Can I debug with a debugger PAL/XGL on windows/linux?

[gmmo]

hi, I need to learn more about PAL and XGL but and study these drivers more in depth. Ideally I don't want to just build, run and add logs. I want to debug the driver with a IDE debugger. I want to put breakpoints, view call stacks, etc.

Can it be done? Has anyone done it? Any info you can share, I appreciate.

thank you.

[perlfu]

PAL/XGL is a standard dynamically loaded library (loaded by the Vulkan loader).
If debugging symbols are available, for example by building a debug version of the driver yourself on Linux, then attaching a standard debugger (e.g. gdb) to your Vulkan application will let you set breakpoints and get call stacks within PAL/XGL.

[gmmo]

Have you done it successfully? Can elaborate more since I am a bit new. What do you mean by the Vulkan loader, this is part of the OS? Do I have to build the Vulkan loader too?

[perlfu]

You don't need to build the Vulkan loader, it is part of the Vulkan SDK (from LunarG).
If you fire up a debugger on the vkcube application from the Vulkan SDK then you can break in and see parts of PAL/XGL in the call stack:

$ gdb vkcube
GNU gdb (Ubuntu 12.0.90-0ubuntu1) 12.0.90/
...
(gdb) run
Starting program: /amd/vulkan/1.3.224.1/x86_64/bin/vkcube 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Selected GPU 0: AMD Radeon RX 6800 XT, type: DiscreteGpu
[New Thread 0x7fffe9686640 (LWP 805328)]
^C
Thread 1 "vkcube" received signal SIGINT, Interrupt.
__futex_abstimed_wait_common64 (private=<optimized out>, cancel=true, abstime=0x0, op=393, expected=0, futex_word=0xfc2ff8) at ./nptl/futex-internal.c:57
57	./nptl/futex-internal.c: No such file or directory.
(gdb) bt
#0  __futex_abstimed_wait_common64 (private=<optimized out>, cancel=true, abstime=0x0, op=393, expected=0, futex_word=0xfc2ff8)
    at ./nptl/futex-internal.c:57
#1  __futex_abstimed_wait_common (cancel=true, private=<optimized out>, abstime=0x0, clockid=0, expected=0, futex_word=0xfc2ff8)
    at ./nptl/futex-internal.c:87
#2  __GI___futex_abstimed_wait_cancelable64 (futex_word=futex_word@entry=0xfc2ff8, expected=expected@entry=0, 
    clockid=clockid@entry=0, abstime=abstime@entry=0x0, private=<optimized out>) at ./nptl/futex-internal.c:139
#3  0x00007ffff7a74c5f in do_futex_wait (sem=sem@entry=0xfc2ff8, abstime=0x0, clockid=0) at ./nptl/sem_waitcommon.c:111
#4  0x00007ffff7a74cf8 in __new_sem_wait_slow64 (sem=0xfc2ff8, abstime=0x0, clockid=0) at ./nptl/sem_waitcommon.c:183
#5  0x00007fffeb0746cb in Util::Semaphore::Wait (this=0xfc2ff8, milliseconds=4294967295)
    at /amd/gpuopen/drivers/pal/src/util/lnx/lnxSemaphore.cpp:79
#6  0x00007fffeb544ece in Pal::SwapChain::AcquireNextImage (this=0xfc2de8, acquireInfo=..., pImageIndex=0x7fffffffdea0)
    at /amd/gpuopen/drivers/pal/src/core/swapChain.cpp:167
#7  0x00007fffeb4e01c7 in Pal::Amdgpu::SwapChain::AcquireNextImage (this=0xfc2de8, acquireInfo=..., pImageIndex=0x7fffffffdea0)
    at /amd/gpuopen/drivers/pal/src/core/os/amdgpu/amdgpuSwapChain.cpp:394
#8  0x00007fffeae4f418 in vk::SwapChain::AcquireNextImage (this=0xfc2c90, pAcquireInfo=pAcquireInfo@entry=0x7fffffffcb90, 
    pImageIndex=0x7fffffffdea0) at /amd/gpuopen/drivers/xgl/icd/api/vk_swapchain.cpp:689
#9  0x00007fffeae4f636 in vk::entry::vkAcquireNextImageKHR (device=<optimized out>, swapchain=<optimized out>, 
    timeout=<optimized out>, semaphore=<optimized out>, fence=<optimized out>, pImageIndex=<optimized out>)
    at /amd/gpuopen/drivers/xgl/icd/api/vk_swapchain.cpp:1781
#10 0x0000000000404524 in demo_draw (demo=0x7fffffffd170) at /vulkan-sdk/1.3.224.1/source/Vulkan-Tools/cube/cube.c:1045
#11 demo_run_xcb (demo=0x7fffffffd170) at /vulkan-sdk/1.3.224.1/source/Vulkan-Tools/cube/cube.c:2747
#12 main (argc=<optimized out>, argv=<optimized out>) at /vulkan-sdk/1.3.224.1/source/Vulkan-Tools/cube/cube.c:4316
(gdb)