关于 c :Finding Memory Size in Boot without DOS, Windows, Linux

   xor ebx, ebx     ; ebx must be 0 to start
   xor bp, bp       ; keep an entry count in bp
   mov edx, 0x0534D4150 ; Place"SMAP" into edx
   mov eax, 0xe820
   mov [es:di + 20], dword 1    ; force a valid ACPI 3.X entry
   mov ecx, 24      ; ask for 24 bytes
   int 0x15
   jc short .failed1    ; carry set on first call means"unsupported function"
   mov edx, 0x0534D4150 ; Some BIOSes apparently trash this register?
   cmp eax, edx     ; on success, eax must have been reset to"SMAP"
   jne short .failed2
   test ebx, ebx        ; ebx = 0 implies list is only 1 entry long (worthless)
   je short .failed3
   jmp short .jmpin

.e820lp:
   mov eax, 0xe820      ; eax, ecx get trashed on every int 0x15 call
   mov [es:di + 20], dword 1    ; force a valid ACPI 3.X entry
   mov ecx, 24      ; ask for 24 bytes again
   int 0x15
   jc short .e820f      ; carry set means"end of list already reached"
   mov edx, 0x0534D4150 ; repair potentially trashed register

.jmpin:
   jcxz .skipent        ; skip any 0 length entries
   cmp cl, 20       ; got a 24 byte ACPI 3.X response?
   jbe short .notext
   test byte [es:di + 20], 1    ; if so: is the"ignore this data" bit clear?
   je short .skipent

.notext:
   mov ecx, [es:di + 8] ; get lower dword of memory region length
   or ecx, [es:di + 12] ;"or" it with upper dword to test for zero
   jz .skipent      ; if length qword is 0, skip entry
   inc bp           ; got a good entry: ++count, move to next storage spot
   add di, 24

.skipent:
   test ebx, ebx        ; if ebx resets to 0, list is complete
   jne short .e820lp

.e820f:
   mov [mmap_ent], bp   ; store the entry count
   clc          ; there is"jc" on end of list to this point, so the carry must be cleared

   mov ah, 0x0E       ; Teletype command
   mov bh, 0x00       ; Page number
   mov bl, 0x07       ; Attributes (7 == white foreground, black background)
   mov al, mmap_ent   ; Character to print
   int 0x10

   ret

.failed1:
   push eax
   push ebx
   mov ah, 0x0E       ; Teletype command
   mov bh, 0x00       ; Page number
   mov bl, 0x07       ; Attributes (7 == white foreground, black background)
   mov al, 70 ; Character 'F' to print
   int 0x10
   pop ebx
   pop eax

   stc          ;"function unsupported" error exit
   ret

.failed2:
   push eax
   push ebx
   mov ah, 0x0E       ; Teletype command
   mov bh, 0x00       ; Page number
   mov bl, 0x07       ; Attributes (7 == white foreground, black background)
   mov al, 71 ; Character 'G' to print
   int 0x10
   pop ebx
   pop eax

   stc          ;"function unsupported" error exit
   ret

.failed3:
   push eax
   push ebx
   mov ah, 0x0E       ; Teletype command
   mov bh, 0x00       ; Page number
   mov bl, 0x07       ; Attributes (7 == white foreground, black background)
   mov al, 72 ; Character 'H' to print
   int 0x10
   pop ebx
   pop eax

   stc          ;"function unsupported" error exit
   ret

   mmap_ent db 0
   failmsg db 0
   failmem db 'Failed', 0
   ;times 512-($-$$) db 0
   ;dw 0xAA55