Fix mis-flagged page table entries

src/kernel/memory_bootstrap.cpp

@@ -186,9 +186,31 @@ memory_initialize(uint16_t scratch_pages, const void *memory_map, size_t map_len
 
 	page_table *id_pml4 = &tables[0];
 	page_table *id_pdp = &tables[1];
+
+	// Flags: 0  0 0 0 1  1 0 0 0  0 0 1 1 = 0x0183
+	//        |   IGN  |  | | | |  | | | +- Present
+	//        |        |  | | | |  | | +--- Writeable
+	//        |        |  | | | |  | +----- Supervisor only
+	//        |        |  | | | |  +------- PWT (determining memory type for page)
+	//        |        |  | | | +---------- PCD (determining memory type for page)
+	//        |        |  | | +------------ Accessed flag (not accessed yet)
+	//        |        |  | +-------------- Dirty (not dirtied yet)
+	//        |        |  +---------------- Page size (1GiB page)
+	//        |        +------------------- Global
+	//        +---------------------------- PAT (determining memory type for page)
 	for (int i=0; i<512; ++i)
-		id_pdp->entries[i] = (static_cast<uintptr_t>(i) << 30) | 0x18b;
+		id_pdp->entries[i] = (static_cast<uintptr_t>(i) << 30) | 0x0183;
-	id_pml4->entries[511] = reinterpret_cast<uintptr_t>(id_pdp) | 0x10b;
+
+	// Flags: 0 0 0 0  0 0 0 0  0 0 1 1 = 0x0003
+	//        IGNORED  | | | |  | | | +- Present
+	//                 | | | |  | | +--- Writeable
+	//                 | | | |  | +----- Supervisor only
+	//                 | | | |  +------- PWT (determining memory type for pdpt)
+	//                 | | | +---------- PCD (determining memory type for pdpt)
+	//                 | | +------------ Accessed flag (not accessed yet)
+	//                 | +-------------- Ignored
+	//                 +---------------- Reserved 0
+	id_pml4->entries[511] = reinterpret_cast<uintptr_t>(id_pdp) | 0x003;
 
 	// Make sure the page table is finished updating before we write to memory
 	__sync_synchronize();
@@ -218,7 +240,7 @@ memory_initialize(uint16_t scratch_pages, const void *memory_map, size_t map_len
 	pml4 = kutil::offset_pointer(pml4, page_offset);
 
 	kutil::memset(pml4, 0, sizeof(page_table));
-	pml4->entries[511] = reinterpret_cast<uintptr_t>(id_pdp) | 0x10b;
+	pml4->entries[511] = reinterpret_cast<uintptr_t>(id_pdp) | 0x003;
 
 	bootstrap.page_in_kernel(*pm, pml4);
 

src/kernel/page_manager.cpp

@@ -17,6 +17,13 @@ using memory::page_mappable;
 page_manager g_page_manager(g_frame_allocator);
 extern kutil::vm_space g_kspace;
 
+// NB: in 4KiB page table entries, bit 7 isn't pagesize but PAT. Currently this
+// doesn't matter, becasue in the default PAT table, both 000 and 100 are WB.
+constexpr uint64_t sys_page_flags   = 0x183; // global, pagesize, write, present
+constexpr uint64_t sys_table_flags  = 0x003; // write, present
+constexpr uint64_t user_page_flags  = 0x087; // pagesize, user, write, present
+constexpr uint64_t user_table_flags = 0x007; // user, write, present
+
 static uintptr_t
 pt_to_phys(page_table *pt)
 {
@@ -335,7 +342,7 @@ page_manager::check_needs_page(page_table *table, unsigned index, bool user)
 
 	page_table *new_table = get_table_page();
 	for (int i=0; i<512; ++i) new_table->entries[i] = 0;
-	table->entries[index] = pt_to_phys(new_table) | (user ? 0xf : 0xb);
+	table->entries[index] = pt_to_phys(new_table) | (user ? user_table_flags : sys_table_flags);
 }
 
 void
@@ -349,9 +356,7 @@ page_manager::page_in(page_table *pml4, uintptr_t phys_addr, uintptr_t virt_addr
 	page_table_indices idx{virt_addr};
 	page_table *tables[4] = {pml4, nullptr, nullptr, nullptr};
 
-	uint64_t flags = user ?
+	uint64_t flags = user ? user_table_flags : sys_table_flags;
-		0x00f:	// writethru, user, write, present
-		0x10b;	// global, writethru, write, present
 
 	for (; idx[0] < 512; idx[0] += 1) {
 		check_needs_page(tables[0], idx[0], user);