Skip to content
This repository has been archived by the owner on May 10, 2024. It is now read-only.

Latest commit

 

History

History
32 lines (30 loc) · 2.27 KB

trace-hooks.md

File metadata and controls

32 lines (30 loc) · 2.27 KB
Raw

trace hooks

Container-tracer uses a set of trace hooks to interact with the tracing infrastructure of the Linux kernel. The trace hooks are responsible to configure a tracing session with given context in the kernel and to return a location of a text file, where traces of this session are recorded. Usually, this tracing context is a set of PIDs that will be traced and input arguments, specific to the trace-hook. The trace hooks are located in the trace-hooks directory and are organized into sub-directories. Each sub-directory is responsible for a specific trace sub-system of the Linux kernel. There is at least one executable file in each of these sub-directories, called manager, which manages all trace hooks located in that sub-directory. The manager must accept at least these input arguments:

  • --get-all : Return a list of all user callable trace hooks.
  • --describe : Get a user description of the given trace hook.
  • --clear : Reset to default the trace sub-system of the Linux kernel.
  • --run : Run a trace hook, in blocking mode. In case of an error, an error message must be printed on the standard error output and the hook must return, without starting any trace session. If everything is OK, only the full path to a file where traces are collected must be printed on the standard output, no prints on the standard error. The trace hook blocks this instance of the manager during the trace session. The trace session stops when this instance of manager receives a SIGINT signal.
  • --args : Arguments that will be passed to the trace hook.

These environment variables can be used to set system specific configuration to trace hooks, the manager must read them and apply this configuration:

  • TRACER_PROCFS_PATH: Mount location of the host /proc file system. If not set, the default /proc is used.
  • TRACER_SYSFS_PATH: Mount location of the host /sys file system. If not set, the default /sys is used.

Container-tracer uses manager to auto-discover and run available trace hooks. New types of trace hooks, to a different tracing subsystem, can be added easily by creating a new sub-directory in trace-hooks and implementing manager for them.