vasilito/RedBear-OS
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Statically allocate PCR for the BSP

Browse Source
This commit is contained in:
bjorn3
2025-09-15 20:53:51 +02:00
parent 4884d749af
commit 019564ee0e
2 changed files with 69 additions and 37 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/arch/x86_shared/gdt.rs
+67 -29
View File
@@ -1,5 +1,7 @@
//! Global descriptor table
use core::ptr;
#[cfg(target_arch = "x86")]
use x86::bits32::task::TaskStateSegment;
#[cfg(target_arch = "x86_64")]
@@ -66,6 +68,8 @@ const SEGMENT_FLAGS: u8 = GDT_F_PAGE_SIZE | GDT_F_PROTECTED_MODE;
#[cfg(target_arch = "x86_64")]
const SEGMENT_FLAGS: u8 = GDT_F_LONG_MODE;
// Make sure that the entries we load as segments have the dirty flag set already!
// INIT_GDT is read-only, but loading a segment would set the dirty flag if it isn't already.
static INIT_GDT: [GdtEntry; 3] = [
// Null
GdtEntry::new(0, 0, 0, 0),
@@ -73,14 +77,19 @@ static INIT_GDT: [GdtEntry; 3] = [
GdtEntry::new(
0,
SEGMENT_LIMIT,
GDT_A_PRESENT | GDT_A_RING_0 | GDT_A_SYSTEM | GDT_A_EXECUTABLE | GDT_A_PRIVILEGE,
GDT_A_PRESENT
| GDT_A_DIRTY
| GDT_A_RING_0
| GDT_A_SYSTEM
| GDT_A_EXECUTABLE
| GDT_A_PRIVILEGE,
SEGMENT_FLAGS,
),
// Kernel data
GdtEntry::new(
0,
SEGMENT_LIMIT,
GDT_A_PRESENT | GDT_A_RING_0 | GDT_A_SYSTEM | GDT_A_PRIVILEGE,
GDT_A_PRESENT | GDT_A_DIRTY | GDT_A_RING_0 | GDT_A_SYSTEM | GDT_A_PRIVILEGE,
SEGMENT_FLAGS,
),
];
@@ -168,7 +177,7 @@ struct Align([u64; 2]);
pub struct ProcessorControlRegion {
// TODO: When both KASLR and KPTI are implemented, the PCR may need to be split into two pages,
// such that "secret" kernel addresses are only stored in the protected half.
pub self_ref: usize,
pub self_ref: *mut ProcessorControlRegion,
pub user_rsp_tmp: usize,
// The GDT *must* be stored in the PCR! The paranoid interrupt handler, lacking a reliable way
@@ -194,6 +203,21 @@ const _: () = {
}
};
impl ProcessorControlRegion {
const fn new_partial_init(cpu_id: LogicalCpuId) -> Self {
Self {
self_ref: ptr::null_mut(),
user_rsp_tmp: 0,
gdt: BASE_GDT,
percpu: PercpuBlock::init(cpu_id),
_rsvd: Align([0; 2]),
tss: TaskStateSegment::new(),
_iobitmap: [0; IOBITMAP_SIZE as usize],
_all_ones: 0xFF,
}
}
}
pub unsafe fn pcr() -> *mut ProcessorControlRegion {
unsafe {
// Primitive benchmarking of RDFSBASE and RDGSBASE in userspace, appears to indicate that
@@ -301,20 +325,10 @@ unsafe fn load_segments() {
}
}
/// Initialize GDT and configure percpu.
#[cold]
pub unsafe fn init_paging(stack_offset: usize, cpu_id: LogicalCpuId) {
let alloc_order = size_of::<ProcessorControlRegion>()
.div_ceil(PAGE_SIZE)
.next_power_of_two()
.trailing_zeros();
unsafe fn init_and_install_pcr(pcr_ptr: *mut ProcessorControlRegion, stack_end: usize) {
let pcr = unsafe { &mut *pcr_ptr };
let pcr_frame = crate::memory::allocate_p2frame(alloc_order).expect("failed to allocate PCR");
let pcr = unsafe {
&mut *(RmmA::phys_to_virt(pcr_frame.base()).data() as *mut ProcessorControlRegion)
};
pcr.self_ref = pcr as *const _ as usize;
pcr.self_ref = pcr_ptr;
// Setup the GDT.
pcr.gdt = BASE_GDT;
@@ -327,8 +341,7 @@ pub unsafe fn init_paging(stack_offset: usize, cpu_id: LogicalCpuId) {
};
#[cfg(target_arch = "x86")]
unsafe {
pcr._all_ones = 0xFF;
{
pcr.tss.iobp_offset = 0xFFFF;
let tss = &pcr.tss as *const _ as usize as u32;
@@ -337,9 +350,8 @@ pub unsafe fn init_paging(stack_offset: usize, cpu_id: LogicalCpuId) {
}
#[cfg(target_arch = "x86_64")]
unsafe {
{
pcr.tss.iomap_base = 0xFFFF;
pcr._all_ones = 0xFF;
let tss = &mut pcr.tss as *mut TaskStateSegment as usize as u64;
let tss_lo = (tss & 0xFFFF_FFFF) as u32;
@@ -348,9 +360,11 @@ pub unsafe fn init_paging(stack_offset: usize, cpu_id: LogicalCpuId) {
pcr.gdt[GDT_TSS].set_offset(tss_lo);
pcr.gdt[GDT_TSS].set_limit(size_of::<TaskStateSegment>() as u32 + IOBITMAP_SIZE);
(&mut pcr.gdt[GDT_TSS_HIGH] as *mut GdtEntry)
.cast::<u32>()
.write(tss_hi);
unsafe {
(&mut pcr.gdt[GDT_TSS_HIGH] as *mut GdtEntry)
.cast::<u32>()
.write(tss_hi);
}
}
// Load the new GDT, which is correctly located in thread local storage.
@@ -388,14 +402,38 @@ pub unsafe fn init_paging(stack_offset: usize, cpu_id: LogicalCpuId) {
// Set the stack pointer to use when coming back from userspace.
unsafe {
set_tss_stack(pcr, stack_offset);
set_tss_stack(pcr, stack_end);
}
// Load the task register
unsafe { task::load_tr(SegmentSelector::new(GDT_TSS as u16, Ring::Ring0)) };
pcr.percpu = PercpuBlock::init(cpu_id);
unsafe { crate::percpu::init_tlb_shootdown(cpu_id, &mut pcr.percpu) };
unsafe { crate::percpu::init_tlb_shootdown(pcr.percpu.cpu_id, &mut pcr.percpu) };
}
/// Initialize GDT and configure percpu for the BSP.
#[cold]
pub unsafe fn init_bsp(stack_end: usize) {
static mut BSP_PCR: ProcessorControlRegion =
ProcessorControlRegion::new_partial_init(LogicalCpuId::BSP);
unsafe { init_and_install_pcr(ptr::addr_of_mut!(BSP_PCR), stack_end) };
}
/// Initialize GDT and configure percpu.
#[cold]
pub unsafe fn init_paging(stack_end: usize, cpu_id: LogicalCpuId) {
let alloc_order = size_of::<ProcessorControlRegion>()
.div_ceil(PAGE_SIZE)
.next_power_of_two()
.trailing_zeros();
let pcr_frame = crate::memory::allocate_p2frame(alloc_order).expect("failed to allocate PCR");
let pcr_ptr =
unsafe { RmmA::phys_to_virt(pcr_frame.base()).data() as *mut ProcessorControlRegion };
unsafe { core::ptr::write(pcr_ptr, ProcessorControlRegion::new_partial_init(cpu_id)) };
unsafe { init_and_install_pcr(pcr_ptr, stack_end) };
}
#[derive(Copy, Clone, Debug)]
@@ -422,17 +460,17 @@ impl GdtEntry {
}
#[cfg(target_arch = "x86")]
pub fn offset(&self) -> u32 {
pub const fn offset(&self) -> u32 {
(self.offsetl as u32) | ((self.offsetm as u32) << 16) | ((self.offseth as u32) << 24)
}
pub fn set_offset(&mut self, offset: u32) {
pub const fn set_offset(&mut self, offset: u32) {
self.offsetl = offset as u16;
self.offsetm = (offset >> 16) as u8;
self.offseth = (offset >> 24) as u8;
}
pub fn set_limit(&mut self, limit: u32) {
pub const fn set_limit(&mut self, limit: u32) {
self.limitl = limit as u16;
self.flags_limith = self.flags_limith & 0xF0 | ((limit >> 16) as u8) & 0x0F;
}
src/arch/x86_shared/start.rs
+2 -8
View File
@@ -116,8 +116,8 @@ pub unsafe extern "C" fn kstart(args_ptr: *const KernelArgs) -> ! {
{ args.bootstrap_base } + { args.bootstrap_size }
);
// Set up GDT before paging
gdt::init();
// Set up GDT
gdt::init_bsp(args.stack_base as usize + args.stack_size as usize);
// Set up IDT before paging
idt::init();
@@ -157,12 +157,6 @@ pub unsafe extern "C" fn kstart(args_ptr: *const KernelArgs) -> ! {
// Initialize paging
paging::init();
// Set up GDT after paging with TLS
gdt::init_paging(
args.stack_base as usize + args.stack_size as usize,
LogicalCpuId::BSP,
);
// Set up IDT
idt::init_paging_bsp();