rustubs/arch/x86_64/
paging.rs

1pub mod fault;
2pub mod pagetable;
3use crate::defs;
4use crate::defs::rounddown_4k;
5use crate::defs::P2V;
6use crate::io::*;
7use crate::mm::allocate_4k_zeroed;
8use crate::mm::vmm::VMArea;
9use crate::mm::vmm::VMType;
10use core::arch::asm;
11use core::ops::Range;
12use core::ptr;
13pub use pagetable::*;
14/// for x86_64, return the CR3 register. this is the **physical** address of the
15/// page table root.
16/// TODO: use page root in task struct instead of raw cr3
17#[inline]
18pub fn get_cr3() -> u64 {
19	let cr3: u64;
20	unsafe { asm!("mov {}, cr3", out(reg) cr3) };
21	cr3
22}
23
24/// returns the identically mapped (+ kernel offset) virtual address of the page
25/// table
26#[inline]
27pub fn get_root() -> u64 { P2V(get_cr3()).unwrap() }
28
29/// unsafe as it dereferences raw pointer pt_root. Must make sure it's a valid,
30/// 4k aligned _virtual_ address.
31// TODO use Result type instead of bool so that we can do early return with ?..
32pub unsafe fn map_vma(pt_root: u64, vma: &VMArea, do_copy: bool) -> bool {
33	// create mappings in pagetable
34	let flags = PTEFlags::PRESENT | PTEFlags::WRITABLE | PTEFlags::USER;
35	if !map_range(pt_root, &vma.vm_range, flags) {
36		println!("failed to map range");
37		return false;
38	}
39	if !do_copy {
40		return true;
41	}
42	match vma.backing {
43		VMType::ANOM => {
44			return true;
45		}
46		VMType::FILE(f) => {
47			if !do_copy {
48				return true;
49			}
50			let sz = (vma.vm_range.end - vma.vm_range.start) as usize;
51			sprintln!("copy from {:p} to {:#X}", &f[0], vma.vm_range.start);
52			unsafe {
53				ptr::copy_nonoverlapping(
54					&f[0] as *const u8,
55					vma.vm_range.start as *mut u8,
56					sz,
57				)
58			}
59			return true;
60		}
61		_ => {
62			println!("unknown backing");
63			return false;
64		}
65	}
66}
67
68pub fn map_range(pt_root: u64, r: &Range<u64>, flags: PTEFlags) -> bool {
69	let mut va_aligned = rounddown_4k(r.start);
70	while va_aligned < r.end {
71		if !map_page(pt_root, va_aligned, flags) {
72			println!("failed to map page @ {:#X}", va_aligned);
73			return false;
74		}
75		va_aligned += defs::Mem::PAGE_SIZE;
76	}
77	return true;
78}
79
80/// walk the page table, create missing tables, return mapped physical frame
81pub fn map_page(pt_root: u64, va: u64, _flags: PTEFlags) -> bool {
82	let pt = pt_root as *mut Pagetable;
83	if !defs::is_aligned_4k(va) {
84		println!("not aligned");
85		return false;
86	}
87	let flags: u64 = _flags.bits();
88	let l4idx = pagetable::p4idx(va) as usize;
89	let l3idx = pagetable::p3idx(va) as usize;
90	let l2idx = pagetable::p2idx(va) as usize;
91	let l1idx = pagetable::p1idx(va) as usize;
92	let mut require_new = false;
93	unsafe {
94		let l4_ent = &mut (*pt).entries[l4idx];
95		let l3_tbl: *mut Pagetable;
96		if l4_ent.is_unused() || require_new {
97			l3_tbl = allocate_4k_zeroed() as *mut Pagetable;
98			l4_ent.entry = defs::V2P(l3_tbl as u64).unwrap() | flags;
99			require_new = true
100		} else {
101			l3_tbl = defs::P2V(l4_ent.addr()).unwrap() as *mut Pagetable;
102		}
103		let l3_ent = &mut (*l3_tbl).entries[l3idx];
104		let l2_tbl: *mut Pagetable;
105		if l3_ent.is_unused() || require_new {
106			l2_tbl = allocate_4k_zeroed() as *mut Pagetable;
107			l3_ent.entry = defs::V2P(l2_tbl as u64).unwrap() | flags;
108			require_new = true
109		} else {
110			l2_tbl = defs::P2V(l3_ent.addr()).unwrap() as *mut Pagetable;
111		}
112		let l2_ent = &mut (*l2_tbl).entries[l2idx];
113		let l1_tbl: *mut Pagetable;
114		if l2_ent.is_unused() || require_new {
115			l1_tbl = allocate_4k_zeroed() as *mut Pagetable;
116			l2_ent.entry = defs::V2P(l1_tbl as u64).unwrap() | flags;
117			require_new = true
118		} else {
119			l1_tbl = defs::P2V(l2_ent.addr()).unwrap() as *mut Pagetable;
120		}
121		let pte = &mut (*l1_tbl).entries[l1idx];
122		if pte.is_unused() || require_new {
123			let page = allocate_4k_zeroed();
124			pte.entry = defs::V2P(page).unwrap() | flags;
125		} else {
126			// TODO we need to free this frame
127			panic!("PTE already taken: {:#X}", pte.entry);
128		}
129		// flush tlb
130		asm!("invlpg [{0}]", in(reg) va);
131	}
132	return true;
133}
rustubs/arch/x86_64/paging.rs

rustubs/arch/x86_64/
paging.rs
