x86_64: implement high/low split

1 files changed, 66 insertions, 36 deletions

diff --git a/arch/x86_64/src/boot/boot32.S b/arch/x86_64/src/boot/boot32.S
index 7e6c2ae..3039f38 100644
--- a/arch/x86_64/src/boot/boot32.S
+++ b/arch/x86_64/src/boot/boot32.S
@@ -13,9 +13,13 @@ multiboot_information_pointer: .skip 8
 
 .align 4096
 
-page_map_level_4: .skip 512 * 8
-page_map_level_3: .skip 512 * 8
-page_map_level_2: .skip 512 * 8
+page_maps_start:
+page_map_level_4:      .skip 512 * 8
+page_map_level_3_high: .skip 512 * 8
+page_map_level_3_low:  .skip 512 * 8
+page_map_level_2:      .skip 512 * 8
+page_maps_end = .
+page_maps_size = page_maps_end - page_maps_start
 
 /**
  * @brief Storage for the bootstrap stack.
@@ -40,9 +44,9 @@ global_descriptor_table:
 global_descriptor_table_null = . - global_descriptor_table
 .quad 0
 global_descriptor_table_code = . - global_descriptor_table
-.quad GDT_ACCESSED | GDT_READ_WRITE | GDT_EXECUTABLE | GDT_DESCRIPTOR_TYPE | GDT_PRESENT | GDT_LONG_MODE
+.quad GDT_READ_WRITE | GDT_EXECUTABLE | GDT_DESCRIPTOR_TYPE | GDT_PRESENT | GDT_LONG_MODE | (1 << 55)
 global_descriptor_table_data = . - global_descriptor_table
-.quad GDT_ACCESSED | GDT_READ_WRITE | GDT_DESCRIPTOR_TYPE | GDT_PRESENT
+.quad GDT_READ_WRITE | GDT_DESCRIPTOR_TYPE | GDT_PRESENT | (1 << 54) | (1 << 55)
 global_descriptor_table_end:
 
 message_prefix_panic:                    .string  "Panic: "
@@ -125,7 +129,10 @@ _start:
     call _assert_cpuid_instruction_is_supported
     call _assert_cpu_supports_long_mode
 
+    push $HUGE_PAGES_TO_MAP
     call _prepare_page_maps
+    add $4, %esp
+
     call _enable_paging
     call _enable_sse
     call _reload_gdt
@@ -302,51 +309,74 @@ _assert_cpu_supports_long_mode:
 /**
  * @brief Prepare a recursive page map hierarchy
  *
- * We map all physical memory we were loaded in plus one additional page. The
- * mapping is done in terms of huge pages (2 MiB per page) to save on required
- * page map entries.
- *
+ * @param ebp+8 The number of huge pages to map
  * @return void
  */
 _prepare_page_maps:
     pie_function_start
-    push %ebx
 
-    /* Map the P4 table recursively */
-    lea (page_map_level_4 - 0b)(%esi), %eax
-    mov %eax, %ebx
-    or $0b11, %ebx
-    mov %ebx, (511 * 8)(%eax)
-
-    /* Add an entry to the PML4, pointing to the PML3 */
-    lea (page_map_level_3 - 0b)(%esi), %ebx
-    or $0b11, %ebx
-    mov %ebx, (((0x0000000000100000 >> 39) & 0x1ff) * 8)(%eax)
-
-    /* Add an entry to the PML3, pointing to the PML2 */
-    lea (page_map_level_3 - 0b)(%esi), %eax
-    lea (page_map_level_2 - 0b)(%esi), %ebx
-    or $0b11, %ebx
-    mov %ebx, (((0x0000000000100000 >> 30) & 0x1ff) * 8)(%eax)
-
-    /* Add entries for huge pages to the PML2 */
     push %edi
-    lea (page_map_level_2 - 0b)(%esi), %ebx
-    mov $HUGE_PAGES_TO_MAP, %edi
-    xor %ecx, %ecx
+
+    call _clear_page_map_memory
+
+    lea (page_map_level_4 - 0b)(%esi), %edi
+    mov %edi, %eax
+    or $0b11, %eax
+    mov %eax, (510 * 8)(%edi)
+
+    lea (page_map_level_3_low - 0b)(%esi), %eax
+    or $0b11, %eax
+    mov %eax, (%edi)
+
+    lea (page_map_level_3_high - 0b)(%esi), %eax
+    or $0b11, %eax
+    mov %eax, (511 * 8)(%edi)
+
+    lea (page_map_level_3_low - 0b)(%esi), %edi
+    lea (page_map_level_2 - 0b)(%esi), %eax
+    or $0b11, %eax
+    mov %eax, (%edi)
+
+    lea (page_map_level_3_high - 0b)(%esi), %edi
+    lea (page_map_level_2 - 0b)(%esi), %eax
+    or $0b11, %eax
+    mov %eax, (510 * 8)(%edi)
+
+    lea (page_map_level_2 - 0b)(%esi), %edi
+    mov 8(%ebp), %ecx
 
 1:
+    dec %ecx
     mov $(1 << 21), %eax
     mul %ecx
     or $0b10000011, %eax
-    mov %eax, (%ebx, %ecx, 8)
+    mov %eax, (%edi, %ecx, 8)
 
-    inc %ecx
-    cmp %edi, %ecx
-    jne 1b
+    test %ecx, %ecx
+    jnz 1b
 
     pop %edi
-    pop %ebx
+
+    pie_function_end
+
+/**
+ * @brief Clear all page map memory by filling it with 0s.
+ *
+ * @return void
+ */
+_clear_page_map_memory:
+    pie_function_start
+
+    push %edi
+
+    xor %eax, %eax
+    mov $page_maps_size, %ecx
+    shr $2, %ecx
+    lea (page_maps_start - 0b)(%esi), %edi
+    rep stosl
+
+    pop %edi
+
     pie_function_end
 
 /**