Linux /Proc File System for Embedded Systems

원문: http://www.opentech.at/papers/embedded_proc/embedded_proc.html

The Linux Proc File System for Embedded Systems
Concepts and Programing

Nicholas Mc Guire
Opentech.at
Hollabrunn, Austria
der.herr@hofr.at, http://www.opentech.at

Abstract:

Since the late 0.99.X releases of the Linux kernel the proc file system is included in many GNU/Linux systems. This virtual file system interface allows both the inspection of kernel internal data structures and the manipulation of these data structures without the need of additional non-volatile memory. In embedded systems with tight resource constraints, the file system footprint is a key issue, in addition to the requirement for run-time optimisation. For such systems, utilising the capabilities of the proc file system and the related sysctl functions in order to provide kernel related administrative information via proc, as well as resource-optimised control interfaces, can substantially ameliorate embedded systems performance. A further, often ignored aspect, is that the proc and sysctl interface allow very precise tuning of access permissions, both increasing the security of the embedded system's administrative interfaces and improving diagnostic precision, which is essential for efficient error detection and analysis.

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• Introduction
• Proc Basics
  • Performance
    • System calls
    • Optimised file operations possible
    • File system overhead
    • Module size vs. User-space App
  • Portability
    • proc functions
    • Bound to kernel release
  • Security
    • Modifying kernel code
    • Utilisation of kernel capabilities on a file scope
• Proc API vor Kernel 2.4.X
  • Proc core structures
    • proc_dir_entry
    • proc file operation
  • General proc functions
    • create_proc_entry
    • create_proc_read_entry
    • create_proc_info_entry
    • proc_mkdir
    • proc_symlink
    • proc_mknod
    • remove_proc_entry
  • Subsystem specific wrapper functions
    • proc_net_create
    • proc_net_remove
  • /proc/sys Sysctl functions list
    • register_sysctl_table
    • unregister_sysctl_table
    • ctl_table
    • ctl_table hirarchy
  • basic proc_handlers
  • Predefined proc callbacks
    • proc_dostring
    • proc_dointvec
    • proc_dointvec_bset
    • proc_dointvec_minmax
    • proc_dointvec_jiffies
    • proc_doulongvec_minmax
    • proc_doulongvec_ms_jiffies_minmax
  • Using regular Library Functions
  • Kernel `libc` Functions
    • memory functions
    • string functions
    • type-conversion functions
  • Related Kernel functions
    • copy_from_user
    • MKDEV
    • SET_MODULE_OWNER
• Managment Interfaces via proc
  • Available tools
  • /proc/top a comparison
    • Comparing resources
    • proc_top.c
    • proc_ifconfig.c
• RT-Interfaces via proc
  • Task control via /proc
  • Exporting RTLinux-internals via /proc
  • Security Issues
• Conclusion
• Acknowledgement
• Bibliography
• About this document ...