diff --git a/src/memory/paging/mod.rs b/src/memory/paging/mod.rs index 75859d0..fcf39df 100644 --- a/src/memory/paging/mod.rs +++ b/src/memory/paging/mod.rs @@ -1,4 +1,4 @@ -use memory::PAGE_SIZE; +use memory::{PAGE_SIZE, Frame}; mod entry; mod table; @@ -11,3 +11,78 @@ pub type VirtualAddress = usize; pub struct Page { number: usize, } + +impl Page { + pub fn containing_address(address: VirtualAddress) -> Page { + assert!(address < 0x0000_8000_0000_0000 || + address >= 0xffff_8000_0000_0000, + "invalid address: 0x{:x}", address); + Page { number: address / PAGE_SIZE } + } + + fn start_address(&self) -> usize { + self.number * PAGE_SIZE + } + + fn p4_index(&self) -> usize { + (self.number >> 27) & 0o777 + } + fn p3_index(&self) -> usize { + (self.number >> 18) & 0o777 + } + fn p2_index(&self) -> usize { + (self.number >> 9) & 0o777 + } + fn p1_index(&self) -> usize { + (self.number >> 0) & 0o777 + } + +} + +pub fn translate(virtual_address: VirtualAddress) -> Option { + let offset = virtual_address % PAGE_SIZE; + translate_page(Page::containing_address(virtual_address)) + .map(|frame| frame.number * PAGE_SIZE + offset) +} + +fn translate_page(page: Page) -> Option { + use self::entry::HUGE_PAGE; + + let p3 = unsafe { &*table::P4 }.next_table(page.p4_index()); + + let huge_page = || { + p3.and_then(|p3| { + let p3_entry = &p3[page.p3_index()]; + // 1GiB page? + if let Some(start_frame) = p3_entry.pointed_frame() { + if p3_entry.flags().contains(HUGE_PAGE) { + // address must be 1GiB aligned + assert!(start_frame.number % (ENTRY_COUNT * ENTRY_COUNT) == 0); + return Some(Frame { + number: start_frame.number + page.p2_index() * + ENTRY_COUNT + page.p1_index(), + }); + } + } + if let Some(p2) = p3.next_table(page.p3_index()) { + let p2_entry = &p2[page.p2_index()]; + // 2MiB page? + if let Some(start_frame) = p2_entry.pointed_frame() { + if p2_entry.flags().contains(HUGE_PAGE) { + // address must be 2MiB aligned + assert!(start_frame.number % ENTRY_COUNT == 0); + return Some(Frame { + number: start_frame.number + page.p1_index() + }); + } + } + } + None + }) + }; + + p3.and_then(|p3| p3.next_table(page.p3_index())) + .and_then(|p2| p2.next_table(page.p2_index())) + .and_then(|p1| p1[page.p1_index()].pointed_frame()) + .or_else(huge_page) +}