[lldb-dev] process launch: exec past eLaunchFlagDebug for debugserver local debugging

[Todd Fiala]

Ok looks like I'm not getting ProcessGDBRemote's concept of UnixSignals
correct for Linux on the lldb-launch, llgs-attach mode for local debugging.
 This is causing mismatches in signal numbers --- LinuxSignals differ in
some important ways from the default UnixSignals.


On Fri, Aug 22, 2014 at 3:13 PM, Todd Fiala <tfiala at google.com> wrote:

>
>
>
> On Fri, Aug 22, 2014 at 2:59 PM, Todd Fiala <tfiala at google.com> wrote:
>
>> Hey Greg,
>>
>> Where is the code in lldb that does the final 'resume' when we get the
>> inferior stopped at the entry point with eLaunchFlagDebug?
>>
>> I've got my local Linux debugging working with llgs with a band-aid fix
>> to address the race condition, but I do consistently stop at the entry
>> point to the program (the exec stop for the final exec into the true
>> inferior process).
>>
>> Another symptom I'm seeing (maybe it is related) is that lldb doesn't
>> seem to know what the target is.  IOW, I see this kind of behavior:
>>
>> tfiala at tfiala2:/mnt/ssd/work/macosx.sync/mp-git/build-debug$ bin/lldb --
>> ~/play/loops/loops
>> (lldb) target create "/usr/local/google/home/tfiala/play/loops/loops"
>> Current executable set to
>> '/usr/local/google/home/tfiala/play/loops/loops' (x86_64).
>> (lldb) run
>> Process 20363 launched: '/usr/local/google/home/tfiala/play/loops/loops'
>> (x86_64)
>> Process 20363 stopped
>> * thread #1: tid = 20363, 0x00007f9b806f02d0, name = 'loops', stop reason
>> = exec
>>     frame #0: 0x00007f9b806f02d0
>> -> 0x7f9b806f02d0:  movq   %rsp, %rdi
>>    0x7f9b806f02d3:  callq  0x7f9b806f3a70
>>    0x7f9b806f02d8:  movq   %rax, %r12
>>    0x7f9b806f02db:  movl   0x221b17(%rip), %eax
>>
>> // ^= here you see the behavior where I stop at the final exec (as I'd
>> expect at the private level, but I'd expect lldb to want to continue it at
>> the public level).
>>
>> (lldb) c
>> Process 20363 resuming
>> i = 0
>> i = 1
>> i = 2
>> i = 3
>> i = 4
>> i = 5
>> i = 6
>> i = 7
>> i = 8
>> i = 9
>> Process 20363 exited with status = 0 (0x00000000)
>> (lldb) run
>> error: no file in target, create a debug target using the 'target create'
>> command
>>
>> // ^= Huh?  I should be able to re-run :-)
>>
>> (lldb)
>>
>
> On this part, I think I may not be clearing out everything that needs to
> be cleared out on an exec.  I'm going to trace what debugserver/lldb does
> on MacOSX when an exec is detected to see if I'm missing anything on the
> Linux llgs/lldb side.
>
>
>>
>> --
>> Todd Fiala |  Software Engineer | tfiala at google.com |  650-943-3180
>>
>
>
>
> --
> Todd Fiala | Software Engineer |  tfiala at google.com |  650-943-3180
>



-- 
Todd Fiala | Software Engineer | tfiala at google.com | 650-943-3180
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