calculate memmap entry len, dump entries

boot1.s

@@ -250,7 +250,11 @@ main:
   call mem_detect
   jc .mem_detect_fail
 
+  call print_memmap
+
+.hlt_loop:
   hlt
+  jmp .hlt_loop
 
 .mem_detect_fail:
   panic PANIC_TYPE_MEM_DETECT
@@ -605,6 +609,38 @@ nybble_to_hex_char:
   ret
 
 
+; Copy a null-terminated string from ds:cx to es:ax.
+; - es: output buffer segment
+; - ax: output buffer offset
+; - ds: input buffer segment
+; - cx: input buffer offset
+; Return:
+; - ax: the address of the null terminator that was written
+; Clobber: none
+strcpy:
+  fnstart
+  push si
+  push di
+
+  mov di, ax
+  mov si, cx
+  
+.loop:
+  mov al, [si]
+  mov es:[di], al
+  test al, al
+  jz .done
+  inc si
+  inc di
+  jmp .loop
+
+.done:
+  mov ax, di
+  pop di
+  pop si
+  fnret
+
+
 ; Check whether the A20 line is enabled. Writes to the boot sector identifier.
 ; Arguments: none
 ; Return:
@@ -711,10 +747,6 @@ enable_a20_intel_8042:
 
 
 mem_detect:
-  %if MEMMAP_CAP < 1
-  %error "memmap buffer too small"
-  %endif
-
   fnstart
   push es
 
@@ -731,39 +763,43 @@ mem_detect:
   xor ebx, ebx
   ; Buffer (es:di)
   mov di, MEMMAP
-  mov dword [di + 0x20], 0x1
+
-  ; Entry size
+.loop:
-  mov ecx, MEMMAP_ENT_SIZE
+  cmp word [GLOBALS + MEMMAP_ENTRIES], MEMMAP_CAP
+  jae .done
+
+  ; Init extended field to 0x1 in case e820 doesn't populate it.  
+  mov dword [di + MEMMAP_ENT_FIELD_EXT], 0x1
+  ; Size of entry for e820 to write
+  mov ecx, E820_ENTRY_SIZE
   ; Magic number
   mov edx, E820_MAGIC
   ; Detect memory
   mov eax, 0xe820
   clc
   int 0x15
-  jc .fail
+  ; Carry flag will be set if we'd already reached the end of the entries.
+  jc .done
+
+  ; Test magic number
   cmp eax, E820_MAGIC
   jne .fail
 
   inc word [GLOBALS + MEMMAP_ENTRIES]
 
-.loop:
+  ; Calculate and cache the entry end address.
-  cmp word [GLOBALS + MEMMAP_ENTRIES], MEMMAP_CAP
+  mov eax, [di + MEMMAP_ENT_FIELD_BASE]
-  jae .done
+  add eax, [di + MEMMAP_ENT_FIELD_LEN]
-
+  mov [di + MEMMAP_ENT_FIELD_END], eax
-  add di, MEMMAP_ENT_SIZE
+  mov eax, [di + MEMMAP_ENT_FIELD_BASE + 4]
-  mov dword [di + 0x20], 0x1
+  adc eax, [di + MEMMAP_ENT_FIELD_LEN + 4]
-  mov ecx, MEMMAP_ENT_SIZE
+  mov [di + MEMMAP_ENT_FIELD_END + 4], eax
-  mov eax, 0xe820
-  clc
-  int 0x15
-  ; Carry flag will be set if we'd already reached the end of the entries.
-  jc .done
-
-  inc word [GLOBALS + MEMMAP_ENTRIES]
 
+  ; e820 _may_ return ebx=0 once we reach the last entry.
   test ebx, ebx
   jz .done
 
+  add di, MEMMAP_ENT_SIZE
   jmp .loop
 
 .fail:
@@ -771,6 +807,9 @@ mem_detect:
   jmp .return
 
 .done:
+  mov ax, [GLOBALS + MEMMAP_ENTRIES]
+  test ax, ax
+  jz .fail
   clc
 
 .return:
@@ -778,12 +817,107 @@ mem_detect:
   fnret
 
 
+print_memmap:
+  fnstart
+
+  sub sp, VGA_WIDTH
+  push eax
+  push ebx
+  push ecx
+  push edx
+
+  mov si, MEMMAP
+  mov dx, [GLOBALS + MEMMAP_ENTRIES]
+
+.loop:
+  test dx, dx
+  jz .done
+  dec dx
+  
+  push es
+  mov ax, ss
+  mov es, ax
+
+  ; Calculate region end
+  ; mov eax, [si]
+  ; mov ecx, [si + 8]
+  ; add eax, ecx
+  ; push eax
+  ; mov eax, [si + 4]
+  ; mov eax, [si + 12]
+  ; adc eax, ecx
+  ; push eax
+
+  lea ax, [bp - VGA_WIDTH]
+  
+  mov cx, msg_memmap_base
+  call strcpy
+
+  mov ecx, [si + MEMMAP_ENT_FIELD_BASE + 4]
+  call dump_reg
+  mov ecx, [si + MEMMAP_ENT_FIELD_BASE]
+  call dump_reg
+  
+  mov cx, msg_sep
+  call strcpy
+  mov cx, msg_memmap_len
+  call strcpy
+  
+  mov ecx, [si + MEMMAP_ENT_FIELD_LEN + 4]
+  call dump_reg
+  mov ecx, [si + MEMMAP_ENT_FIELD_LEN]
+  call dump_reg
+
+  mov cx, msg_sep
+  call strcpy
+  mov cx, msg_memmap_end
+  call strcpy
+  
+  mov ecx, [si + MEMMAP_ENT_FIELD_END + 4]
+  call dump_reg
+  mov ecx, [si + MEMMAP_ENT_FIELD_END]
+  call dump_reg
+
+  mov cx, msg_sep
+  call strcpy
+  mov cx, msg_memmap_type
+  call strcpy
+
+  mov ecx, [si + MEMMAP_ENT_FIELD_TYPE]
+  call dump_reg
+
+  mov bx, ax
+  mov byte [bx], 0
+
+  lea ax, [bp - VGA_WIDTH]
+  call vga_println
+
+  pop es
+  add si, MEMMAP_ENT_SIZE
+  jmp .loop
+
+.done:
+  pop edx
+  pop ecx
+  pop ebx
+  pop eax
+  add sp, VGA_WIDTH
+  fnret
+
+
 msg_boot1_loaded db "boot1 loaded. hello!", 0
 msg_a20_enabled  db "a20 enabled", 0
 msg_a20_disabled db "a20 not enabled", 0
 msg_a20_8042     db "trying 8042", 0
 msg_panic        db "panic!", 0
 
+msg_sep         db ",", 0
+msg_memmap_base db "base=", 0
+msg_memmap_end  db "end=", 0
+msg_memmap_len  db "len=", 0
+msg_memmap_type db "type=", 0
+msg_memmap_ext  db "ext=", 0
+
 msg_reg_eip   db "eip", 0
 msg_reg_eax   db "eax", 0
 msg_reg_ebx   db "ebx", 0

defines.s

@@ -3,7 +3,7 @@
 
 %define MEMMAP                0x6a00
 %define MEMMAP_END            BOOT0_LOADPOINT
-%define MEMMAP_ENT_SIZE 24
+%define MEMMAP_ENT_SIZE       32
 %define MEMMAP_CAP            ((MEMMAP_END - MEMMAP) / MEMMAP_ENT_SIZE)
 
 %define GLOBALS     0x4000
@@ -33,6 +33,15 @@
 
 ; ASCII string "SMAP", which is used by e820 as a magic number argument and return value.
 %define E820_MAGIC 0x534d4150
+; Size of entry returned by e820. This is less than MEMMAP_ENT_SIZE because we add some fields of
+; our own.
+%define E820_ENTRY_SIZE 24
+
+%define MEMMAP_ENT_FIELD_BASE 0x00
+%define MEMMAP_ENT_FIELD_LEN  0x08
+%define MEMMAP_ENT_FIELD_TYPE 0x10
+%define MEMMAP_ENT_FIELD_EXT  0x14
+%define MEMMAP_ENT_FIELD_END  0x18
 
 ; boot0 base stack frame variable offsets / globals
 ; (we use the same offsets once we copy the variables to the globals section)