LiteBSD for MIPS-based systems with some of my fixes
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README.md

LiteBSD

This is my private copy of LiteBSD with some fixes for problems I encountered. So far, everything is tested on qemu-system-mipsel and the WIFIRE PIC32MZ board.

As of now, the bugfixes are:

  1. support for KTRACE

    • when enabling KTRACE in the kernel config, trying to trace a process results in a kernel panic due to trying to release a lock in sys/kern_lock.c (l. 352). The current lock holder is set to LK_KERNPROC (pid -2), which - according to sys/lock.h - indicates that no process holds an exclusive lock.
  2. fix the execution of #! executables

    • The code implementing the execve system call is different to either the 4.3 or 4.4BSD implementations (sys/kern_exec.c) I could find online. The existence of the "shebang" (#!) magic is tested in the getheader function. When getheader detects this, it tries to set the real executable to the one given after #!; however, this is not returned to execve from getheader (other BSD implementations implement the getheader functionality inside the execve function).

      This is important since, if #! was detected, execve jumps (yep, goto...) to its own start and re-executes with the new executable name (to be exact, a new struct nameidata) - which was, hoever, never set. I changed getheader to return a pointer to the new nameidata for the real executable and moved the again label one line down to avoid re-initializing the nameidata from scratch.

      When doing this, the kernel crashed due to a double free, probably due to the call to "FREE(ndp->ni_cnd.cn_pnbuf, M_NAMEI);" in step 2 in execve. This is currently commented out.

      TODO: I will have to investigate if this is the real fix for the double free problem or if this causes a memory leak...

Enjoy, Michael Engel (engel@multicores.org)


Here's the original README:

LiteBSD is a variant of 4.4BSD operating system adapted for microcontrollers. Currently, only the Microchip PIC32MZ family is supported as a target. It is equipped with MMU with paging support, and 512kbytes of on-chip RAM. These resources are enough to build a compact networked embedded system.

For more information, see LiteBSD Wiki pages.

Precompiled binaries for several PIC32MZ boards are available from Autobuild Download page.

If you are looking for the LiteBSD ports tree please see this repository.