Unable to get full user-mode stacktrace while kernel debugging in windbg - windows

Question

I have a virtual Windows 7 x64 machine on a Windows 10 host, and I kernel debug it with windbg 10.0.10586.567. I'm running my own application on it, which I have full source and private symbols for. Whenever I break in and ask for stack traces of the app's threads, the backtrace always stops when one of my application's binaries are "hit."
So for instance, if I break in, switch to the process, and request a stacktrace with !thread [thread address] 1f, I get something like this (note the "early" zero return address at the last line):
fffff880`0534e870 fffff800`026d6992 nt!KiSwapContext+0x7a
fffff880`0534e9b0 fffff800`026d81a2 nt!KiCommitThreadWait+0x1d2
fffff880`0534ea40 fffff800`029c7a2e nt!KeDelayExecutionThread+0x186
fffff880`0534eab0 fffff800`026d08d3 nt!NtDelayExecution+0x59
fffff880`0534eae0 00000000`76e7165a nt!KiSystemServiceCopyEnd+0x13 (TrapFrame # fffff880`0534eae0)
00000000`00276708 000007fe`fcf91203 ntdll!NtDelayExecution+0xa
00000000`00276710 00000001`410e7dd9 KERNELBASE!SleepEx+0xab
00000000`002767b0 00000000`00000000 MyApp!MainMessageLoop+0x4b1 [d:\whatever\path\myapplication.cpp # 3024]
This looks very similar to when you you are missing a binary while debugging a user-mode dump (lack of unwind data) of an x64 process, except in that case the stack trace usually does not stop "this sudden", rather it goes astray at that point, and shows bogus values.
Some extra info/things I tried:
I have the correct symbol paths set up (both the Microsoft symbol server, and a local folder on the host with matching PDBs, even though the latter is not needed for just the stack trace)
I have a binary path set up (.exepath) containing matching binaries on the host (I've made absolutely sure of this; copied the binaries directly from the guest to the host machine)
If I put a breakpoint in one of the app's exported DLL functions, then when the debugger breaks in, I get a one-liner stack trace like this: 0000000000274b40 0000000000000000 MyAppDLL!SomeExportedFunction+0x32 [d:\whatever\path\myapplicationDLL.cpp # 232]
I've tried virtually every combination of commands to get a stacktrace (.process /i, .process /r /p, !process -1 7, .reloads, .reload /users, .reload /f MyApp.exe, !thread [address] 1f, etc.) with no success
Tried with an older version of windbg (6.11.0001.404) as well, same result
Also tried on Windows 8.1 as a guest with the very same binaries, same result
!sym noisy output (irrelevant lines omitted):
0: kd>.process /i [address]
0: kd>g
0: kd>.reload /user
0: kd> !process -1 2
0: kd> !thread [address] 1f
[...]
DBGHELP: d:\symbolcache\MyApp.pdb\76931C5A6C284779AD2F916CA324617E1\MyApp.pdb already cached
DBGHELP: MyApp - private symbols & lines
[...]
lmvm MyApp output:
[...]
Loaded symbol image file: MyApp.exe
Image path: C:\MyApp\MyApp.exe
[...]
Any ideas?

Answer 1

I accidentally stumbled into a linker switch that solves this problem: /DEBUGTYPE with the PDATA argument. If you link your binaries with this switch, unwind information will be copied into your PDBs.
I recompiled/relinked the application in question with /DEBUGTYPE:CV,PDATA (/DEBUGTYPE:CV is the default if /DEBUG is specified, see the documentation), now everything works like a charm, I always get full call stacks.
One strange aspect of this: windbg happily uses unwind data found in the PDBs, but ignores the very same data in the mapped binaries (both on the host machine).

Answer 2

This is not a perfect solution to the problem (or any solution at all, one might say), but I'm providing this provisional answer with a workaround.
You should be able to get the information you want, albeit not so well-formatted using something like dps #rsp L10.
In x86-64 you don't have a parallel of the x86 ebp-chain, but the return addresses are still on the stack. Those will give you the functions in the stack, and the values between them will be the arguments passed to the functions (and saved registers on the stack, etc.). A random example from Google (as I'm not on my Windows machine right now):
0:017> dps #rsp
00000000`1bb0fbb8 00000000`00000020
00000000`1bb0fbc0 00000000`00000000
00000000`1bb0fbc8 00000000`008bc6c6 Dolphin!ReadDataFromFifoOnCPU+0xb6 [d:\sources\comex\source\core\videocommon\fifo.cpp # 245]
00000000`1bb0fbd0 00000000`1ba0ffeb
00000000`1bb0fbd8 00000000`00000020
00000000`1bb0fbe0 00000000`00000020
00000000`1bb0fbe8 00000000`00000800
00000000`1bb0fbf0 00000000`1ba0ffeb
00000000`1bb0fbf8 00000000`008c2ff5 Dolphin!InterpretDisplayListPreprocess+0x45 [d:\sources\comex\source\core\videocommon\opcodedecoding.cpp # 87]
00000000`1bb0fc00 00000000`00000000
00000000`1bb0fc08 00000000`008bc041 Dolphin!RunGpu+0x81 [d:\sources\comex\source\core\videocommon\fifo.cpp # 389]
00000000`1bb0fc10 00000000`8064cbc0
00000000`1bb0fc18 00000000`1bb0fcc0
00000000`1bb0fc20 00000000`00000000
00000000`1bb0fc28 00000000`008c2dda Dolphin!OpcodeDecoder_Preprocess+0x14a [d:\sources\comex\source\core\videocommon\opcodedecoding.cpp # 326]
00000000`1bb0fc30 00000000`8064cbe0
Given that you have symbols, the return addresses are easily distinguishable.

Answer 3

The unwind data is lazy loaded for user mode modules, so it's not going to be mapped unless someone needs it. Unfortunately the kernel debugger doesn't force the information to be present for user images, so sometimes you get this behavior. You can see if the data is mapped or not by dumping the PE header (!dh) and checking the state of the Exception Directory (!pte imagename+offset).
Given that you own the app, try forcing the information to be resident by doing a stack walk NOP somewhere in your app:
PVOID stack[2];
(VOID)CaptureStackBackTrace(0, 2, (PVOID*)&stack, NULL);
That doesn't guarantee the entire directory will be present, but usually good enough.