*-----------------------------------------------------------
Title[DiskBootSoft.mc...December 14, 1983  4:14 PM...Taft];
* Pilot "soft" boot -- loads a microcode or germ file designated by
* one of the pointers in the physical volume root page.
*-----------------------------------------------------------

TopLevel;
RBase_ RBase[AEmRegs];
Set[XTask, IP[EMU]];


*-----------------------------------------------------------
DiskBootSoft:
* Enter: BootDataPtr = address of base of block (in first 64K of memory)
*	   into which to load the boot file
*	BTemp2 = Descriptor-relative offset of BootingInfo for file to be booted
*	RBase = AEmRegs
*	MemBase = IOBR
* Real memory has been mapped contiguously at the bottom of virtual memory,
* and IOBR contains zero.
* I/O devices have been initialized and are quiescent.
* Call by: SCall[DiskBootSoft]
* Returns +1: Failed
*	+2: Succeeded; BootDataPtr updated to point to last word loaded +1 (mod 2^16)
* Clobbers T, Q, BTemp0, BTemp1
* Also clobbers memory page 0 by reading the physical volume root page into it.
*-----------------------------------------------------------

Subroutine;
	DMBLink_ Link;
TopLevel;
	T_ (R400)+(31C);		* IOCB at 431 (cursor location, odd)
	IOCB_ Sub[sizeIOCB!, 1]C;
	IOCB_ T, Cnt_ IOCB;
	T_ (Store_ T)+1, DBuf_ 0C, Branch[., Cnt#0&-1]; * Zero out the IOCB
	T_ CSB.cylinder;
	Store_ T, DBuf_ 77777C;		* Don't know where disk is positioned

* Transfer the Descriptor.
* Know all of IOCB is zero at this point, so only set nonzero entries.
* In particular, drive = diskAddress = dataPtr = 0
	T_ (IOCB)+(IOCB.pageCount);
	T_ (Store_ T)+1, DBuf_ 1C;	* One page
	Store_ T, DBuf_ 274C;		* command _ [check, read, read]
	SCall[BootTransfer];		* Transfer the Descriptor
	 PD_ T-T, Branch[DiskSBootRet];	* Failed, Carry_ 1

* Make sure the seal and version are ok
	T_ (Fetch_ Add[Desc.seal!]S)+1;
	Fetch_ T, T_ MD, BTemp0_ HighByte[DescSealValue];
	BTemp0_ (BTemp0) OR (LowByte[DescSealValue]);
	BTemp0_ (BTemp0) XOR T, T_ MD;
	T_ T XOR (DescCurrentVersionValue);
	PD_ (BTemp0) OR T;
	T_ (IOCB)+(IOCB.pageCount), Branch[.+2, ALU=0];
	 PD_ T-T, Branch[DiskSBootRet];	* Bad Descriptor, Carry_ 1

* DiskBootSoft (cont'd)

* Read the label of the first page, since certain things (e.g., file type)
* are not known in advance.
	T_ (Store_ T)+1, DBuf_ 1C;	* count _ 1
	BTemp0_ (Store_ T)+1, DBuf_ 260C; * command _ [check, read, none]

* IOCB.diskAddress _ Descriptor.bootingInfo[bootFileType].diskAddress
	T_ (BTemp2)+(DFID.da);
	BTemp1_ T, Cnt_ 1S, Call[BootBlt]; * Want to move 2 words, actually do 3
	SCall[BootTransfer];		* Read the label
	 PD_ T-T, Branch[DiskSBootRet];	* Failed, Carry_ 1

* Now set up to read the entire boot file into memory
	T_ (IOCB)+(IOCB.pageCount);
	T_ (Store_ T)+1, DBuf_ 77777C;	* Transfer as many pages as exist
	BTemp0_ 100000C;		* incrementDataPtr _ TRUE
	BTemp0_ (BTemp0) OR (254C);	* command _ [check, check, read]
	BTemp0_ (Store_ T)+1, DBuf_ BTemp0;

* IOCB.diskAddress _ Descriptor.bootingInfo[bootFileType].diskAddress
* (must do this again because the address was incremented by the microcode).
	T_ (BTemp2)+(DFID.da);
	BTemp1_ T, Cnt_ 1S, Call[BootBlt]; * Want to move 2 words, actually do 3

* IOCB.dataPtr _ BootDataPtr
	T_ (IOCB)+(IOCB.dataPtr);
	Store_ T, DBuf_ BootDataPtr;

* IOCB.diskLabel.fileID _ Descriptor.bootingInfo[bootFileType].fID;
* IOCB.diskLabel.filePageLo _ Descriptor.bootingInfo[bootFileType].firstPage;
	BTemp0_ T+(Sub[IOCB.diskLabel!, IOCB.dataPtr!]C);
	T_ (BTemp2)+(DFID.fID);
	BTemp1_ T, Cnt_ 4S, Call[BootBlt]; * Move 6 words

* IOCB.diskLabel.bootChainLink _ 0;
	T_ (IOCB)+(Add[IOCB.diskLabel!, Lab.bootChainLink!]C);
	T_ (Store_ T)+1, DBuf_ 0C;
	Store_ T, DBuf_ 0C;
	SCall[BootTransfer];		* Transfer the boot file
	 PD_ T-T, Branch[DiskSBootRet];	* Failed, Carry_ 1
	T_ (IOCB)+(IOCB.dataPtr);
	PD_ Fetch_ T;			* Get updated dataPtr; Carry_ 0

* Carry=0 if completed successfully, 1 if unsuccessfully.
DiskSBootRet:
	Link_ DMBLink, T_ MD;
Subroutine;
	BootDataPtr_ T, Return[Carry'];	* This clobbers BootDataPtr on fail return


*-----------------------------------------------------------
BootBlt:	* Copy memory to and fro
* Enter: BTemp0 = first destination address
*	BTemp1 = first source address
*	Cnt = (# words to transfer)-2
* Exit:	BTemp0 and BTemp1 advanced by number of words transferred
* Clobbers T
*-----------------------------------------------------------
Subroutine;

	BTemp1_ (Fetch_ BTemp1)+1;
	BTemp1_ (Fetch_ BTemp1)+1, T_ MD;
	BTemp0_ (Store_ BTemp0)+1, DBuf_ T, Branch[.-1, Cnt#0&-1];
	BTemp0_ (Store_ BTemp0)+1, DBuf_ MD, Return;