fixing GPFs

src/kernel/arch/x86_64/gdt.rs

@@ -54,7 +54,6 @@ pub struct Selectors {
     pub sel_kernel_stack: SegmentSelector,
     pub sel_user_code: SegmentSelector,
     pub sel_user_stack: SegmentSelector,
-    #[allow(unused)]
     pub sel_tss: SegmentSelector,
     pub gdt: GlobalDescriptorTable<48>,
 }
@@ -79,7 +78,7 @@ lazy_static! {
         // DO NOT REORDER
         let sel_tss = gdt.append(
             Descriptor::tss_segment(&TSS).set_flags(DescriptorFlags::from_bits_retain(0b1010))
-            //.set_access(0b10001011), // This would set the TSS to Busy, but it causes a GPF.
+                .set_access(0b10001011), // This would set the TSS to Busy, but it causes a GPF.
         );
         Selectors {
             sel_kernel_code: sel_k_cs,

src/kernel/arch/x86_64/interrupts.rs

@@ -23,9 +23,9 @@ lazy_static! {
         // code. The x86_interrupt ABI is always breaking, and this
         // approach will fall apart once multiarch support is re-added.
         unsafe {
-            idt.double_fault.set_handler_fn(double_fault).set_code_selector(SELECTORS.sel_kernel_code).set_privilege_level(x86_64::PrivilegeLevel::Ring0);
+            idt.double_fault.set_handler_fn(double_fault).set_code_selector(SELECTORS.sel_kernel_code);
-            idt.page_fault.set_handler_fn(page_fault).set_code_selector(SELECTORS.sel_kernel_code).set_privilege_level(x86_64::PrivilegeLevel::Ring0);
+            idt.page_fault.set_handler_fn(page_fault).set_code_selector(SELECTORS.sel_kernel_code);
-            idt.general_protection_fault.set_handler_fn(gen_prot_fault).set_code_selector(SELECTORS.sel_kernel_code).set_privilege_level(x86_64::PrivilegeLevel::Ring0);
+            idt.general_protection_fault.set_handler_fn(gen_prot_fault).set_code_selector(SELECTORS.sel_kernel_code);
         }
         idt
     };
@@ -35,6 +35,7 @@ lazy_static! {
 #[allow(dead_code)]
 extern "x86-interrupt" fn double_fault(info: InterruptStackFrame, _: u64) -> ! {
     crate::interrupt::double_fault(format!("{info:#?}"));
+    unsafe { info.iretq() }
 }
 
 #[allow(dead_code)]
@@ -68,11 +69,13 @@ extern "x86-interrupt" fn page_fault(info: InterruptStackFrame, errcode: PageFau
 }
 
 #[allow(dead_code)]
-extern "x86-interrupt" fn gen_prot_fault(info: InterruptStackFrame, _: u64) {
+extern "x86-interrupt" fn gen_prot_fault(info: InterruptStackFrame, error: u64) {
     crate::interrupt::gen_prot_fault(format!(
-        "RIP 0x{:x}, CS {} ({:?})",
+        "RIP 0x{:x}, CS {} ({:?}), error: 0x{:x}",
         info.instruction_pointer,
         info.code_segment.index(),
-        info.code_segment.rpl()
+        info.code_segment.rpl(),
+        error
     ));
+    unsafe { info.iretq() }
 }

src/kernel/arch/x86_64/startup.rs

@@ -3,7 +3,10 @@ use x86_64::{VirtAddr, registers::rflags::RFlags, structures::idt::InterruptStac
 use crate::{
     arch::{
         asm::ltr,
-        x86_64::{gdt::SELECTORS, interrupts::IDT},
+        x86_64::{
+            gdt::{SELECTORS, dump_gdt},
+            interrupts::IDT,
+        },
     },
     log::{LOGGER, LogLevel},
     log_info,
@@ -24,6 +27,7 @@ pub fn init() -> Result<(), ()> {
         SELECTORS.sel_kernel_stack,
     )
     .expect("Segment order in GDT is bad");
+    dump_gdt();
     ltr(SELECTORS.sel_tss.index());
     Ok(())
 }

src/kernel/interrupt/mod.rs

@@ -4,8 +4,8 @@
 use crate::log::*;
 use crate::{format, log_error, memory::alloc::string::String};
 
-pub fn double_fault(info: String) -> ! {
+pub fn double_fault(info: String) {
-    panic!("Double fault: {}", info);
+    log_error!("Double fault: {}", info);
 }
 
 pub fn page_fault_fatal(addr: usize, info: String) -> ! {

src/kernel/main.rs

@@ -177,6 +177,7 @@ unsafe extern "C" fn main() -> ! {
     {
         let ub = modules_list.modules()[0];
         log_info!("Found userboot: {} {}", ub.path(), ub.cmdline());
+        // TODO: remap userboot as user pages
 
         let start_addr = VirtAddr::from_ptr(ub.data() as *const [u8]);
         arch::startup::jump_to_usermode(VirtAddr::new(0xfffffff800000000), start_addr)