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6opuc/lldb-netcore

By 6opuc

•Updated over 6 years ago

Docker image for netcore coredump debugging

Image
2

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6opuc/lldb-netcore repository overview

⁠lldb-netcore

Docker image with lldb debugger and SOS plugin, compiled from sources with lldb headers. By default loads process coredump from /tmp/coredump, loads SOS plugin and prints current exception, leaving lldb shell open. Image tag matches dotnet runtime version.

⁠How to use

docker run --rm -it -v /stripe/upload/coredump:/tmp/coredump 6opuc/lldb-netcore
  • /stripe/upload/coredump - Path to coredump of crashed process on docker host machine

⁠Usecases

⁠Container crashed
  1. Copy crashed process working directory(coredump is automatically created in crashed process working directory) to temporary directory on host:
docker cp 79686a7aff63:/app /tmp
  • 79686a7aff63 - id of container with crashed process
  • /app - crashed process working directory inside container filesystem
  1. Find crashed process coredump:
ls /tmp/app/core.*

example output:

/tmp/app/core.26939
  1. Open coredump with debugger:
docker run --rm -it -v /tmp/app/core.26939:/tmp/coredump 6opuc/lldb-netcore

example output:

(lldb) target create "/usr/bin/dotnet" --core "/tmp/coredump"
Core file '/tmp/coredump' (x86_64) was loaded.
(lldb) plugin load /coreclr/libsosplugin.so
(lldb) sos PrintException
Exception object: 00007f3fb001ce08
Exception type:   System.NullReferenceException
Message:          Object reference not set to an instance of an object.
InnerException:   <none>
StackTrace (generated):
    SP               IP               Function
    00007FFCE0A312F0 00007F3FD7940481 test.dll!test.Program.Main(System.String[])+0x1
StackTraceString: <none>
HResult: 80004003
(lldb)
  1. Continue exploring coredump in lldb shell:
help
⁠Analyze running container

  1. Get id of docker container(docker ps) you need to analyze. In this example it is "b5063ef5787c"

  2. Run container with createdump utility(it needs sys_admin and sys_ptrace privileges. If your running container already has these privileges you can attach to running container and run createdump utility from there):

docker run --rm -it --cap-add sys_admin --cap-add sys_ptrace --net=container:b5063ef5787c --pid=container:b5063ef5787c -v /tmp:/tmp 6opuc/lldb-netcore /bin/bash
  • b5063ef5787c - id of container you need to analyze
  • /tmp - temporary directory on host, where coredump will be created
  1. Find PID of dotnet process you need to analyze:
ps aux

In this example PID is "7"

  1. Create coredump of dotnet process and exit from container:
createdump -u -f /tmp/coredump 7
exit
  • 7 is dotnet process PID
  1. Open coredump with debugger:
docker run --rm -it -v /tmp/coredump:/tmp/coredump 6opuc/lldb-netcore

example output:

(lldb) target create "/usr/bin/dotnet" --core "/tmp/coredump"
Core file '/tmp/coredump' (x86_64) was loaded.
(lldb) plugin load /coreclr/libsosplugin.so
(lldb) sos PrintException
There is no current managed exception on this thread
(lldb)
  1. Continue exploring coredump in lldb shell:
help

⁠How to build

⁠netcore 2.2.3:
docker build \
	--tag 6opuc/lldb-netcore:2.2.3 \
   	--build-arg BASE_IMAGE=mcr.microsoft.com/dotnet/core/sdk:2.2.105 \
   	--build-arg CORECLR_BRANCH=v2.2.3 \
	.
⁠netcore 2.2.2:
docker build \
	--tag 6opuc/lldb-netcore:2.2.2 \
   	--build-arg BASE_IMAGE=mcr.microsoft.com/dotnet/core/sdk:2.2.104 \
   	--build-arg CORECLR_BRANCH=v2.2.2 \
	.
⁠netcore 2.1.8:
docker build \
	--tag 6opuc/lldb-netcore:2.1.8 \
	--build-arg BASE_IMAGE=mcr.microsoft.com/dotnet/core/sdk:2.1.504 \
   	--build-arg CORECLR_BRANCH=v2.1.8 \
	.
⁠netcore 2.0.3:
docker build \
	--tag 6opuc/lldb-netcore:2.0.3 \
	--build-arg BASE_IMAGE=microsoft/dotnet:2.0.3-sdk \
	--build-arg CORECLR_BRANCH=v2.0.3 \
	.

Tag summary

Content type

Image

Digest

Size

776.8 MB

Last updated

over 6 years ago

docker pull 6opuc/lldb-netcore