Day 9: OpenCL target debugging with gdb-igfx

How to use Intel gdb-igfx to debug Intel GPU.

Everything starts with this article: Getting Started with Debugging with Intel® Parallel Studio XE 2016 [1]. unfortunately, the article is quite old now ("Last updated on August 25, 2015") and not really up-to-date anymore.

No, wait, there is a newer version there [2] for Intel Parallel Studio 2017.

sudo modprobe igfxdcd

igfxdcd: loading out-of-tree module taints kernel.
igfxdcd: module verification failed: signature and/or required key missing - tainting kernel
igfxdcd: warning: this is an untested device ID.
Setting dangerous option enable_hangcheck - tainting kernel
Setting dangerous option enable_cmd_parser - tainting kernel
igfxdcd: Debug Companion Driver for Intel(R) graphics

To work with the Intel® SDK for OpenCL* - Debugger plug-in, the OpenCL* kernel code must exist in a text file separate from the code of the host. Debugging OpenCL* code that only appears in a string embedded in the host application is not supported.

ina@nuc:~/simple_add$ gdbserver-igfx :3333 simple_add
Inferior creation not supported, use the --debug option
Exiting

export GFX_NOTIFY_DEBUGGER=1
export GFX_PROG_OPTIONS="-generateDebugInfo -debug -addKernelID"
export GFX_OFFLOAD_TIMEOUT_FUNC=0
export IGFXDBG_IDE_START_UP_MODE=1

$TARGET_ROOT/bin/gdbserver $@

You can see strange environment variable initialized before starting the gdbserver command:

  • GFX_NOTIFY_DEBUGGER:
  • GFX_PROG_OPTIONS
  • GFX_OFFLOAD_TIMEOUT_FUNC
  • IGFXDBG_IDE_START_UP_MODE