[lldb-dev] Problem unwinding from inside of a CRT function

Tue Jan 20 15:03:18 PST 2015

Not we also list all of the process' threads using the "threads:a,b,c,d;" format in each stop reply. It doesn't take up much space and it also stops your from having to make two packets round trip calls using qfThreadInfo and qsThreadInfo.

Greg

> On Jan 20, 2015, at 2:59 PM, Greg Clayton <gclayton at apple.com> wrote:
> 
> See if you can expedite all of your GPR registers in your stop reply and qThreadStopInfo responses. We are typically slowed down by packet send/receive, so we try to minimize them by always including all registers in the stop reply and qThreadStopInfo. Otherwise we will send a p packet to read each register we need.
> 
> Below is an example from debugging TextEdit.app on MacOSX:
> 
> <   5> send packet: $c#63
> send packet: \x03
> < 587> read packet: $T11thread:3fe26e;qaddr:7fff77e5c480;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:0540001000000000;01:ffffffff00000000;02:28e1bf5fff7f0000;03:0000000000000000;04:90e2bf5fff7f0000;05:0608000700000000;06:70e1bf5fff7f0000;07:28e1bf5fff7f0000;08:0b1b000000000000;09:ffffffff00000000;0a:000c000000000000;0b:0602000000000000;0c:000c000000000000;0d:0000000000000000;0e:90e2bf5fff7f0000;0f:0b1b000000000000;10:2e351a88ff7f0000;11:0602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;metype:5;mecount:2;medata:10003;medata:11;#00
> SendInterrupt () - sent interrupt, private state stopped
> <  25> send packet: $qThreadStopInfo3fe292#96
> < 542> read packet: $T00thread:3fe292;qaddr:10009c180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7101000200000000;01:0000000000000000;02:b8b5090001000000;03:0000000000000000;04:0300000000000000;05:0000000000000000;06:40b6090001000000;07:b8b5090001000000;08:0100000000000000;09:0000000000000000;0a:d0b5090001000000;0b:4602000000000000;0c:5892398bff7f0000;0d:c04e2077ff7f0000;0e:d0b5090001000000;0f:00b6090001000000;10:2e921a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe293#97
> < 542> read packet: $T00thread:3fe293;qaddr:100581180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7001000200000000;01:0000010000000000;02:180f580001000000;03:0000000000000000;04:0400000000000000;05:0000000000000000;06:500f580001000000;07:180f580001000000;08:0000000000000000;09:0000000000000000;0a:0000000000000000;0b:4602000000000000;0c:ff10008000000000;0d:0316000000000000;0e:0010580001000000;0f:1900000000000000;10:46891a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe294#98
> < 542> read packet: $T00thread:3fe294;qaddr:100604180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:0500000200000000;01:f82d600001000000;02:f81c600001000000;03:d8490a0000000000;04:d8498a0901000000;05:0480000000000000;06:d022600001000000;07:f81c600001000000;08:0900000000000000;09:2006000000000000;0a:d8498a0901000000;0b:4602000000000000;0c:0000000000000000;0d:0000000000000000;0e:2800000000000000;0f:2026600001000000;10:c67f1a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe2a3#bf
> < 542> read packet: $T00thread:3fe2a3;qaddr:100687180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7001000200000000;01:0000000000000000;02:186f680001000000;03:0000000000000000;04:0400000000000000;05:0000000000000000;06:506f680001000000;07:186f680001000000;08:ff1000a000000000;09:0000000000000000;0a:0000000000000000;0b:4602000000000000;0c:ff08000000000000;0d:0717000000000000;0e:0070680001000000;0f:1500000000000000;10:46891a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe2b4#c1
> < 542> read packet: $T00thread:3fe2b4;qaddr:1056f5180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7001000200000000;01:0000010000000000;02:184f6f0501000000;03:0000000000000000;04:0400000000000000;05:0000000000000000;06:504f6f0501000000;07:184f6f0501000000;08:0200000000000000;09:0000200001000000;0a:0000000000000000;0b:4602000000000000;0c:ff08008000000000;0d:1333000000000000;0e:00506f0501000000;0f:1500000000000000;10:46891a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe2c3#c1
> < 542> read packet: $T00thread:3fe2c3;qaddr:107e81180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7001000200000000;01:0000010000000000;02:180fe80701000000;03:0000000000000000;04:0400000000000000;05:0000000000000000;06:500fe80701000000;07:180fe80701000000;08:de182f88ff7f0000;09:0000300001000000;0a:0000000000000000;0b:4602000000000000;0c:ff20008000000000;0d:0b72000000000000;0e:0010e80701000000;0f:2100000000000000;10:46891a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe2d2#c1
> < 542> read packet: $T00thread:3fe2d2;qaddr:109e81180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7001000200000000;01:0000010000000000;02:180fe80901000000;03:0000000000000000;04:0400000000000000;05:0000000000000000;06:500fe80901000000;07:180fe80901000000;08:0100000000000000;09:0000000000000000;0a:0000000000000000;0b:4602000000000000;0c:ff08008000000000;0d:1b50000000000000;0e:0010e80901000000;0f:1500000000000000;10:46891a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe2f3#c4
> < 542> read packet: $T00thread:3fe2f3;qaddr:109f84180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7001000200000000;01:0000000000000000;02:183ff80901000000;03:0000000000000000;04:0400000000000000;05:0000000000000000;06:503ff80901000000;07:183ff80901000000;08:ff1000a000000000;09:0000000000000000;0a:0000000000000000;0b:4602000000000000;0c:ff08000000000000;0d:0380000000000000;0e:0040f80901000000;0f:1500000000000000;10:46891a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe56a#c5
> < 542> read packet: $T00thread:3fe56a;qaddr:10a703180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:7001000200000000;01:0000000000000000;02:182f700a01000000;03:0000000000000000;04:0400000000000000;05:0000000000000000;06:502f700a01000000;07:182f700a01000000;08:1b00000000000000;09:0000400001000000;0a:0000000000000000;0b:4602000000000000;0c:ff08000000000000;0d:2f97000000000000;0e:0030700a01000000;0f:1500000000000000;10:46891a88ff7f0000;11:4602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> <  25> send packet: $qThreadStopInfo3fe56d#c8
> < 542> read packet: $T00thread:3fe56d;qaddr:10a7a3180;threads:3fe26e,3fe292,3fe293,3fe294,3fe2a3,3fe2b4,3fe2c3,3fe2d2,3fe2f3,3fe56a,3fe56d;00:1f00000100000000;01:ffffffff00000000;02:481f7a0a01000000;03:0000000000000000;04:b0207a0a01000000;05:0608000700000000;06:901f7a0a01000000;07:481f7a0a01000000;08:039d000000000000;09:ffffffff00000000;0a:000c000000000000;0b:0602000000000000;0c:000c000000000000;0d:0000000000000000;0e:b0207a0a01000000;0f:039d000000000000;10:2e351a88ff7f0000;11:0602000000000000;12:0700000000000000;13:0000000000000000;14:0000000000000000;#00
> 
> 
> Above you will see "XX:YYYYYYYYYYYY" where XX are two hex digits for the register number followed by a : and the register bytes. Note these register bytes are in native endian format, not big endian.
> 
> 
> 
>> On Jan 20, 2015, at 2:02 PM, Ted Woodward <ted.woodward at codeaurora.org> wrote:
>> 
>> "The initial stop packet gives us enough registers to know what the current
>> stack frame is."
>> 
>> Which registers would you suggest I have my simulator return in the stop
>> packet?
>> 
>> --
>> Qualcomm Innovation Center, Inc.
>> The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
>> Linux Foundation Collaborative Project
>> 
>> -----Original Message-----
>> From: lldb-dev-bounces at cs.uiuc.edu [mailto:lldb-dev-bounces at cs.uiuc.edu] On
>> Behalf Of Jason Molenda
>> Sent: Tuesday, January 20, 2015 3:16 PM
>> To: Jim Ingham
>> Cc: lldb-dev at cs.uiuc.edu
>> Subject: Re: [lldb-dev] Problem unwinding from inside of a CRT function
>> 
>> 
>>> On Jan 20, 2015, at 1:06 PM, jingham at apple.com wrote:
>>> 
>>> 
>>>> On Jan 20, 2015, at 12:31 PM, Zachary Turner <zturner at google.com> wrote:
>>>> 
>>>> In practice how slow is this for stepping over very lengthy calls?  It
>> sounds like LLDB still generates a call stack at every branch point, which
>> while certainly faster than generating one at every instruction, still seems
>> like it has the potential to be very slow.  
>>> 
>>> At most, lldb only needs to get the current frame & its parent frame to
>> run its stepping algorithm.  It won't generate a full stack frame unless you
>> ask it to.  Getting two frames should be pretty quick.
>> 
>> Specifically -- it will take three packets.  The initial stop packet gives
>> us enough registers to know what the current stack frame is.  lldb will make
>> one memory read of the stack memory, which gives it enough to reconstruct
>> the caller stack frame.  T packet, memory read, memory read result.  Then
>> lldb knows whether to continue stepping, set a breakpoint & resume, or stop
>> stepping.
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