
index f9a9ca1..ebb6e9a 100644
--- a/src/lib/interrupts.zig
+++ b/src/lib/interrupts.zig
@@ -99,6 +99,10 @@ export fn handleTrap(epc: usize, tval: usize, cause_bits: usize, frame: *trap.Fr
         switch (@as(AsyncCause, @enumFromInt(cause.num))) {
             .supervisor_software => w.print("Hart {d}: Software interrupt\r\n", .{frame.hart_id}) catch unreachable,
             .supervisor_timer => {
+                defer time.interruptInMillis(process.schedule_interval_millis) catch |err| {
+                    std.debug.panic("Hart {d}: Unable to reset interrupt timer: {any}", .{ frame.hart_id, err });
+                };
+
                 if (status.previous_privilege == .user) {
                     // Trapped from U-mode, update pc for next time slice.
                     //
diff --git a/src/lib/process.zig b/src/lib/process.zig
index e07c6a4..c227fdb 100644
--- a/src/lib/process.zig
+++ b/src/lib/process.zig
@@ -93,12 +93,15 @@ pub fn next() ?*Info {
 pub fn switchTo(proc: *Info) noreturn {
     proc.state = .active;
 
-    instructions.sscratch.write(@intFromPtr(&proc.trap_frame));
-
     var sstatus = instructions.sstatus.read();
     sstatus.previous_privilege = .user;
+    sstatus.user_interrupt_enable = 0;
+    sstatus.supervisor_interrupt_enable = 0;
+    sstatus.user_prior_interrupt_enable = 1;
+    sstatus.supervisor_prior_interrupt_enable = 1;
     instructions.sstatus.write(sstatus);
 
+    instructions.sscratch.write(@intFromPtr(&proc.trap_frame));
     instructions.sepc.write(proc.pc);
     instructions.satp.write(proc.satp());
 
@@ -163,5 +166,5 @@ pub fn demo(allocator: std.mem.Allocator) !noreturn {
     list.prepend(proc_node);
 
     try time.interruptInMillis(schedule_interval_millis);
-    try switchTo(&proc_node.data);
+    switchTo(&proc_node.data);
 }