[lldb-dev] Skipping registers when restore register state after a function call

[Pavel Labath via lldb-dev]

Aha, I see. I take it these are some registers which provide the state
of the cpu, but are not modifiable by user code. Presumably the same
crash would happen if the user manually issued a "register write"
command (?)

The fact that the stub crashes after this command sounds like a bug in
the stub for me. However, even if it is fixed to return error, the
register save-restore machinery might get confused by the fact that
the register write failed. Maybe we could try adding a read-only field
to the register info struct to let the machinery know it should not
touch this register?

On 13 July 2017 at 12:26, Tatyana Krasnukha via lldb-dev
<lldb-dev at lists.llvm.org> wrote:
> I'm porting lldb to baremetal ARC target and now I try to call functions from expressions. It works well until ThreadPlanCallFunction tries to restore register state. In that moment my gdb-server crashes because of attempt to write some registers that shouldn't be written.
>
> Thanks,
> Tatyana
>
> -----Original Message-----
> From: Pavel Labath [mailto:labath at google.com]
> Sent: Thursday, 13 July, 2017 2:16 PM
> To: Tatyana Krasnukha <Tatyana.Krasnukha at synopsys.com>
> Cc: lldb-dev at lists.llvm.org
> Subject: Re: [lldb-dev] Skipping registers when restore register state after a function call
>
> I'm not sure there is a good way to do that currently.
>
> However, if you tell us what is the higher level problem you are trying to solve, we may be able to provide an alternative (right now, the only reason I can think of why you would *not* want to save/restore all registers is the orig_rax pseudo-register, for which we do have a solution)
>
> On 13 July 2017 at 12:06, Tatyana Krasnukha via lldb-dev <lldb-dev at lists.llvm.org> wrote:
>> Hi,
>>
>> I need an ability to skip some registers when lldb restores register
>> state after a function call. Didn’t find something like gdb “save-restore”
>> register property. Is there any way to avoid restoring of some
>> registers beside hardcoding its names in
>> GDBRemoteRegisterContext::WriteAllRegisterValues like it is done for
>> arm debugserver?
>>
>>
>>
>> Thanks for any suggestions,
>>
>> Tatyana
>>
>>
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