[lldb-dev] SB API is not working properly with OSPython plugin

[Alexander Polyakov via lldb-dev]

Sure, could you describe in more detail which example may help you?

чт, 14 февр. 2019 г. в 22:36, Jim Ingham <jingham at apple.com>:

> That’s a little complicated…
>
> lldb has two levels of stop state - private stops and public stops.  When
> the process gets notification from the underlying process plugin that the
> process stopped, it raises a private stop event.  That gets handled by the
> ShouldStop mechanism on the private state thread in lldb, and then if the
> stop is judged interesting to the user, it gets rebroadcast as a public
> stop.
>
> For instance, when you issue a “step” command, lldb will stop and start
> the process multiple times as it walks through the source line.  But only
> the last of those stops are relevant to the user of LLDB, so all the other
> ones exist only as private stops.
>
> The SB API’s for the most part should only consider a “publicly stopped”
> process accessible.  After all, you wouldn’t want some API to succeed
> sometimes if you happen to catch it in the middle of a private stop.
>
> But the OperatingSystem plugin needs to get called right after a private
> stop, so it can provide threads for the ShouldStop mechanism.  We should
> really have some formal mechanism whereby things like the OS plugin can
> request elevated rights in the SB API’s, so that they can run at private
> stop time.  IIRC, we instead have a hack where SB API calls that run on the
> private state thread are blanket allowed to run at private stop.  The xnu
> Operating System plugin successfully gets global values to look up its
> threads.  So I’m not sure why that isn’t working for you.
>
> Can you cook up a simple example showing the failure and I’ll have a look?
>
> Jim
>
>
> On Feb 14, 2019, at 11:10 AM, Alexander Polyakov <polyakov.alx at gmail.com>
> wrote:
>
> It is, the error is: *error: error: process must be stopped.*
>
> I thought that the plugin (get_thread_info in my case) is invoked when the
> process is already stopped, but it's not. Is it ok?
>
> On Thu, Feb 14, 2019 at 9:53 PM Jim Ingham <jingham at apple.com> wrote:
>
>> All SBValues have an error in them (SBValue.GetError).  Does that say
>> anything interesting?
>>
>> Jim
>>
>>
>>
>>
>> On Feb 14, 2019, at 10:08 AM, Alexander Polyakov via lldb-dev <
>> lldb-dev at lists.llvm.org> wrote:
>>
>> Hi lldb-dev,
>>
>> I work on a custom implementation of OperatingSystem plugin using Python
>> and SB API. I’m trying to fetch information about some variables from the
>> target into the plugin, to do that I’m using the following Python code:
>> ready_tasks = self._target.FindGlobalVariables(‘pxReadyTasksLists’,
>> 1).GetValueAtIndex(0)
>>
>>
>> When I do `print(ready_tasks)` I get:
>> No value
>>
>>
>> At the same time, doing the same actions inside lldb embedded interpreter
>> follows to:
>> `
>> print(lldb.target.FindGlobalVariables('pxReadyTasksLists',1).GetValueAtIndex(0))`
>>
>>
>> (List_t [5]) pxReadyTasksLists = {
>>   [0] = {
>>     uxNumberOfItems = 0
>>     pxIndex = 0x00000000
>>     xListEnd = {
>>       xItemValue = 0
>>       pxNext = 0x00000000
>>       pxPrevious = 0x00000000
>>     }
>>   }
>> …
>>
>>
>> Does anybody know what may cause such a behavior?
>>
>> --
>> Alexander
>> _______________________________________________
>> lldb-dev mailing list
>> lldb-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>>
>>
>>
>
> --
> Alexander
>
>
> --
Alexander
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