v0.8.3: basic fork impl

Author: GZTimeWalker

Cargo.lock

@@ -3,26 +3,43 @@
 
 extern crate alloc;
 extern crate lib;
-
 use lib::*;
 
+static mut M: u64 = 0xdeadbeef;
+
 fn main() {
-    let mut c = 23;
+    let mut c = 32;
+
+    // do not alloc heap before `fork`
+    // which may cause unexpected behavior since we won't copy the heap in `fork`
     let ret = sys_fork();
 
     if ret == 0 {
-        // println!("I am the child process");
-        // println!("Exiting...");
+        println!("I am the child process");
+        unsafe {
+            println!("child read value of M: {:#x}", &M);
+        }
+        unsafe {
+            M = 0x2333;
+            println!("child changed the value of M: {:#x}", &M);
+        }
         c += 32;
     } else {
-        // println!("I am the parent process");
-        // println!("Waiting for child to exit...");
-        // let ret = sys_wait_pid(ret);
-        // println!("Child exited with status {}", ret);
-        c += 24;
-    }
-    unsafe {
-        core::arch::asm!("hlt");
+        println!("I am the parent process");
+
+        sys_stat();
+
+        println!("Waiting for child to exit...");
+
+        let ret = sys_wait_pid(ret);
+
+        println!("Child exited with status {}", ret);
+
+        unsafe {
+            println!("parent read value of M: {:#x}", &M);
+        }
+
+        c += 1024;
     }
     sys_exit(c);
 }

pkg/app/fork/src/main.rs

@@ -13,7 +13,8 @@ use alloc::string::String;
 extern crate lib;
 
 fn main() {
-    sys_spawn("/APP/FORK");
+    services::exec("FORK", "/APP/");
+
     let mut root_dir = String::from("/APP/");
     println!("<<< Welcome to GGOS shell >>>");
     loop {

pkg/app/sh/src/main.rs

@@ -116,8 +116,6 @@ pub fn exec(path: &str, root_dir: &str) {
     if pid == 0 {
         errln!("failed to spawn process: {}", path);
         return;
-    } else {
-        println!("[+] spawned process: {}#{}", path, pid);
     }
 
     let ret = sys_wait_pid(pid);

pkg/app/sh/src/services.rs

@@ -65,7 +65,7 @@ pub fn map_stack(
     page_table: &mut impl Mapper<Size4KiB>,
     frame_allocator: &mut impl FrameAllocator<Size4KiB>,
 ) -> Result<(), MapToError<Size4KiB>> {
-    trace!("mapping stack at {:#x}", addr);
+    trace!("Mapping stack at {:#x}", addr);
     // create a stack
     let stack_start = Page::containing_address(VirtAddr::new(addr));
     let stack_end = stack_start + pages;
@@ -83,6 +83,8 @@ pub fn map_stack(
         }
     }
 
+    trace!("Stack hint: {:#x} -> {:#x}", addr, page_table.translate_page(stack_start).unwrap().start_address());
+
     Ok(())
 }
 
@@ -94,9 +96,12 @@ pub fn unmap_stack(
     frame_deallocator: &mut impl FrameDeallocator<Size4KiB>,
     do_dealloc: bool,
 ) -> Result<(), UnmapError> {
-    trace!("unmapping stack at {:#x}", addr);
+    trace!("Unmapping stack at {:#x}", addr);
 
     let stack_start = Page::containing_address(VirtAddr::new(addr));
+
+    trace!("Stack hint: {:#x} -> {:#x}", addr, page_table.translate_page(stack_start).unwrap().start_address());
+
     let stack_end = stack_start + pages;
 
     for page in Page::range(stack_start, stack_end) {
@@ -135,13 +140,16 @@ fn map_segment(
 
     let flags = segment.flags();
     let mut page_table_flags = PageTableFlags::PRESENT;
+
     if !flags.is_execute() {
-        page_table_flags |= PageTableFlags::NO_EXECUTE
-    };
+        page_table_flags |= PageTableFlags::NO_EXECUTE;
+    }
+
     if flags.is_write() {
-        page_table_flags |= PageTableFlags::WRITABLE
-    };
+        page_table_flags |= PageTableFlags::WRITABLE;
+    }
 
+    trace!("Segment page table flag: {:?}", page_table_flags);
     for frame in PhysFrame::range_inclusive(start_frame, end_frame) {
         let offset = frame - start_frame;
         let page = start_page + offset;

pkg/elf/src/lib.rs

@@ -1,6 +1,6 @@
 [package]
 name = "ggos_kernel"
-version = "0.8.0"
+version = "0.8.3"
 edition = "2021"
 authors = ["GZTime <Time.GZ@outlook.com>"]
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

pkg/kernel/Cargo.toml

@@ -1,6 +1,7 @@
 use super::*;
 use crate::utils::Registers;
 use x86_64::structures::idt::{InterruptDescriptorTable, InterruptStackFrame, PageFaultErrorCode};
+use x86_64::registers::control::Cr2;
 
 pub unsafe fn reg_idt(idt: &mut InterruptDescriptorTable) {
     idt.divide_error.set_handler_fn(divide_error_handler);
@@ -24,8 +25,10 @@ pub unsafe fn reg_idt(idt: &mut InterruptDescriptorTable) {
         .set_handler_fn(stack_segment_fault_handler);
     idt.general_protection_fault
         .set_handler_fn(general_protection_fault_handler);
+
     idt.page_fault.set_handler_fn(page_fault_handler)
-        .set_stack_index(crate::gdt::SYSCALL_IST_INDEX);
+        .set_stack_index(crate::gdt::PAGE_FAULT_IST_INDEX);
+
     idt.alignment_check.set_handler_fn(alignment_check_handler);
     idt.machine_check.set_handler_fn(machine_check_handler);
     idt.simd_floating_point
@@ -157,13 +160,11 @@ pub extern "C" fn syscall(mut regs: Registers, mut sf: InterruptStackFrame) {
 as_handler!(syscall);
 
 pub extern "x86-interrupt" fn page_fault_handler(
-    mut stack_frame: InterruptStackFrame,
+    stack_frame: InterruptStackFrame,
     err_code: PageFaultErrorCode,
 ) {
-    if let Err(_) = crate::process::try_resolve_page_fault(err_code, &mut stack_frame) {
-        panic!(
-            "EXCEPTION: PAGE FAULT, ERROR_CODE: {:?}\n\n{:#?}",
-            err_code, stack_frame
-        );
-    }
+    panic!(
+        "EXCEPTION: PAGE FAULT, ERROR_CODE: {:?}\n\nTrying to access: {:#x}\n{:#?}",
+        err_code, Cr2::read(), stack_frame
+    );
 }

pkg/kernel/src/interrupt/handlers.rs

@@ -5,6 +5,7 @@ use x86_64::VirtAddr;
 
 pub const DOUBLE_FAULT_IST_INDEX: u16 = 0;
 pub const SYSCALL_IST_INDEX: u16 = 1;
+pub const PAGE_FAULT_IST_INDEX: u16 = 2;
 pub const CONTEXT_SWITCH_IST_INDEX: u16 = 0;
 
 lazy_static! {
@@ -23,7 +24,15 @@ lazy_static! {
             static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];
             let stack_start = VirtAddr::from_ptr(unsafe { &STACK });
             let stack_end = stack_start + STACK_SIZE;
-            info!("Syscall IST:      0x{:016x}-0x{:016x}", stack_start.as_u64(), stack_end.as_u64());
+            info!("Syscall IST     : 0x{:016x}-0x{:016x}", stack_start.as_u64(), stack_end.as_u64());
+            stack_end
+        };
+        tss.interrupt_stack_table[PAGE_FAULT_IST_INDEX as usize] = {
+            const STACK_SIZE: usize = 0x2000;
+            static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];
+            let stack_start = VirtAddr::from_ptr(unsafe { &STACK });
+            let stack_end = stack_start + STACK_SIZE;
+            info!("Page Fault IST  : 0x{:016x}-0x{:016x}", stack_start.as_u64(), stack_end.as_u64());
             stack_end
         };
         tss

pkg/kernel/src/memory/gdt.rs

@@ -157,7 +157,7 @@ impl ProcessManager {
         p.pause();
         p.init_stack_frame(
             VirtAddr::new_truncate(elf.header.pt2.entry_point()),
-            VirtAddr::new_truncate(STACK_TOP),
+            VirtAddr::new_truncate(STACK_BOT + STACK_SIZE),
         );
         p.init_elf(elf);
         // info!("Spawn process: {}#{}", p.name(), p.pid());

pkg/kernel/src/process/manager.rs

@@ -22,8 +22,9 @@ use x86_64::structures::idt::PageFaultErrorCode;
 use self::manager::init_PROCESS_MANAGER;
 
 const STACK_BOT: u64 = 0x0000_2000_0000_0000;
-const STACK_PAGES: u64 = 512;
-const STACK_TOP: u64 = STACK_BOT + STACK_PAGES * 0x1000;
+const STACK_PAGES: u64 = 0x200;
+const STACK_SIZE: u64 = STACK_PAGES * crate::memory::PAGE_SIZE;
+const STACK_START_MASK: u64 = !(STACK_SIZE - 1);
 
 #[derive(Debug, Copy, Clone, Eq, PartialEq)]
 pub enum ProgramStatus {
@@ -34,7 +35,7 @@ pub enum ProgramStatus {
     Dead,
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
 pub struct ProcessId(pub u16);
 
 impl ProcessId {
@@ -50,6 +51,12 @@ impl core::fmt::Display for ProcessId {
     }
 }
 
+impl core::fmt::Debug for ProcessId {
+    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
 impl From<ProcessId> for u16 {
     fn from(pid: ProcessId) -> Self {
         pid.0
@@ -130,13 +137,13 @@ pub fn current_pid() -> ProcessId {
     })
 }
 
-pub fn try_resolve_page_fault(err_code: PageFaultErrorCode, sf: &mut InterruptStackFrame) -> Result<(),()> {
+pub fn try_resolve_page_fault(_err_code: PageFaultErrorCode, _sf: &mut InterruptStackFrame) -> Result<(),()> {
     let addr = Cr2::read();
     debug!("Trying to access address: {:?}", addr);
 
     x86_64::instructions::interrupts::without_interrupts(|| {
         let manager = get_process_manager_for_sure();
-        debug!("Current process: {:?}", manager.current());
+        debug!("Current process: {:#?}", manager.current());
     });
 
     Err(())