diff --git a/cpu/idt.c b/cpu/idt.c
index 218c88d..da94d89 100644
--- a/cpu/idt.c
+++ b/cpu/idt.c
@@ -30,7 +30,7 @@ void set_idt_gate(int n, uint32_t handler) {
 }
 
 // defined in vectors.S
-extern uint32_t default_handlers[];
+extern const uint32_t default_handlers[];
 
 void init_idt() {
     if (default_handlers[0] == 0) {
@@ -41,7 +41,7 @@ void init_idt() {
     }
 }
 
-const char *exception_messages[] = {
+const char * const exception_messages[] = {
     "Division By Zero",
     "Debug",
     "Non Maskable Interrupt",
diff --git a/cpu/vectors.S b/cpu/vectors.S
index 9fd80ed..5c9f42e 100644
--- a/cpu/vectors.S
+++ b/cpu/vectors.S
@@ -37,11 +37,11 @@ vector\i :
     .section .text
     handler \number
 
-    .section .data
+    .section .rodata
     .long vector\number
 .endm
 
-.section .data
+.section .rodata
 .global default_handlers
 default_handlers:
 .set i,0
diff --git a/mbr.S b/mbr.S
index 2451313..dac62bb 100644
--- a/mbr.S
+++ b/mbr.S
@@ -16,7 +16,11 @@ get_drive_geometry:
     mov $8, %ah
     mov boot_drive, %dl
     int $0x13
-    // TODO
+    inc %dh  // number of heads
+    mov %dh, disk_heads
+    and 0x3f, %cl
+    mov %cl, sectors_per_track
+    ret
 
 
 .equ ELF32_ENTRY_OFFSET, 0x18
@@ -42,13 +46,17 @@ load_kernel:
     mov KERNEL_OFFSET + ELF32_ENTRY_OFFSET, %si
     mov %si, entry // store entry point
 
+    #if 0
     mov KERNEL_OFFSET + ELF32_PHNUM_OFFSET, %ax
     dec %ax  // no offset to the first entry
     mulb KERNEL_OFFSET + ELF32_PHENTSIZE_OFFSET
     mov %ax, %di
-
     add KERNEL_OFFSET + ELF32_PHDR_OFFSET, %di
     // now di holds offset to the last phentry
+    #else
+    mov KERNEL_OFFSET + ELF32_PHDR_OFFSET, %di
+    // now di holds offset to the first phentry
+    #endif
     mov KERNEL_OFFSET + ELF32_PHDR_FILESZ_OFFSET(%di), %ax
     add KERNEL_OFFSET + ELF32_PHDR_P_OFFSET(%di), %ax
     sub $0x1000, %ax // we won't load the header
@@ -140,6 +148,10 @@ read_error:
     .balign 2
 entry:
     .word 0
+disk_heads:
+    .byte 0
+sectors_per_track:
+    .byte 0
 
     .balign 4
 gdt_start: