From bdea7f553a782f2ebdfdf3bc54f904f936e3befd Mon Sep 17 00:00:00 2001
From: Jeremy Soller <jeremy@system76.com>
Date: Fri, 15 Jan 2021 06:57:02 -0700
Subject: [PATCH] Remove PRESENT flag from aarch64 descriptors
---
src/arch/aarch64/paging/entry.rs | 10 ++++------
src/arch/aarch64/paging/mapper.rs | 6 +-----
src/arch/aarch64/paging/mod.rs | 6 +++---
src/arch/aarch64/paging/table.rs | 5 ++---
4 files changed, 10 insertions(+), 17 deletions(-)
diff --git a/src/arch/aarch64/paging/entry.rs b/src/arch/aarch64/paging/entry.rs
index cee4701e..249732e1 100644
--- a/src/arch/aarch64/paging/entry.rs
+++ b/src/arch/aarch64/paging/entry.rs
@@ -18,7 +18,6 @@ bitflags! {
const VALID = 1 << 0;
const TABLE = 1 << 1;
const AF = 1 << 10; /* NOTE: TableDescriptors don't actually have an AF bit! */
- const PRESENT = 1 << 58; /* ARM ARM says this is an IGNORED bit, so using it here should be OK */
const PXNTABLE = 1 << 59;
const UXNTABLE = 1 << 60;
const APTABLE_0 = 1 << 61;
@@ -48,7 +47,6 @@ bitflags! {
const CONTIGUOUS = 1 << 52;
const PXN = 1 << 53;
const UXN = 1 << 54;
- const PRESENT = 1 << 58; /* Assuming DBM can be overloaded as PRESENT */
}
}
@@ -108,7 +106,7 @@ impl Entry {
/// Get the associated frame, if available, for a level 4, 3, or 2 page
pub fn pointed_frame(&self) -> Option<Frame> {
- if self.page_table_entry_flags().contains(TableDescriptorFlags::PRESENT) {
+ if self.page_table_entry_flags().contains(TableDescriptorFlags::VALID) {
Some(Frame::containing_address(self.address()))
} else {
None
@@ -117,7 +115,7 @@ impl Entry {
/// Get the associated frame, if available, for a level 1 page
pub fn pointed_frame_at_l1(&self) -> Option<Frame> {
- if self.page_descriptor_entry_flags().contains(PageDescriptorFlags::PRESENT) {
+ if self.page_descriptor_entry_flags().contains(PageDescriptorFlags::VALID) {
Some(Frame::containing_address(self.address()))
} else {
None
@@ -142,10 +140,10 @@ impl Entry {
debug_assert!(frame.start_address().data() & !ADDRESS_MASK == 0);
// ODDNESS Alert: We need to set the AF bit - despite this being a TableDescriptor!!!
// The Arm ARM says this bit (bit 10) is IGNORED in Table Descriptors so hopefully this is OK
- let mut translated_flags = TableDescriptorFlags::AF | TableDescriptorFlags::VALID | TableDescriptorFlags::TABLE;
+ let mut translated_flags = TableDescriptorFlags::AF | TableDescriptorFlags::TABLE;
if flags.contains(EntryFlags::PRESENT) {
- translated_flags.insert(TableDescriptorFlags::PRESENT);
+ translated_flags.insert(TableDescriptorFlags::VALID);
}
self.0 = (frame.start_address().data() as u64) | translated_flags.bits() | (self.0 & COUNTER_MASK);
diff --git a/src/arch/aarch64/paging/mapper.rs b/src/arch/aarch64/paging/mapper.rs
index 3c2fe45d..9828b99b 100644
--- a/src/arch/aarch64/paging/mapper.rs
+++ b/src/arch/aarch64/paging/mapper.rs
@@ -110,8 +110,6 @@ impl Mapper {
let p1 = p2.next_table_create(page.p2_index());
let mut translated_flags: PageDescriptorFlags = PageDescriptorFlags::VALID | PageDescriptorFlags::PAGE | PageDescriptorFlags::AF;
- translated_flags.insert(PageDescriptorFlags::PRESENT);
-
if flags.contains(EntryFlags::NO_EXECUTE) {
match page.start_address().get_type() {
VAddrType::User => {
@@ -165,8 +163,6 @@ impl Mapper {
let frame = p1[page.p1_index()].pointed_frame_at_l1().expect("failed to remap: not mapped");
let mut translated_flags: PageDescriptorFlags = PageDescriptorFlags::VALID | PageDescriptorFlags::PAGE | PageDescriptorFlags::AF;
- translated_flags.insert(PageDescriptorFlags::PRESENT);
-
if flags.contains(EntryFlags::NO_EXECUTE) {
match page.start_address().get_type() {
VAddrType::User => {
@@ -301,7 +297,7 @@ impl Mapper {
.and_then(|p2| p2.next_table(page.p2_index()))
.and_then(|p1| Some(p1[page.p1_index()].page_descriptor_entry_flags())) {
- if flags.contains(PageDescriptorFlags::PRESENT) {
+ if flags.contains(PageDescriptorFlags::VALID) {
translated_flags.insert(EntryFlags::PRESENT);
}
diff --git a/src/arch/aarch64/paging/mod.rs b/src/arch/aarch64/paging/mod.rs
index 73cc6dbf..b52c79dc 100644
--- a/src/arch/aarch64/paging/mod.rs
+++ b/src/arch/aarch64/paging/mod.rs
@@ -301,7 +301,7 @@ impl ActivePageTable {
// overwrite recursive mapping
self.p4_mut()[crate::RECURSIVE_PAGE_PML4].page_table_entry_set(
table.p4_frame.clone(),
- TableDescriptorFlags::PRESENT | TableDescriptorFlags::VALID | TableDescriptorFlags::TABLE,
+ TableDescriptorFlags::VALID | TableDescriptorFlags::TABLE,
);
self.flush_all();
@@ -311,7 +311,7 @@ impl ActivePageTable {
// restore recursive mapping to original p4 table
p4_table[crate::RECURSIVE_PAGE_PML4].page_table_entry_set(
backup,
- TableDescriptorFlags::PRESENT | TableDescriptorFlags::VALID | TableDescriptorFlags::TABLE,
+ TableDescriptorFlags::VALID | TableDescriptorFlags::TABLE,
);
self.flush_all();
}
@@ -357,7 +357,7 @@ impl InactivePageTable {
// set up recursive mapping for the table
table[crate::RECURSIVE_PAGE_PML4].page_table_entry_set(
frame.clone(),
- TableDescriptorFlags::PRESENT | TableDescriptorFlags::VALID | TableDescriptorFlags::TABLE
+ TableDescriptorFlags::VALID | TableDescriptorFlags::TABLE
);
}
temporary_page.unmap(active_table);
diff --git a/src/arch/aarch64/paging/table.rs b/src/arch/aarch64/paging/table.rs
index 88273159..ccedf7e4 100644
--- a/src/arch/aarch64/paging/table.rs
+++ b/src/arch/aarch64/paging/table.rs
@@ -121,8 +121,7 @@ impl<L> Table<L> where L: HierarchicalLevel {
self.increment_entry_count();
/* Allow users to go down the page table, implement permissions at the page level */
- let mut perms = TableDescriptorFlags::PRESENT;
- perms |= TableDescriptorFlags::VALID;
+ let mut perms = TableDescriptorFlags::VALID;
perms |= TableDescriptorFlags::TABLE;
self[index].page_table_entry_set(frame, perms);
@@ -133,7 +132,7 @@ impl<L> Table<L> where L: HierarchicalLevel {
fn next_table_address(&self, index: usize) -> Option<usize> {
let entry_flags = self[index].page_table_entry_flags();
- if entry_flags.contains(TableDescriptorFlags::PRESENT) {
+ if entry_flags.contains(TableDescriptorFlags::VALID) {
let table_address = self as *const _ as usize;
if (table_address & KSPACE_ADDR_MASK) != 0 {
Some((table_address << 9) | (index << 12))
--
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