Re: git: d6c0538dae8d - main - ddb: Remove SOFTWARE_SSTEP support

On 1/10/22 1:14 PM, Warner Losh wrote:
> On Mon, Jan 10, 2022 at 12:48 PM John Baldwin <jhb@freebsd.org> wrote:
> 
>> On 1/7/22 8:27 AM, Warner Losh wrote:
>>> The branch main has been updated by imp:
>>>
>>> URL:
>> https://cgit.FreeBSD.org/src/commit/?id=d6c0538dae8d138219dfd051994a44c50e741212
>>>
>>> commit d6c0538dae8d138219dfd051994a44c50e741212
>>> Author:     Warner Losh <imp@FreeBSD.org>
>>> AuthorDate: 2022-01-07 16:25:33 +0000
>>> Commit:     Warner Losh <imp@FreeBSD.org>
>>> CommitDate: 2022-01-07 16:25:33 +0000
>>>
>>>       ddb: Remove SOFTWARE_SSTEP support
>>>
>>>       It was needed for mips only, and only kinda sorta worked for mips.
>> It
>>>       can be brought back if we grow another architecture that need it.
>>>
>>>       Sponsored by:           Netflix
>>
>> RISC-V would need it in theory (no hardware single step), but no one has
>> felt the
>> need to implement the backend support for it.  I think 32-bit arm doesn't
>> support
>> hardware single step either (but again, no one has bothered to add the
>> backend
>> support).
>>
> 
> Generally, I agree with these thoughts. I went ahead with the removal
> because I
> knew it would be easy to bring back, even years from now should someone[tm]
> have an implementation for those platforms (though I thought 32-bit arm did
> have
> single step in hardware).
> 
> Should I put it back? Or should we wait until someone shows up with support
> for
> a supported platform?

I think the latter.  I don't know that I've ever used single step in DDB on
any platform myself.  In my experience, using a gdb stub in QEMU or via JTAG
or the like is a much better experience for debugging boot-time initialization.

-- 
John Baldwin