C development and patching for P01/P59

[bubba2533]

Yeah, now I just have to figure out the correct gcc commands to get a asm file compiled.

[antus]

start with the pcmhammer kernel in the pcmhammer repo, get that building then replace the kernel code with your code

https://github.com/LegacyNsfw/PcmHacks/ ... op/Kernels

[Gampy]

Actually, for assembly the PcmHacks/kernels build system would need a little twisting ...

Try this ...
Build.cmd - Slightly twisted for Assembly
Clean.cmd - For keeping tidy
kernel.S - Empty source
kernel.ld - Linker script

AssemblyKernelBuildSystem.zip

(2.13 KiB) Downloaded 110 times

You know me, I'll answer any questions I can.

[bubba2533]

Awesome thanks! That's a great starting point.

[bubba2533]

Well I still can't figure out how to create a label that allows me to easily reference addresses.

I've found documentation that shows how to do it but it doesn't want to compile.

I have a simple function I made to test with:

Code: Select all

MAPUpdate:
	lsr #1,%d3;
	move %d3, (0xFFFFAEEC).w;
	nop;
	nop;
	bra Test;
	nop;
Test:
	nop;
	rts;

I've tried to put this at the beginning at it won't work even though multiple sources have it formatted in this way.

Code: Select all

MAP EQU 0xFFFFAEEC;

MAPUpdate:
	lsr #1,%d3;
	move %d3, (MAP).w;
	nop;
	nop;
	bra Test;
	nop;
Test:
	nop;
	rts;

The branch label works which is great because I've previously had to calculate all the branch values which is really annoying and time consuming.

[Gampy]

Code: Select all

.equ MAP, 0xFFFFAEEC

Edit: Also, loose the semi-colons.

[bubba2533]

Sweet!

Yeah I did that already. Seems to work either way.

[NSFW]

I still think we can find some compiler switches to make C into usable asm, but I'll admit I haven't tried with th M68k compiler. I got reasonable good code from a different Gnu compiler that I used with Subaru though.

For existing addresses in memory I did this:

Code: Select all

#define pRPM                      ((float*)0xFFFF51F8)
#define pSpeed                    ((float*)0xFFFF51E8)
#define pFlagsRevLimit_0x80       ((char*) 0xFFFF5A40)
#define pCruiseFlagsA             ((char*) 0xFFFF4D65)
#define pLeftTgvVoltage           ((float*)0xFFFF2D2C)
#define pThrottlePedal            ((float*)0xFFFF5134)

And then wrote code like this:

Code: Select all

	// Check the clutch switch
	if (((*pCruiseFlagsA & 0x80) == 0) ||
		(pRamVariables->RevMatchState == RevMatchCalibration))
	{
		// Normal rev limiter thresholds.
		fuelCut = RedlineCut;
		fuelResume = RedlineResume;
	}
	else
	{
		if (*pSpeed > FlatFootShiftSpeedThreshold)
		{
			if (*pThrottlePedal > 90.0f)
			{

For the P01 / P59, everything is done with integer math, so instead of float you'd have something like:
#define pThrottlePedal ((uint16_t*)0xFFnnnnnn)

For variables that I created in memory, I defined a RamVariables struct, and did this:

Code: Select all

#define pRamVariables             ((RamVariables*) 0xFFFFA000)

And...

Code: Select all

pRamVariables->VariableName = foo;
foo = pRamVariables->OtherVariableName;

[bubba2533]

Is there any reasonable documentation for the compiler? I was having a really hard time finding anything.

I found this: https://ftp.gnu.org/old-gnu/Manuals/gas ... /as_7.html

Edit: I found this page helpful for more syntax questions... https://ftp.gnu.org/old-gnu/Manuals/gas ... tml#SEC214

[Gampy]

Command line help is the best, then general GNU docs is all I know of, I'm sure there is others ...