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Don't override attributes when creating a new paging table

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This commit is contained in:
Sam Tebbs 2020-07-26 14:29:42 +01:00
parent b4cab2922c
commit 154f7c6d6c
1 changed files with 37 additions and 23 deletions
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44
src/kernel/arch/x86/paging.zig
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@ -198,6 +198,20 @@ fn mapDirEntry(dir: *Directory, virt_start: usize, virt_end: usize, phys_start:
const entry = virtToDirEntryIdx(virt_start); const entry = virtToDirEntryIdx(virt_start);
var dir_entry = &dir.entries[entry]; var dir_entry = &dir.entries[entry];
// Only create a new table if one hasn't already been created for this dir entry.
// Prevents us from overriding previous mappings.
var table: *Table = undefined;
if (dir.tables[entry]) |tbl| {
table = tbl;
} else {
// Create a table and put the physical address in the dir entry
table = &(try allocator.alignedAlloc(Table, @truncate(u29, PAGE_SIZE_4KB), 1))[0];
@memset(@ptrCast([*]u8, table), 0, @sizeOf(Table));
const table_phys_addr = @ptrToInt(mem.virtToPhys(table));
dir_entry.* |= DENTRY_PAGE_ADDR & table_phys_addr;
dir.tables[entry] = table;
}
setAttribute(dir_entry, DENTRY_PRESENT); setAttribute(dir_entry, DENTRY_PRESENT);
setAttribute(dir_entry, DENTRY_WRITE_THROUGH); setAttribute(dir_entry, DENTRY_WRITE_THROUGH);
clearAttribute(dir_entry, DENTRY_4MB_PAGES); clearAttribute(dir_entry, DENTRY_4MB_PAGES);
@ -220,20 +234,6 @@ fn mapDirEntry(dir: *Directory, virt_start: usize, virt_end: usize, phys_start:
setAttribute(dir_entry, DENTRY_CACHE_DISABLED); setAttribute(dir_entry, DENTRY_CACHE_DISABLED);
} }
// Only create a new table if one hasn't already been created for this dir entry.
// Prevents us from overriding previous mappings.
var table: *Table = undefined;
if (dir.tables[entry]) |tbl| {
table = tbl;
} else {
// Create a table and put the physical address in the dir entry
table = &(try allocator.alignedAlloc(Table, @truncate(u29, PAGE_SIZE_4KB), 1))[0];
@memset(@ptrCast([*]u8, table), 0, @sizeOf(Table));
const table_phys_addr = @ptrToInt(mem.virtToPhys(table));
dir_entry.* |= DENTRY_PAGE_ADDR & table_phys_addr;
dir.tables[entry] = table;
}
// Map the table entries within the requested space // Map the table entries within the requested space
var virt = virt_start; var virt = virt_start;
var phys = phys_start; var phys = phys_start;
@ -498,7 +498,8 @@ test "virtToTableEntryIdx" {
test "mapDirEntry" { test "mapDirEntry" {
var allocator = std.heap.page_allocator; var allocator = std.heap.page_allocator;
var dir: Directory = Directory{ .entries = [_]DirectoryEntry{0} ** ENTRIES_PER_DIRECTORY, .tables = [_]?*Table{null} ** ENTRIES_PER_DIRECTORY }; var dir: Directory = Directory{ .entries = [_]DirectoryEntry{0} ** ENTRIES_PER_DIRECTORY, .tables = [_]?*Table{null} ** ENTRIES_PER_DIRECTORY };
var phys: usize = 0 * PAGE_SIZE_4MB; {
const phys: usize = 0 * PAGE_SIZE_4MB;
const phys_end: usize = phys + PAGE_SIZE_4MB; const phys_end: usize = phys + PAGE_SIZE_4MB;
const virt: usize = 1 * PAGE_SIZE_4MB; const virt: usize = 1 * PAGE_SIZE_4MB;
const virt_end: usize = virt + PAGE_SIZE_4MB; const virt_end: usize = virt + PAGE_SIZE_4MB;
@ -508,6 +509,19 @@ test "mapDirEntry" {
const entry = dir.entries[entry_idx]; const entry = dir.entries[entry_idx];
const table = dir.tables[entry_idx] orelse unreachable; const table = dir.tables[entry_idx] orelse unreachable;
checkDirEntry(entry, virt, virt_end, phys, .{ .kernel = true, .writable = true, .cachable = true }, table, true); checkDirEntry(entry, virt, virt_end, phys, .{ .kernel = true, .writable = true, .cachable = true }, table, true);
}
{
const phys: usize = 7 * PAGE_SIZE_4MB;
const phys_end: usize = phys + PAGE_SIZE_4MB;
const virt: usize = 8 * PAGE_SIZE_4MB;
const virt_end: usize = virt + PAGE_SIZE_4MB;
try mapDirEntry(&dir, virt, virt_end, phys, phys_end, .{ .kernel = false, .writable = false, .cachable = false }, allocator);
const entry_idx = virtToDirEntryIdx(virt);
const entry = dir.entries[entry_idx];
const table = dir.tables[entry_idx] orelse unreachable;
checkDirEntry(entry, virt, virt_end, phys, .{ .kernel = false, .writable = false, .cachable = false }, table, true);
}
} }
test "mapDirEntry returns errors correctly" { test "mapDirEntry returns errors correctly" {