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;++;; Module name;; su.asm;; Author;; Thomas Parslow (tomp) Jan-15-91;; Description;; Startup module for the 386 NT OS loader.;; Exported Procedures;; EnableProtectPaging;; Notes; NT386 Boot Loader program. This assembly file is required in; order to link C modules into a "/TINY" (single segment) memory; model.;;; This file does the following:; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~; 1) Defines the entry point for the boot loader's startup program; 2) Computes what values should actually be in the DS and SS registers.; 3) Provides the int bios functionality; 4) Provides 386/486 mode (protect/paging) switching code.;; The OS/2 bootstrap routine (boot sector) loads the boot loader program at; real-mode address 2000:0000 with the following register values:;; CS = 2000; IP = 0000; DS = 07C0; ES = 1000; SS = 0000; SP = 7C00;; Build Notes:; ~~~~~~~~~~~~; The microsoft C compiler will not produce "tiny" model programs. In the; tiny model, the entire program consists of only one segment. The small; model produced by our compilers consists of two segments: DGROUP and _TEXT.; If you convert a small model program into a tiny model program, DS (which; should point to DGROUP (bss,const,data) will always be wrong. For this reason; we need an assembly module to do a simple run-time fixup on SS and DS. To; guarantee that DS will point to DGROUP no matter where os2ldr is loaded,; the paragraph (shifted right four bits) offset of DGROUP from _TEXT must; be added to the value in CS to compute DS and SS.;; We get the linker to fixup the offset of the beginning of the dgroup segment; relative to the beginning of the code segment and it's this value added; to the value in CS that allows us to build a "tiny" model program in C; without a lot of munging around in order to get the data reference offsets; in the code correct.;; If the _TEXT:DGROUP fixup appears in other files (which it does), the linker; will not compute the correct value unless the accumulated data pointer is; zero when it gets there. Therefore, no data should be placed in the data segment; until after all instances of _TEXT:DGROUP have been encountered by the linker.; The linker processes files from right to left on the command line.;; A Note About Stacks; Initially we run on our internal stack (SuStack) which is only 160 bytes deep; but seems to do the trick. Then we have to have a separate double fault stack.; This stack can be in the middle of the stack/data segment. It will step on; the loader image, but that's ok since the fault was either caused by 16bit; code (which won't be in the loader image) or, it was caused by the 32bit; loader (which has already been relocated) so we won't be stepping on code; that may have caused the fault. And finally, we have the "call back" stack; which starts at the top of the stack/data segment. We use this during; all call backs since the original loader source is no longer needed and; this'll give us plenty of stack for bios calls etc.;;--
DoubleWord struclsw dw ?msw dw ?DoubleWord ends
;; This is the structure used to pass all shared data between the boot sector; and NTLDR.;
SHARED struc ReadClusters dd ? ; function pointer ReadSectors dd ? ; function pointer
SectorBase dd ? ; starting sector ; for ReadSectors ; callbackSHARED ends
BPB struc BytesPerSector dw ? SectorsPerCluster db ? ReservedSectors dw ? Fats db ? DirectoryEntries dw ? Sectors dw ? Media db ? FatSectors dw ? SectorsPerTrack dw ? Heads dw ? HiddenSectors dd ? SectorsLong dd ?;; The following byte is NOT part of the BPB but is set by SYS and format;
BootDriveNumber db ?BPB ends
SU_CODEMODULE equ 1 ; Identifies this module to "su.inc"include su.incinclude macro.inc
extrn _BootRecord:wordextrn _puts:nearextrn _MemoryDescriptorList:nearextrn _InsertDescriptor:near
MAXREAD EQU 10000hMAXSECTORS EQU MAXREAD/0200h
_TEXT segment para use16 public 'CODE' ASSUME CS: _TEXT, DS: DGROUP, SS: DGROUP.386p
;; Run-time fixups for stack and data segment;
public StartStart:;; The FAT boot sector only reads in the first 512 bytes of NTLDR. This is; the module that contains those 512 bytes, so we are now responsible for; loading the rest of the file. Other filesystems (i.e. HPFS, NTFS, RIPL); will load the whole file, so the default entrypoint branches around the; FAT-specific code.; jmp RealStart
FatBegin:.386;; If we're here, we've booted off a FAT system and we must load the rest; of NTLDR at 2000:0200 (right behind this sector) NTLDR passes us the; following:; BX = Starting Cluster Number of NTLDR; DL = INT 13h drive number we've booted from; DS:SI -> boot media's BPB; DS:DI -> argument structure (see above struc definition);;; Save away the boot drive and the starting cluster number; push dx push bx
;; Blast the FAT into memory at 6000:0000 - 8000:0000;
.386 push 06000h.8086 pop es xor bx,bx ; (es:bx) = 6000:0000 mov cx,ds:[si].ReservedSectors mov ds:[di].SectorBase.msw,0 mov ds:[di].SectorBase.lsw,cx ; set up Sector Base
mov ax,ds:[si].FatSectors ; (al) = # Sectors to read cmp ax,080h jbe FatLt64k
; The FAT is > 64k, so we read the first 64k chunk, then the rest.; (A 16-bit FAT can't be bigger than 128k)
push cx mov ax,080h ; (al) = # of sectors to read call ds:[di].ReadSectors pop cx ; (cx) = previous SectorBase.386 push 07000h.8086 pop es xor bx,bx ; (es:bx) = 7000:0000 mov ax,ds:[si].FatSectors sub ax,080h ; (ax) = # Sectors left to read add cx,080h ; (cx) = SectorBase for next read mov ds:[di].SectorBase.lsw,cx adc ds:[di].SectorBase.msw,0 ; set up SectorBase
;; (al) = # of sectors to read;FatLt64k: call ds:[di].ReadSectors
;; FAT is in memory, now we restore our starting cluster number; pop dx ; (dx) = starting cluster number xor bx,bx
;; set up FS and GS for reading the FAT;.386 mov ax,6000h mov fs,ax mov ax,7000h mov gs,ax.8086
;; set up ES for reading in the rest of us; push cs pop es
mov ah,MAXSECTORS ; (ah) = number of sectors we can read ; until boundaryFatLoop:;; (dx) = next cluster to load; push dx mov al,ds:[si].SectorsPerCluster ; (al) = number of contiguous sectors ; found sub ah,ds:[si].SectorsPerCluster ; can read before 64k
;; Check to see if we've reached the end of the file; cmp dx,0ffffh jne Fat10
;; The entire file has been loaded. Throw away the saved next cluster,; restore the boot drive, and let NTLDR do its thing.; pop dx pop dx jmp RealStart
Fat10: mov cx,dx;; (dx) = (cx) = last contiguous cluster; (al) = # of contiguous clusters found;
call NextFatEntry;; (dx) = cluster following last contiguous cluster
;; Check to see if the next cluster is contiguous. If not, go load the; contiguous block we've found.; inc cx cmp dx,cx
jne LncLoad
;; Check to see if we've reached the 64k boundary. If so, go load the; contiguous block so far. If not, increment the number of contiguous; sectors and loop again.; cmp ah,0 jne Lnc20 mov ah,MAXSECTORS ; (ah) = number of sectors until ; boundary reached again jmp short LncLoad
Lnc20: add al,ds:[si].SectorsPerCluster sub ah,ds:[si].SectorsPerCluster jmp short Fat10
LncLoad:;; (TOS) = first cluster to load; (dx) = first cluster of next group to load; (al) = number of contiguous sectors; pop cx push dx mov dx,cx mov cx,10 ; (cx) = retry count
;; N.B.; This assumes that we will never have more than 255 contiguous clusters.; Since that would get broken up into chunks that don't cross the 64k; boundary, this is ok.;; (dx) = first cluster to load; (al) = number of contiguous sectors; (TOS) = first cluster of next group to load; (es:bx) = address where clusters should be loaded;FatRetry: push bx push ax push dx push cx
if 0 push dx call PrintDbg mov dx,ax call PrintDbg pop dxendif
call [di].ReadClusters jnc ReadOk;; error in the read, reset the drive and try again;if 0 mov dx, ax call PrintDbgendif mov ax,01h mov al,ds:[si].BootDriveNumber int 13hif 0 mov dx,ax call PrintDbgendif xor ax,ax mov al,ds:[si].BootDriveNumber int 13h
;; pause for a while; xor ax,axFatPause: dec ax jnz FatPause
pop cx pop dx pop ax pop bx
dec cx jnz FatRetry
;; we have re-tried ten times, it still doesn't work, so punt.; push cs pop ds mov si,offset FAT_ERRORFatErrPrint: lodsb or al,al jz FatErrDone mov ah,14 ; write teletype mov bx,7 ; attribute int 10h ; print it jmp FatErrPrint
FatErrDone: jmp $ ; this should be replaced by a mechanism to get a pointer ; passed to us in the param block. since the boot sector msg itself ; is properly localized but this one isn't.FAT_ERROR db 13,10,"Disk I/O error",0dh,0ah,0
ReadOk: pop cx pop dx pop ax pop bx pop dx ; (dx) = first cluster of next group ; to load.
.386;; Convert # of sectors into # of bytes.; mov cl,al xor ch,ch shl cx,9.8086 add bx,cx jz FatLoopDone jmp FatLoop
FatLoopDone:;; (bx) = 0; This means we've just ended on a 64k boundary, so we have to; increment ES to continue reading the file. We are guaranteed to; always end on a 64k boundary and never cross it, because we; will reduce the number of contiguous clusters to read; to ensure that the last cluster read will end on the 64k boundary.; Since we start reading at 0, and ClusterSize will always be a power; of two, a cluster will never cross a 64k boundary.; mov ax,es add ax,01000h mov es,ax mov ah,MAXSECTORS jmp FatLoop
;++;; NextFatEntry - This procedure returns the next cluster in the FAT chain.; It will deal with both 12-bit and 16-bit FATs. It assumes; that the entire FAT has been loaded into memory.;; Arguments:; (dx) = current cluster number; (fs:0) = start of FAT in memory; (gs:0) = start of second 64k of FAT in memory;; Returns:; (dx) = next cluster number in FAT chain; (dx) = 0ffffh if there are no more clusters in the chain;;--NextFatEntry proc near push bx
;; Check to see if this is a 12-bit or 16-bit FAT. The biggest FAT we can; have for a 12-bit FAT is 4080 clusters. This is 6120 bytes, or just under; 12 sectors.;; A 16-bit FAT that's 12 sectors long would only hold 3072 clusters. Thus,; we compare the number of FAT sectors to 12. If it's greater than 12, we; have a 16-bit FAT. If it's less than or equal to 12, we have a 12-bit FAT.; call IsFat12 jnc Next16Fat
Next12Fat: mov bx,dx ; (fs:bx) => temporary index shr dx,1 ; (dx) = offset/2 ; (CY) = 1 need to shift pushf ; = 0 don't need to shift add bx,dx ; (fs:bx) => next cluster number.386 mov dx,fs:[bx] ; (dx) = next cluster number.8086 popf jc shift ; carry flag tells us whether to and dx,0fffh ; mask jmp short N12Tailshift:.386 shr dx,4 ; or shift.8086
N12Tail:;; Check for end of file; cmp dx,0ff8h ; If we're at the end of the file, jb NfeDone ; convert to canonical EOF. mov dx,0ffffh jmp short NfeDone
Next16Fat: add dx,dx ; (dx) = offset jc N16high
mov bx,dx ; (fs:bx) => next cluster number.386 mov dx,fs:[bx] ; (dx) = next cluster number.8086 jmp short N16Tail
N16high: mov bx,dx.386 mov dx,gs:[bx].8086
N16Tail: cmp dx,0fff8h jb NfeDone mov dx,0ffffh ; If we're at the end of the file ; convert to canonical EOF.
NfeDone: pop bx retNextFatEntry endp
;++;; IsFat12 - This function determines whether the BPB describes a 12-bit; or 16-bit FAT.;; Arguments - ds:si supplies pointer to BPB;; Returns; CY set - 12-bit FAT; CY clear - 16-bit FAT;;--IsFat12 proc near
.386 push eax push ebx push ecx push edx
movzx ecx, ds:[si].Sectors or cx,cx jnz if10 mov ecx, ds:[si].SectorsLongif10:;; (ecx) = number of sectors; movzx ebx, byte ptr ds:[si].Fats movzx eax, word ptr ds:[si].FatSectors mul ebx sub ecx,eax
;; (ecx) = (#sectors)-(sectors in FATs); movzx eax, word ptr ds:[si].DirectoryEntries shl eax, 5;; (eax) = #bytes in root dir; mov edx,eax and edx,0ffff0000h div word ptr ds:[si].BytesPerSector sub ecx,eax
;; (ecx) = (#sectors) - (sectors in fat) - (sectors in root dir); movzx eax, word ptr ds:[si].ReservedSectors sub ecx, eax mov eax, ecx movzx ecx, byte ptr ds:[si].SectorsPerCluster xor edx,edx div ecx
cmp eax, 4087 jae if20 stc jmp short if30if20: clcif30: pop edx pop ecx pop ebx pop eax ret.8086IsFat12 endp
PrintDbg proc near push ax push bx push cx
mov cx,4pd10:.386 rol dx,4.8086 mov ah,0eh mov bx,7 mov al,dl and al,0fh add al,'0' cmp al,'9' jbe pd15 add al,'A'-('9'+1)
pd15: int 010h loop pd10
mov ah,0eh mov al,' ' mov bx,7 int 010h pop cx pop bx pop ax
ret
PrintDbg endp
Free EQU 512-($-Start)if Free lt 0 %out FATAL PROBLEM: FAT-specific startup code is greater than
%out 512 bytes. Fix it!
.errendif
RealStart:.386p;; Compute the paragraph needed for DS;if 0 mov ax,0 int 16hendif
mov bx,offset _TEXT:DGROUP ; first calculate offset to data shr bx,4 ; must be para aligned
mov ax,cs ; get base of code add ax,bx ; add paragraph offset to data
mov ss,ax ; ints disabled for next instruct mov sp,offset DGROUP:SuStack ; (sp) = top of internal stack;; Build C stack frame for _SuMain; push dx ; pass bootdisk to main (high byte is ignored);; Make DS point to the paragraph address of DGROUP; mov ds,ax ; ds now points to beginning of DGROUP mov es,ax ; es now points to beginning of DGROUP;; Compute the physical address of the end of the data segment (which; will be the beginning of the prepended loader file).;
movzx edx,ax shl edx,4 add edx,offset DGROUP:_edata mov dword ptr _FileStart,edx
;; Force the upper parts of; of EBP and ESP to be zero in real mode.;
xor bp,bp movzx ebp,bp movzx esp,sp mov [saveDS],ds
call _SuMain ; go to C code to do everything else.
;++; _EnableProtectPaging;; Loads 386 protect mode registers.; Enables 386 protection h/w; Loads pagings registers; Enables 386 paging h/w;;--
public _EnableProtectPaging_EnableProtectPaging proc near;; Sanitize ES and GS and clean out any junk in the upper 16bits; of the flags that may have been left by the bios, before we go protected; push dword ptr 0 popfd mov bx,sp mov dx,[bx+2] ; are we enabling prot/paging for the first time? xor ax,ax mov gs,ax mov es,ax
;; FS must contain the selector of the PCR when we call the kernel; push PCR_Selector pop fs;; Load the gdtr and idtr.; We disable interrupts here since we can't handle interrups with the; idt loaded while were in real mode and before we switch to protmode.
cli lgdt fword ptr [_GDTregister] lidt fword ptr [_IDTregister]
;; We have to stamp the segment portion of any real-mode far pointer with; the corresponding selector values before we go protected.; mov si,offset _ScreenStart mov word ptr [si+2],VideoSelector mov si,offset _vp mov word ptr [si+2],VideoSelector
;; Enable protect and paging mode; mov eax,cr0
; If we're enabling protect mode for the first time, don't turn on paging; because the osloader does all that. However, if we're returning to; protected mode, the page tables are already setup, therefore we do want; to turn paging on. or dx,dx jz only_prot or eax,PROT_MODE + ENABLE_PAGING mov cr0,eax
;; The following JMP must be DWORD-aligned in order to avoid an obscure i386; hardware bug. If not, it is possible (albeit unlikely) that the prefetch; queue can get trashed.;
ALIGN 4 jmp flush
only_prot: or eax,PROT_MODE mov cr0,eax;; Flush the prefetch queue;
ALIGN 4 jmp flushflush:
;; Load CS with the SU module's code selector; push SuCodeSelector push offset cs:restart retf;; Now load DS and SS with the SU module's protect mode data selector.;
restart: mov ax,SuDataSelector mov ds,ax mov ss,ax
;; Load LDT with zero since it will never be used.; xor bx,bx lldt bx
;; Load the Task Register and return to the boot SU module.; or dx,dx jnz epp10
mov bx,TSS_Selector ltr bx
epp10: ret
_EnableProtectPaging endp
.286p;** _biosint;; Rom bios interrupt dispatcher;
public _biosint_biosint proc near
enter 0,0 push di push si push ds push es
; Get pointer to register parameter frame
les di,[bp+4]
; Get requested interrupt number
mov ax,es:[di].intnum
; Check that requested bios interrupt is supported
sub ax,10h ; sub lowest int number supported jnc short bios1 mov es:[di].intnum,FUNCTION_ERROR jmp short biosxbios1: shl ax,1 ; shift if to make it a word offset cmp ax,bios_cnt ; offset beyond end of table? jb short bios2
; Error: requested interrupt not supported
mov es:[di].sax,FUNCTION_ERROR jmp short biosx
bios2: mov bx,ax mov ax,word ptr cs:bios_table[bx] push es ; save seg of address frame push di ; save stack register frame pointer push ax ; address of bios int
mov ax,es:[di].sax mov bx,es:[di].sbx mov cx,es:[di].scx mov dx,es:[di].sdx mov si,es:[di].ssi mov es,es:[di].ses ret ; this sends us to the "int #" instruction
; We return here from the jmp instruction following the int
bios_ret:
pop di ; get address of register parameter frame pop es ; restore segment of parameter frame
bios5: pushf pop es:[di].sfg mov es:[di].sax,ax mov es:[di].sbx,bx mov es:[di].scx,cx mov es:[di].sdx,dx mov es:[di].ssi,si mov es:[di].ses,es
; Restore original registers and return to caller
biosx: pop es pop ds pop si pop di leave ret
_biosint endp
;** Bios Interrupt Table;
bios10: int 10h jmp short bios_retbios11: int 11h jmp short bios_retbios12: int 12h jmp short bios_retbios13: int 13h jmp short bios_retbios14: int 14h jmp short bios_retbios15: int 15h jmp short bios_retbios16: int 16h jmp short bios_retbios17: int 17h jmp short bios_retbios18: int 18h jmp short bios_retbios19: int 19h jmp short bios_ret
bios_table dw bios10,bios11,bios12,bios13,bios14,bios15,bios16,bios17,bios18,bios19
bios_cnt equ $ - bios_table
.386p
;++;; _MoveMemory;; Routine Description;; Moves dwords in memory from source to destination.;; Arguments;; (TOS+4) = number of bytes to move; (TOS+8) = linear address of destination; (TOS+12) = linear address of source;; Notes;; 1) Valid page table entries must already exist for the; source and destination memory.;; 2) ALL memory in the lower one megabyte is assumed to; be identity mapped if used.;; USES ESI, EDI, ECX, FLAGS;;;--
public _MoveMemory_MoveMemory proc near
enter 0,0 push ds push es;; Get source, destination, and count arguments from the stack; Make "count" the number of dwords to move.;
mov esi,dword ptr [bp+4] mov edi,dword ptr [bp+8] mov ecx,dword ptr [bp+12] shr ecx,2
;; Load FLAT selectors into DS and ES;
mov ax,KeDataSelector mov ds,ax mov es,ax
;; Move the block of data.;assume es:FLAT, ds:FLAT
;; move the dwords; cld rep movs dword ptr [edi],dword ptr [esi]
;; move the remaining tail; mov ecx, dword ptr [bp+12] and ecx, 3 rep movs byte ptr [edi],byte ptr [esi]
assume es:nothing, ds:DGROUP
pop es pop ds leave ret
_MoveMemory endp
;++;; _ZeroMemory;; Routine Description;; Writes zeros into memory at the target address.;; Arguments;; (TOS+4) = linear address of target; (TOS+8) = number of bytes to zero;; Notes;; 1) Valid page table entries must already exist for the; source and destination memory.;; 2) ALL memory in the lower one megabyte is assumed to; be identity mapped if used.;; USES ESI, EDI, ECX, FLAGS;;;--
public _ZeroMemory_ZeroMemory proc near
enter 0,0 push es;; Get source, destination, and count arguments from the stack; Make "count" the number of dwords to move.;
mov edi,dword ptr [bp+4] mov ecx,dword ptr [bp+8] shr ecx,2
;; Load FLAT selectors into DS and ES;
mov ax,KeDataSelector mov es,ax xor eax,eax
;; Zero the the block of data.;assume es:FLAT
;; Zero the dwords; cld rep stos dword ptr [edi]
;; Zero the remaining bytes; mov ecx, dword ptr [bp+8] and ecx, 3 rep stos byte ptr [edi]
assume es:nothing, ds:DGROUP
pop es leave ret
_ZeroMemory endp
;++;; Turn Floppy Drive Motor Off;;--
public _TurnMotorOffDriveControlRegister equ 3f2h ; Floppy control register
_TurnMotorOff proc near
mov dx,DriveControlRegister mov ax,0CH out dx,al ret
_TurnMotorOff endp
;; Note: we do not save and restore the gdt and idt values because they; cannot change while external services are being used by the OS loader.; This is because they MUST remain identity mapped until all mode; switching has ceased.;
public _RealMode_RealMode proc near
;; Switch to real-mode;
sgdt fword ptr [_GDTregister] sidt fword ptr [_IDTregister] push [saveDS] ; push this so we can get to it later mov ax,SuDataSelector mov es,ax mov fs,ax mov gs,ax
mov eax,cr0 and eax, not (ENABLE_PAGING + PROT_MODE) mov cr0,eax
;; flush the pipeline; jmp far ptr herehere:
;; Flush TLB;
; HACKHACK - We don't know where the page directory is, since it was; allocated in the osloader. So we don't want to clear out cr3,; but we DO want to flush the TLB....; mov eax,cr3
nop ; Fill - Ensure 13 non-page split nop ; accesses before CR3 load nop ; (P6 errata #11 stepping B0) nop
mov cr3,eax;; switch to real mode addressing;; N. B. We need to do a far jump rather than a retf, because a retf will not; reset the access rights to CS properly.; db 0EAh ; JMP FAR PTR dw offset _TEXT:rmode ; 2000:rmode dw 02000hrmode: pop ax mov ds,ax mov ss,ax;; Stamp video pointers for real-mode use; mov si,offset _ScreenStart mov word ptr [si+2],0b800h mov si,offset _vp mov word ptr [si+2],0b800h;; re-enable interrups; lidt fword ptr [_IDTregisterZero]
;; Re-enable interrupts;
sti ret
_RealMode endp
;** _TransferToLoader - transfer control the the OS loader;;; Arguments:;; None;; Returns:;; Does not return;;**
public _TransferToLoader_TransferToLoader proc near
; generates a double fault for debug purposes; mov sp,0; push 0
mov ebx,dword ptr [esp+2] ; get entrypoint arg xor eax,eax mov ax,[saveDS]
;; Setup OS loader's stack. Compute FLAT model esp to id map to; original stack.; mov cx,KeDataSelector mov ss,cx mov esp,LOADER_STACK ;; Load ds and es with kernel's data selectors;
mov ds,cx mov es,cx
;; Setup pointer to file system and boot context records;; Make a linear pointer to the Boot Context Record
shl eax,4 xor ecx,ecx mov cx,offset _BootRecord add eax,ecx push eax
push 1010h ; dummy return address. push 1010h ; dummy return address.
;; Push 48bit address of loader entry-point; db OVERRIDE push KeCodeSelector push ebx
;; Pass control to the OS loader; db OVERRIDE retf
_TransferToLoader endp
;++; Description:;; Gets memory block sizes for memory from zero to one meg and; from one meg to 64 meg. We do this by calling int 12h; (get conventional memory size) and int 15h function 88h (get; extended memory size).;; Arguments:;; None;; Returns:;; USHORT - Size of usable memory (in pages);;--
public _IsaConstructMemoryDescriptorsBmlTotal equ [bp-4]Func88Result equ [bp-6]_IsaConstructMemoryDescriptors proc near push bp ; save ebp mov bp, sp sub sp, 6;; Initialize the MemoryList to start with a zero entry. (end-of-list); les si, dword ptr _MemoryDescriptorList xor eax,eax mov es:[si].BlockSize,eax mov es:[si].BlockBase,eax
;; Get conventional (below one meg) memory size; push es push si int 12h movzx eax,ax;; EAX is the number of 1k blocks, which we need to convert to the; number of bytes.; shl eax,10
push eax shr eax, 12 mov BmlTotal, eax xor eax,eax push eax call _InsertDescriptor add sp,8
;; Get extended memory size and fill-in the second descriptor;
mov ah,88h
int 15h
mov Func88Result,ax and eax,0ffffh;; EAX is the number of 1k blocks, which we need to convert to the; number of bytes.; shl eax,10 push eax shr eax,12 add BmlTotal, ax mov eax,0100000h push eax call _InsertDescriptor add sp,8
;; Try function E801, see if that is supported on this machine; mov ax,0E801h int 15h jc short Isa50
cmp ax,Func88Result ; Is extended memory same as 88? je short Isa40 ; Yes, go add the rest
cmp ax, (16-1) * 1024 ; Is extended memory exactly 16MB? jne short Isa50 ; No, conflict between 88 & E801
Isa40:;; Function looks like it worked;; AX = extended memory < 16M in 1k blocks; BX = extended memory > 16M in 64k blocks; and ebx,0ffffh jz short Isa50
shl ebx,16 ; ebx = memory > 16M in bytes (via E801) add ebx, 16*1024*1024 ; ebx = end of memory in bytes (via E801)
mov ax, Func88Result and eax,0ffffh shl eax, 10 ; eax = memory > 1M in bytes (via 88) add eax, 1*1024*1024 ; eax = end of memory in bytes (via 88)
sub ebx, eax ; ebx = memory above eax jbe short Isa50 ; if ebx <= eax, done
push ebx shr ebx,12 add BmlTotal, bx push eax call _InsertDescriptor add sp,8 and eax,0ffffh
Isa50: pop si pop es mov eax, BmlTotal mov sp, bp pop bp ret
_IsaConstructMemoryDescriptors endp
;++;; BOOLEAN; Int15E820 (; E820Frame *Frame; );;;; Description:;; Gets address range descriptor by calling int 15 function E820h.;; Arguments:;; Returns:;; BOOLEAN - failed or succeed.;;--
cmdpFrame equ [bp + 6]public _Int15E820_Int15E820 proc near
push ebp mov bp, sp mov bp, cmdpFrame ; (bp) = Frame push es push edi push esi push ebx
push ss pop es
mov ebx, [bp].Key mov ecx, [bp].DescSize lea di, [bp].BaseAddrLow mov eax, 0E820h mov edx, 'SMAP' ; (edx) = signature
INT 15h
mov [bp].Key, ebx ; update callers ebx mov [bp].DescSize, ecx ; update callers size
sbb ecx, ecx ; ecx = -1 if carry, else 0 sub eax, 'SMAP' ; eax = 0 if signature matched or ecx, eax mov [bp].ErrorFlag, ecx ; return 0 or non-zero
pop ebx pop esi pop edi pop es pop ebp ret
_Int15E820 endp
_TEXT ends
end Start
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