Parts

The 717260 patch consist of three parts:

A ROM Extension (REx) patch as an embedded installer package
A ROM patch as an embedded installer package
A patch installer

The parts are combined into one Newton installer package. The patch installer is triggering the installation of the first two embedded packages.

Files

The files in the package can be split into four groups. The patch packages are constructed out of NSOF stream objects, which in turn are either extracted from the original patch verbatim, or generated by the Newton C++ tools by linking compiled code together.

Generic and common files

include/Bytecode.a: Assember macros to generate NewtonScript bytecode
include/package.a: Macros to control package attributes
include/page.a: Macros for MMU page mapping
include/project.a: Definitions for the patch areas
include/sound.a: Not used
include/stream.a: Macros to generate NSOF streams
Makefile: The MPW makefile which controls compilation of the patche code
common.txt: Common definition for the NTK projects
RegisterPatchOriginal.stream: NSOF stream containing the original binary code for the RegisterPatch function. This stream is included in the REx and ROM patch packages verbatim.

REx Patch

The REx patch part patches the ROM extension found at address 0x01e00000.

RExStrmHead.s: Preamble for the REx patch
RExMMU.s: MMU remapping
RExPatch.s: Actual patch data
RExPatch.txt: Text file with the install script and other scripts for the REx patch NTK project
RExPatch: NTK project file used to generate the REx patch package

ROM Patch

The ROM patch part patches the jump tables starting at 0x01a00000.

ROMStrmHead.s: Preable for the ROM patch NSOF stream
ROMMMU.s: MMU page mappings for the ROM patch
Patch1.s to Patch6.s: Actual patch data
ROMPatch.txt: Install script and other scripts for the ROM patch NTK package
ROMPatch: NTK project file used to generate the ROM patch package

Patch Installer

PatchMungerOriginal.stream: Original NSOF stream containing the binary code for installing patch packages
TestPatch.txt: Install and other scripts for the overall patch package
TestPatch: NTK project file for the overall patch package

Memory Layout

The ROM and REx patches are combined into sequential areas. This is the layout of the ROM patch:

% Physical Address % Virtual Address % Source File % Section %
%------------------%-----------------%-------------%---------%
% 0x00000000         %                   % ROMMMU.s      % MMU patch table, 8192 bytes of patch entries to patch 2048 MMU pages %
% 0x00002000         % 0x01d80000        % Patch1.s      %           %
% 0x00003000         % 0x01ae0000        % Patch2.s      %           %
% 0x00004000         % 0x01b40000        % Patch3.s      %           %
% 0x00005000         % 0x01a8c000        % Patch4.s      %           %
% 0x00006000         % 0x01bac000        % Patch5.s      %           %
% 0x00007000         % 0x01c11000        % Patch6.s      %           %

Patch Example

Below is an example of how the TClassOneModem::PrepareCommand is patched. The function implementation is located at address 0x0006399c in the MP2x00 US ROM, and the jumptable entry is at address 0x01a16b3c. Patching the function is achieved by letting the jump table entry point to the patched function.

The ROMMMU.s file contains the first step for this, it maps the page starting at 0x01A16000 to RAM:

; patches of 0x2000
	DontLoadPages 22	; 0x01A00000 - 0x01A15000
	LoadPage 2		; 0x01A16000 needs to be patched
	DontLoadPages 9		; 0x01A17000 - 0x01A1F000

The next step is in Patch1.s, it contains the new page for address 0x01A16000:

L01D80B00
reORG	SETA	{PC} - 0x1A16B00
...
	B	0x001B9AA8 + reORG
	B	0x01B40C5C + reORG ; patch from 0x0006399C, address of the original function
	B	0x001E0F68 + reORG
...

And the final part is in Patch6.s, where the new code for the TClassOneModem::PrepareCommand function is located at address 0x01B40C5C:

L01B40C3C
	STMFD	sp!,{R0,LR}
...
	STMFD	sp!,{R0,R1,LR}
	BL	0x0006399C ; call to the original function, new code follows
	LDMFD	sp!,{R1,R2,LR}
	TEQ	R2,#15
	MOVNE	PC,LR
	LDR	R2,[R1,#1932]
	ADD	R2,R2,#0x000007D0
	STR	R2,[R1,#1932]
	MOV	PC,LR

Compiling the Patch

Prerequisites are MPW, the Newton C++ tools and NTK. The steps to recreate the package are:

Download and extract the patch
Start MPW and set the current directory to the location of the patch
Use the make command to compile the ROMPatch and RExPatch targets:
- Make ROMPatch
- Make RExPatch
Launch NTK
Open the RExPatch project and create the RExPatch package
Open the ROMPatch project and create the ROMPatch package
Open the TestPatch project and create the TestPatch package

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