Experiments with GDT

Makefile.toml

@@ -30,8 +30,6 @@ default_to_workspace = false
 LIMINEDIR = "/usr/share/limine"
 # Compile target
 TARGET = "x86_64-unknown-none"
-# Binaries included in the OS initramfs
-BINS = []
 
 [env.development]
 PROFILE = "dev"
@@ -61,7 +59,7 @@ alias = "run"
 
 
 [tasks.clean_all]
-run_task = { name = ["clean_kernel", "clean_initramfs", "clean_iso"] }
+run_task = { name = ["clean_kernel", "clean_iso"] }
 
 [tasks.clean_kernel]
 command = "cargo"
@@ -74,10 +72,6 @@ script = "rustup install nightly; rustup target add ${TARGET}"
 command = "rm"
 args = ["-rf", "build/iso", "build/gila.iso"]
 
-[tasks.clean_initramfs]
-command = "rm"
-args = ["-rf", "build/initramfs", "build/initramfs.tar.lzma"]
-
 [tasks.lib]
 condition = { files_modified = { input = ["libgila/src/**/*.rs"], output = ["${ARTIFACTDIR}/libgila.rlib"] }, fail_message = "(inputs unchanged)" }
 dependencies = []
@@ -94,34 +88,6 @@ dependencies = ["lib"]
 command = "cargo"
 args = ["build", "--profile", "${PROFILE}", "-p", "kernel"]
 
-[tasks.bins]
-dependencies = []
-
-
-
-
-
-[tasks.initramfs]
-condition = { files_modified = { input = [
-    # This will not depend on *every* binary we build.
-    # If we mount a disk later in boot we can store other binaries there.
-    "configs/server_config.toml"
-], output = ["build/${ARCH}/initramfs.tar.lzma"] }, fail_message = "(inputs unchanged)" }
-dependencies = ["bins"]
-script = '''
-    mkdir -p build/initramfs/system/bin
-    mkdir -p build/initramfs/system/cfg
-    mkdir -p build/${ARCH}
-
-    for bin in $(echo ${BINS} | tr ";" " ")
-    do
-        cp ${ARTIFACTDIR}/$bin build/initramfs/system/bin/
-    done
-    cp configs/server_config.toml build/initramfs/system/cfg/
-
-    tar -c --lzma -f build/${ARCH}/initramfs.tar.lzma build/initramfs
-'''
-
 [tasks.iso]
 condition = { files_modified = { input = [
     "${ARTIFACTDIR}/kernel", 
@@ -131,7 +97,7 @@ condition = { files_modified = { input = [
     "${LIMINEDIR}/limine-uefi-cd.bin",
     "${LIMINEDIR}/${LIMINEBIN}"
 ], output = ["build/gila.iso"] }, fail_message = "(inputs unchanged)" }
-dependencies = ["kernel", "initramfs"]
+dependencies = ["kernel"]
 script = '''
     mkdir -p build/iso/boot/limine
 	mkdir -p build/iso/EFI/BOOT
@@ -142,14 +108,9 @@ script = '''
 	cp -f ${LIMINEDIR}/limine-bios-cd.bin build/iso/boot/limine/
 	cp -f ${LIMINEDIR}/limine-uefi-cd.bin build/iso/boot/limine/
 	cp -f ${LIMINEDIR}/${LIMINEBIN} build/iso/EFI/BOOT
-    cp -f build/${ARCH}/initramfs.tar.lzma build/iso/boot/${ARCH}
 
 	cp -f ${ARTIFACTDIR}/kernel build/iso/boot/${ARCH}/gila
 
-	mkdir -p build/iso/system/bin
-	mkdir -p build/iso/system/tmp
-	mkdir -p build/iso/system/cfg
-
 	xorriso -as mkisofs \
     -b boot/limine/limine-bios-cd.bin \
     -no-emul-boot \

configs/init.toml

@@ -0,0 +1,6 @@
+[deployment]
+libgila_version = "0.1.0"
+arch = "x86_64"
+# Optional
+name = "example"
+version = "0.1.0"

configs/server_config.toml

@@ -1,13 +0,0 @@
-# The configuration file detailing which system servers
-# are responsible for what responsibilities.
-
-# This configuration file details several tables. Each table
-# is a category of server the OS will launch to provide
-# userspace functionality. Each key in the table is a specific
-# functionality.
-
-[filesystems]
-
-[devices]
-
-[services]

docs/API.md

@@ -0,0 +1,28 @@
+# Application Programming Interface
+
+## Overview
+
+The Gila microkernel has a very limited API surface, but several components
+developed alongside it expose additional functionality- such as `libgila` and
+Userboot, which are treated as extensions of the kernel.
+
+## The libgila Library
+
+The `libgila` library is shared between the kernel and any binaries built for
+it, serving to abstract the syscall API and any structures or protocols that
+pass the kernel-mode boundary. It provides the official kernel API, and its
+version number is incremented independent of the kernel's.
+
+## Userboot
+
+Userboot is an early-boot program which is launched as the first unprivileged
+process by Gila. The kernel will pass several pieces of data to it, such as the
+addresses of device tree blobs, framebuffers, and ACPI tables. These addresses
+will not necessarily be mapped to memory. What the kernel *will* map is the
+page range containing the initramfs, which Userboot is responsible for
+decompressing and parsing. If the initramfs's structure & manifest file do not
+match the specification denoted here, Userboot will fail to complete the boot
+process.
+
+## Initramfs Structure
+

kernel/src/arch/x86_64/gdt.rs

@@ -42,7 +42,8 @@ pub fn read_gdt() -> GlobalDescriptorTable {
     // x86 gdtr: Lower 2 8-bit bytes (lower 16 bits) is the size of the GDT,
     // in 8-bit bytes, minus one.
     // Bits 16 through 79 are the virtual address of the GDT.
-    let (limit, addr) = (addr.bits(0..=15) as usize + 1, addr.bits(16..=79) as u64);
+    let limit = addr.bits(0..=15) as usize + 1;
-    let gdt_raw: &[u64] = unsafe { core::slice::from_raw_parts(addr as *const u64, limit / 8) };
+    let base = addr.bits(16..=79) as u64;
+    let gdt_raw: &[u64] = unsafe { core::slice::from_raw_parts(base as *const u64, (limit / 8) - 1) };
     GlobalDescriptorTable::from_raw_entries(gdt_raw)
 }

kernel/src/main.rs

@@ -16,6 +16,8 @@ mod panic;
 mod process;
 mod util;
 
+use core::{arch::asm, ptr::addr_of};
+
 use arch::x86_64::interrupts::IDT;
 use arch::x86_64::serial::SerialPort;
 use boot::{BASE_REVISION, params, *};
@@ -28,7 +30,10 @@ use lazy_static::lazy_static;
 use limine::firmware_type::FirmwareType;
 use spin::mutex::Mutex;
 
-use crate::{arch::x86_64::cpuid::{CPUID, virt_supported}, memory::HHDM_RESPONSE};
+use crate::{
+    arch::x86_64::{cpuid::{CPUID, virt_supported}, gdt::GdtEntryRead},
+    memory::HHDM_RESPONSE,
+};
 
 lazy_static! {
     pub static ref SERIAL_3F8: Mutex<SerialPort> = Mutex::new(
@@ -153,9 +158,18 @@ unsafe extern "C" fn main() -> ! {
 
     let l4_start = x86_64::registers::control::Cr3::read().0.start_address();
     log_info!("Physical address of current L4 table: 0x{:x}", l4_start);
-    log_info!("Virtual address of current L4 table: 0x{:x}", l4_start.as_u64() + HHDM_RESPONSE.offset());
+    log_info!(
+        "Virtual address of current L4 table: 0x{:x}",
+        l4_start.as_u64() + HHDM_RESPONSE.offset()
+    );
 
     //iter_table(4, &PML4);
 
+    let gdt = crate::arch::x86_64::gdt::read_gdt();
+    log_info!("GDT length: {}", gdt.limit() + 1);
+    for entry in gdt.entries() {
+        log_info!("GDT entry: Flags 0b{:b}, Access 0b{:b}", entry.flags(), entry.access());
+    }
+
     panic!("Finished boot, but cannot start init because processes not implemented!");
 }