Systrack

See mebeim/linux-syscalls for live syscall tables powered by Systrack.

Systrack is a tool to analyze Linux kernel images (vmlinux) and extract information about implemented syscalls. Given a vmlinux image, Systrack can extract syscall numbers, names, symbol names, definition locations within kernel sources, function signatures, and more.

Systrack can configure and build kernels for all its supported architectures, and works best at analyzing kernels that it has configured and built by itself.

Installation

Systrack is available on PyPI, it requires Python 3.6+ and is installable through Pip:

pip install systrack        # Base version with no dependencies
pip install systrack[html]  # + HTML output support

Building and installaing from source requires hatch:

hatch build
pip install dist/systrack-XXX.whl       # Base version with no dependencies
pip install dist/systrack-XXX.whl[html] # + HTML output support

Usage

Systrack can mainly be used for two purposes: analyzing or building Linux kernels. For more detailed information, see systrack --help. For information about supported architecture/ABI combinations, see systrack --arch help.

• Building can be done through the --build option. You will need to provide a kernel source directory (--kdir) and an architecture/ABI combination to build for (--arch).

  systrack --build --kdir path/to/linux_git_repo --arch x86-64
  

• Analyzing a kernel image can be done given a vmlinux ELF with symbols, and optionally also a kernel source directory (--kdir). Systrack will extract information about implemented syscalls from the symbol table present in the given vmlinux ELF, and if debugging information is present, it will also extract file and line number information for syscall definitions. Supplying --kdir will help refine and/or correct the location of the definitions, pointing Systrack to the checked-out sources for the right kernel version (the same as the one to analyze).

  Systrack can guess the architecture and ABI to analyze, but if the given kernel was built for support for multiple ABIs, the right one can be selected through --arch.

  systrack path/to/vmlinux
  systrack --format json path/to/vmlinux
  systrack --kdir path/to/linux_git_repo path/to/vmlinux
  systrack --kdir path/to/linux_git_repo --arch x86-64-ia32 path/to/vmlinux
  

Runtime dependencies

• Required: readelf (from GNU binutils) is used to parse and extract ELF metadata such as symbols and sections. This is currently the only compulsory dependency for Systrack to work.
• Optional: addr2line (from GNU binutils) is used to extract location information from DWARF debug info (if available). Without this program, Systrack will not output any information about syscall definition locations.
• Optional: if available, the rg (ripgrep) command is used for much faster recursive grepping of syscall definition locations within kernel sources when needed. Otherwise, slower pure-Python code is used.
• Optional: the jinja2 Python package, which can be either installed separately or automatically (pip install systrack[html]) is used to output interactive HTML pages with a sortable table, links and more. This is the richest output format (selectable with --format html).
• Optional: a working compiler toolchain and kernel build dependencies are obviously needed if you want Systrack to build kernels from source.

Limitations

• Supported kernel images: Systrack works with regular uncompressed vmlinux ELF images and needs ELF symbols. Compressed and stripped kernel images are not supported. Tools such as vmlinux-to-elf can be used to uncompress and unstrip kernel images, after which Systrack will be able to analyze them.
• Old kernel versions: Systrack was mainly designed for and tested on modern kernels (>= v4.0) and has not been tested on older kernels. It should still somewhat work on older kernels, but without the same level of guarantee on the correctness of the output. Support for old kernels may come gradually in the future.
• Relocatable kernel support: Systrack does not currently parse and apply ELF relocations. This means that Systrack does not support kernels using relocation entries for the syscall table. On some architectures (notably MIPS) if the kernel is relocatable the syscall table is relocated at startup and does not contain valid virtual addresses: Systrack will currently fail to analyze such kernels.

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Copyright © 2023-2024 Marco Bonelli. Licensed under the GNU General Public License v3.0.