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List:       openocd-development
Subject:    Re: [OpenOCD-devel] OpenOCD Aarch64 support
From:       Matthias Welwarsky <matthias () welwarsky ! de>
Date:       2016-10-25 20:33:46
Message-ID: 4235115.EId5DXVgvs () linux-feyn ! site
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On Thursday 08 September 2016 11:14:50 Matthias Welwarsky wrote: 
> Let me fill you in on my current state:

So, the current current state can be found here: 

http://openocd.zylin.com/3832 (checkout to get the full branch)

It's actually quite usable, but not yet fully functional.

What I know to be working:

- halt, step, resume via telnet console
- Aarch64 and Aarch32 debugging with gdb, even with multi-arch support present 
in recent gdb versions (I tried 7.11)
- hardware breakpoints in aarch64 and aarch32 states
- software breakpoints in aarch64 state
- SMP support
- gdb single stepping, if you add http://openocd.zylin.com/3833
- virt2phys (using AT instructions)

What still needs work:

- aarch32 soft breakpoints, needs to use the correct T32 "halt" opcode and 
cache management must be extended to work in aarch32 state, too
- virt2phys must use correct T32 opcodes in aarch32 state
- mem access with physical addresses _might_ work, but I have not tested it at 
all. I think the handling of the system control register is still broken.
- banked register access in aarch32 state is not implemented. Not an essential 
feature IMHO, means I'm not going to work on it any time soon.
- Modifying the core mode by writing to the CPSR probably doesn't work. Anyway 
modifying registers in gdb is not immediately effective, registers are updated 
only after resume. I might need to change that? I don't know.
- Interrupts are currently uncinditionally disabled when stepping, needs a 
command to change the behaviour.
- the armv8 dpm functions for break- and watchpoint handling are all majorly 
broken.
- cache handling functions need to be ported from cortex_a
- memory access optimizations. Currently, everything uses MA DTR mode, even 
for transferring a single byte. That is not really efficient. I'm surprised 
that it even works.

That's about it. If you want to help, you're welcome.

BR,
Matthias

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