An In-Kernel x86 Disassembler For Linux Kernel
Written by Michael Larabel in Linux Kernel on 2 April 2012 at 07:44 AM EDT. 11 Comments
Patches for an x86 disassembler for the Linux kernel have been proposed. An in-kernel disassembler could prove useful for developers in cases of kernel panics and other happenings.

Masami Hiramatsu, the developer behind this x86 disassembler patch-set writes on the mailing list, "Here is a series of patches of the in-kernel x86 disassembler for the latest tip tree. This will show you a pretty disassembled code instead of just a digital code sequence when you gets a kernel panic etc. (I know, we also have script/decodecode for the panic use) This feature is not for users, but mainly for kernel developers who can understand disassembly code of x86 ;)."

This implementation provides a debugfs-based disassembler interface to disassemble a running Linux kernel, panic dumps show disassembly code instead of the instruction byte stream (a more human-friendly report to debug), a disassemble command for the KDB kernel debugger, and a user-land disassembly tool.

Right now though only common x86 instructions are supported but not items like SEE, MMX, and AVX.

Ingo Molnar has already responded with some feedback and ideas, including the idea of now introducing a built-in x86 assembler for the Linux kernel. "Another very interesting usecase would be to invert it and create a simpler parser and an in-kernel *assembler*: a GAS replacement in essence. We could build the kernel using its own assembler. That could also be used for safe sandboxing: the disassembler could be combined with the assembler to ensure that binary code submitted to the kernel is 'safe' to execute - even in kernel-space. A sha1 hash could be used to cache already checked, 'safe' modules of code."

It's now past the Linux 3.4 kernel merge window but this disassembler could be a potential feature for the Linux 3.5 kernel.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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