Pram Fs
Squash Fs

嵌入式 Linux 知识库

From: eLinux.org

Pram Fs Specification

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Contents

Introduction

This page specifies a file system that will enhance security of system data in the presence of kernel bugs or rogue programs.

Rationale

A single bug in the Linux kernel may cause catastrophic damage to a system. If a product holds irreproducible security keys, financial data, or account information, then loss of such data could render the product unusable, or worse. The customer could suffer financial or legal harm (from account theft or identity theft).

It is not possible to guarantee with certainty that there are no bugs in the Linux kernel. However, it is possible to decrease the probability that a bug in the kernel will cause damage to a particular area of memory or storage. This protected area could then be used with greater confidence to hold sensitive user or product data.

Portions of the product memory and storage should be made resistant to kernel bugs. A protected RAM file system would remain consistent if any of the kernel data pointers are corrupted, or if the kernel starts executing unexpectedly in the wrong location.

Specifications

  1. A configuration option for the Linux kernel SHALL be provided which controls whether or not the kernel supports the PRAM file system. This option MUST be called CONFIG_PRAM_FS. 2. A full-featured read/write file system for Linux that is RAM-based.
  2. If the memory is non-volatile, the file system SHALL be persistent.
  3. File I/O in PRAMFS is always direct, synchronous, and never blocks.
  4. PRAMFS should be write-protected.
  5. In case there are systems where the write protection is not possible, this feature can be disabled with the CONFIG_PRAMFS_NOWP configuration option.

Notes (informational and non-normative)

There is only minimal effort required to back-port the 2.4.22 version of the PRAMFS patch set to the CELF source tree.

References

Patches are available for PRAMFS against the kernel.org trees for kernel versions 2.4.22 and 2.6.4 at http://pramfs.sourceforge.net.

Remaining Issues

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