From 7509a5d77ff2e3cd9616497c5376768a749170b6 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Tue, 14 Oct 2025 07:46:09 +0000
Subject: [PATCH] Add enhanced debugging for segment exceptions

Co-authored-by: ParrotXray <87219725+ParrotXray@users.noreply.github.com>
---
 kernel/src/arch/amd64/gdt.rs |  4 ++++
 kernel/src/arch/amd64/isr.rs | 18 ++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/kernel/src/arch/amd64/gdt.rs b/kernel/src/arch/amd64/gdt.rs
index a3d5f8d..08cbc3e 100644
--- a/kernel/src/arch/amd64/gdt.rs
+++ b/kernel/src/arch/amd64/gdt.rs
@@ -131,4 +131,8 @@ pub fn print_info() {
     log_info!("User Code:   {:#x} (ring 3)", selectors.user_code_selector.0);
     log_info!("User Data:   {:#x} (ring 3)", selectors.user_data_selector.0);
     log_info!("TSS:         {:#x}", selectors.tss_selector.0);
+    
+    // Verify that user segments have correct RPL bits
+    log_debug!("User Code RPL: {:?}", selectors.user_code_selector.rpl());
+    log_debug!("User Data RPL: {:?}", selectors.user_data_selector.rpl());
 }
\ No newline at end of file
diff --git a/kernel/src/arch/amd64/isr.rs b/kernel/src/arch/amd64/isr.rs
index c3d2737..ac3d46c 100644
--- a/kernel/src/arch/amd64/isr.rs
+++ b/kernel/src/arch/amd64/isr.rs
@@ -97,6 +97,15 @@ pub extern "x86-interrupt" fn invalid_tss_handler(
     kprintln!();
     log_fatal!("EXCEPTION: INVALID TSS (#TS)");
     log_fatal!("Error Code: {:#x}", error_code);
+    
+    // Decode the error code to provide more information
+    let selector_index = (error_code >> 3) & 0x1FFF;  // Bits 15-3
+    let ti = (error_code >> 2) & 0x1;                 // Bit 2: Table Indicator (0=GDT, 1=LDT)
+    let rpl = error_code & 0x3;                       // Bits 1-0: RPL
+    
+    log_fatal!("Segment Selector Index: {:#x} ({})", selector_index, selector_index);
+    log_fatal!("Table Indicator: {} ({})", ti, if ti == 0 { "GDT" } else { "LDT" });
+    log_fatal!("Requested Privilege Level: {}", rpl);
     log_fatal!("{:#?}", stack_frame);
     loop {
         cpu::cpu_halt();
@@ -111,6 +120,15 @@ pub extern "x86-interrupt" fn segment_not_present_handler(
     kprintln!();
     log_fatal!("EXCEPTION: SEGMENT NOT PRESENT (#NP)");
     log_fatal!("Error Code: {:#x}", error_code);
+    
+    // Decode the error code to provide more information
+    let selector_index = (error_code >> 3) & 0x1FFF;  // Bits 15-3
+    let ti = (error_code >> 2) & 0x1;                 // Bit 2: Table Indicator (0=GDT, 1=LDT)
+    let rpl = error_code & 0x3;                       // Bits 1-0: RPL
+    
+    log_fatal!("Segment Selector Index: {:#x} ({})", selector_index, selector_index);
+    log_fatal!("Table Indicator: {} ({})", ti, if ti == 0 { "GDT" } else { "LDT" });
+    log_fatal!("Requested Privilege Level: {}", rpl);
     log_fatal!("{:#?}", stack_frame);
     loop {
         cpu::cpu_halt();