----- Original Message -----
> On Fri 2019-06-21 11:45 -0400, Dave Anderson wrote:
> >
> >
> > ----- Original Message -----
> > > Changes since v1:
> > >
> > > - Update 'dis' help page
> > > - Resolve patch fuzz
> > >
> > >
> > > The purpose of this patch is to add support for a count value in reverse
> > > or forward mode, during disassembly:
> > >
> > > 'dis [-r|-f] [symbol|address] [count]'
> > >
> > > For example:
> > >
> > > crash> dis -f list_del+0x16 4
> > > 0xffffffff812b3346 <list_del+22>: jne 0xffffffff812b3381
> > > <list_del+81>
> > > 0xffffffff812b3348 <list_del+24>: mov (%rbx),%rax
> > > 0xffffffff812b334b <list_del+27>: mov 0x8(%rax),%r8
> > > 0xffffffff812b334f <list_del+31>: cmp %r8,%rbx
> > >
> > > crash> dis -r list_del+0x16 4
> > > 0xffffffff812b333c <list_del+12>: mov 0x8(%rdi),%rax
> > > 0xffffffff812b3340 <list_del+16>: mov (%rax),%r8
> > > 0xffffffff812b3343 <list_del+19>: cmp %r8,%rdi
> > > 0xffffffff812b3346 <list_del+22>: jne 0xffffffff812b3381
> > > <list_del+81>
> [ ... ]
>
> Hi Dave,
>
> > To be honest, it's not clear how that can be addressed, because any patches
> > to printcmd.c must be applicable to the non-ppc64le and the ppc64le
> > versions
> > of the file.
>
> Unfortunately, I believe this is the underlying issue.
> I did not compile test under ppc64le.
>
> > So let's take a step back, and consider the risk/reward of this quite intrusive
> > patchset to such a crucial gdb file.
>
> In my opinion and if I understand correctly, the original GDB commit
> bb556f1facb ("Add negative repeat count to 'x' command") is rather
> self-contained and should not cause an issue. I was particularly careful in
> this regard. Moving forward, I could strip out all but absolutely necessary
> changes from the original GDB commit, to support this feature.
>
> > First, "dis -f <address> <count>" is pretty much meaningless. In order
> > to accomplish that, just don't use the "-f" argument!
>
> I agree - this is superficial; count in forward mode was added since
> reverse mode also accepts a count.
>
> > Secondly, for "dis -r <address> count", you could simply run "dis -r
> > <address> | tail -4".
> > For that matter, is it really all that onerous to see the fully
> > disassembled function
> > up to the target address?
>
> Personally, I would prefer to avoid using an external command in this
> particular case. Especially since the GDB command examine supports a
> positive or negative (i.e. in GDB release 7.12 and above) count.
>
> > And again, even if you wanted to support it, it also seems like it could be accomplished
> > within the cmd_dis() function, given that the full output is pre-gathered into a tmpfile
> > prior to being displayed.
>
> We can indeed but it would be easier to utilise GDB for this as explained
> above.
>
> If you don't mind another iteration, I'll attempt to address the above
> build issues. Please let me know your thoughts.
I can't stop you from trying, but I have to say that you're not calming
my nerves, because:
(1) I don't care whether gdb-7.12 has that capability.
(2) If it is at all possible to refrain from tinkering with
the temperamental beast gdb, I would always rather do so.
In the interest of simplicity and maintainability, it just seems that
here in cmd_dis():
2019 gdb_pass_through(buf5, NULL, GNU_RETURN_ON_ERROR);
2020
2021 if (req->flags & GNU_COMMAND_FAILED) {
2022 close_tmpfile();
2023 error(FATAL, dis_err, req->addr);
2024 }
2025
2026 rewind(pc->tmpfile);
2027 while (fgets(buf2, BUFSIZE, pc->tmpfile)) {
at line 2025, you could do something like:
if (count_entered and reverse)
set_reverse_offset(req->count);
else
rewind(pc->tmpfile)
Your choice...
Dave
>
>
> Kind regards,
>
> --
> Aaron Tomlin
>
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