please disable CONFIG_STRICT_DEVMEM (for flashrom)

Topics about the system utilities that are not related to Hard-disk and storage
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Joined: 20 Apr 2016, 20:10

please disable CONFIG_STRICT_DEVMEM (for flashrom)

Postby carangil » 20 Apr 2016, 20:16


Your CD is awesome, and its great that it includes flashrom. However, for some hardware (namely, mine, satasii), I flashrom needs to mmap /dev/mem in a place not normally allowed in order to do some memory mapped io. The requires that PAT is disabled, along with STRICT_DEVMEM disabled. PAT can be disabled by 'nopat' on the kernel command line, and probably shouldn't be disabled by default. This is easy, I can press 'tab' on boot and change the command line. However, CONFIG_STRICT_DEVMEM is a kernel compile-time option. If it is disabled, you can read/drive /dev/mem for all system memory. It is enabled by default on most new kernels, since it is a major security risk. However, on a system recovery CD, you want access to everything.

(Note: some websites mention an kernel command line option strict-devmem=0, this does not appear to work, and is not honored by kernels anymore. Otherwise someone as root can put it in grub.cfg, reboot the machine, and access everything: It can only be disabled in the kernel at compile time.)

I probably have to go about compiling my own kernel now, but maybe fixing this on the next revision will help others.

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