Chapter 8 - FAQ.
Q: What is a hit?
A: If a program is accessing the zero-page (also called the low-page) or any
non-available memory, it will create a hit. Basically, a hit is the report
of an illegal memory access.
Hits are never harmless. They are program bugs and must be fixed.
Q: What are Enforcer, Cyberguard and all these MMU tools?
A: They are very hardware specific tools watching for illegal memory access.
Do not use them! The same functionality is already built-in MorphOS and is
Q: What's SegTracker?
A: This tool tracks all code locations. When something is loaded in memory,
address is stored and put in a database. Then MorphOS uses it to display
the name of a crashed module. It's possible to more easily identify where
hits come from: libraries, devices, handlers, etc
SegTracker functionnality is built-in MorphOS and is always active.
Q: MorphOS doesn't seem to detect read-access to address 0. Is it normal?
A: Yes, MorphOS doesn't read-protect zero page; yet. It write-protects it
Q: What is the memtracker?
A: It is a powerfull debug tool built-in MorphOS. It tracks memory allocations
and reports wrong freeing sizes and mismatching pointers.
Activate it by using the MorphOS' EDebugFlags boot argument.
EDebugFlags="permmemtrack" permanently activates memtracker.
EDebugFlags="permmemtrack memtrack" also activates memtracker's output.
When memtracker is used (EDebugFlags="permmemtrack"), it is possible to
disable/enable its output on the fly, using SystemSettings/Debug/MemTrack.
When permmemtrack is not used, memtrack still toggles memtracker on/off but
it won't notice invalid freeing of memory.
Please note the memtracker fills all free memory using the 0xABADCAFE
pattern. It helps to catch uninitialised pointers, or using already free
Q: Why does the system become slower when the memtracker is enabled?
A: The memtracker involves a lot of extra operations during memory allocation
and deallocation. It is a pure debug tool. Only use it when you need to
track a problem or when you want to check your memory management
Q: Objdump is slow when processing big executable files. Is it possible to
speed it up?
A: Yes. It can be restricted to dump only a certain address range around an
Just type "objdump" in a shell and read its argument-options. You are
looking for the --start-address=addr and --stop-address=addr ones.
objdump program -disassemble-all --start-address=10000 --stop-address=20000 >program.dump
Q: Objdump crashed, how is it possible to debug anyway?
A: It seems there is a problem with objdump. You can workaround it by
restricting the dump to a smaller range. See above.
Q: How do I use FindHit?
A: You can't. Please use objdump for now.
Q: I heard about addr2line. Can it be used like FindHit?
A: There is a problem with addr2line and it isn't reliable. But CISC is
working on it. :-)
Q: How can I output my own debug information? I used to use kprintf().
A: You can still use kprintf(). It is in libdebug.a
Q: How do I capture kprintf() output?
A: Use sushi/sashimi or use EDebugFlags="logkprintf" MorphOS boot argument.
boot boot.img EDebugFlags="logkprintf"
Q: I heard about dprintf() but how can I use it?
A: You do not. There is no such a public function. Please use kprintf().
Weird error messages in the log:
Q: Why do I get "PPC Stack Ptr is not between PPCSPLower and PPCSPUpper"
A: It means the PPC stack pointer is out of bound.
Perhaps the program used too much PPC stack and did a stack overflow. Or
the r1 register got trashed (r1 is the PPC stack pointer, as defined by the
This can also happen if a program uses setjmp() or any other function
playing with the stack.
Q: Why do I get "68k Stack Ptr is not between SPLower and SPUpper" messsage?
A: Perhaps the program used too much 68k stack and overflowed it. Or the a7
register got trashed (a7 is the 68k stack pointer).
This can also happen if a program uses a non-standard way to swap the stack.
AmigaE applications are known to do it. Then this is not a bug, of course.
Q: Why do I get "Error: TaskEmulHandle 0x00000000 is not a legal address"?
A: EmulHandle is the 68k emulation's entry-point and its address is stored in
r2. It must always be valid. If it is not; r2 register got trashed.
Q: Why do I see offset referring to "Emulation" or "Module"?
A: If an offset is in "Emulation". It means the static emulator was running
some 68k code and you should look at the 68k part of the debug log.
If an offset is in "Module", it simply means that it is somewhere in the
MorphOS module ROM: exec, dos, intuition, sfs...
Q: MorphOS has a JIT emulator. When 68k code crashed, what should I look for;
PPC or 68k code?
A: 68k code.
But, when Trance is running, the PC register is referring to the start of
the translated code-block. This is probably not exactly the point where the
crash happened but it's the only available reference to it. You might want
to try disabling JIT to get the precise location of the problem.
Q: I have a really complex crash and much more StackFrame would be needed to
track the problem in my code. What is it possible to do?
A: There is a BackTraceDepth argument to choose the amount of displayed
StackFrame. See the documentation in SYS:Docs/PegasosFirmware.txt
boot boot.img BackTraceDepth=10
Q: The system freezes, there is no console window and I can't get the ramdebug
A: It may be possible to get the ramdebug log after a reboot if the firmware
didn't clear the memory. It all depends on your hardware setup.
But the best solution is to use serial debug.
Q: What is the meaning of "FAQ" ?
A: Frequently Asked Questions.
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