From ae70cb7e4febc45ebed829b37763390bb7a1b2b1 Mon Sep 17 00:00:00 2001
From: Amaan Cheval <amaan.cheval@gmail.com>
Date: Thu, 20 Sep 2018 00:30:32 +0530
Subject: [PATCH] cpu: Minor refactor in call_interrupt_vector

---
 src/browser/starter.js |  1 +
 src/rust/cpu2/cpu.rs   | 16 +++++++++++-----
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/src/browser/starter.js b/src/browser/starter.js
index 27e4e1f2..23b44442 100644
--- a/src/browser/starter.js
+++ b/src/browser/starter.js
@@ -257,6 +257,7 @@ function V86Starter(options)
         "abs": Math.abs,
 
         "do_task_switch": (selector, error_code) => cpu.do_task_switch(selector, error_code),
+        // XXX: Port to Rust
         "get_tss_stack_addr": (dpl) => cpu.get_tss_stack_addr(dpl),
         "switch_cs_real_mode": (selector) => cpu.switch_cs_real_mode(selector),
     };
diff --git a/src/rust/cpu2/cpu.rs b/src/rust/cpu2/cpu.rs
index 0c297529..138ab556 100644
--- a/src/rust/cpu2/cpu.rs
+++ b/src/rust/cpu2/cpu.rs
@@ -438,14 +438,17 @@ pub unsafe fn call_interrupt_vector(
 
         if !is_valid_type || !reserved_zeroes_are_valid {
             // invalid gate_type
-            dbg_trace();
-            dbg_log!("invalid gate_type: 0b{:b}", gate_type);
+            dbg_log!(
+                "gate type invalid or reserved 0s violated. gate_type=0b{:b}",
+                gate_type
+            );
             dbg_log!(
                 "addr={:x} offset={:x} selector={:x}",
                 descriptor_address,
                 offset,
                 selector
             );
+            dbg_trace();
             panic!("Unimplemented: #GP handler");
         }
 
@@ -524,14 +527,14 @@ pub unsafe fn call_interrupt_vector(
 
             let error_code_space = if has_error_code == true { 1 } else { 0 };
             let vm86_space = if (old_flags & FLAG_VM) == FLAG_VM {
-                1
+                4
             }
             else {
                 0
             };
             let bytes_per_arg = if is_16 { 2 } else { 4 };
 
-            let stack_space = bytes_per_arg * (5 + error_code_space + 4 * vm86_space);
+            let stack_space = bytes_per_arg * (5 + error_code_space + vm86_space);
             let new_stack_pointer = ss_segment_descriptor.base() + if ss_segment_descriptor.is_32()
             {
                 new_esp - stack_space
@@ -545,6 +548,7 @@ pub unsafe fn call_interrupt_vector(
                 ss_segment_descriptor.base() + new_esp - 1
             ));
 
+            // no exceptions below
             *cpl = cs_segment_descriptor.dpl();
             cpl_changed();
 
@@ -553,11 +557,13 @@ pub unsafe fn call_interrupt_vector(
             *flags &= !FLAG_VM & !FLAG_RF;
 
             if !switch_seg(SS, new_ss) {
+                // XXX
                 dbg_assert!(false);
-            } // XXX
+            }
             set_stack_reg(new_esp);
 
             // XXX: #SS if stack would cross stack limit
+
             if old_flags & FLAG_VM != 0 {
                 if is_16 {
                     dbg_assert!(false);