L4Linux - FAQ!

Can I build in a separate directory than the source directory?
Yes, this is possible with Linux 2.6. Use O=../your/obj/dir for every make call.

The colors under DOpE or con look strange.
Most probably you have configured L⁴Linux with the VGA driver. Disable it (Device Driver -> Graphics Support -> Console display driver support -> VGA text console). While you are at it, also disable the mouse and keyboard drivers if you haven't done so already.

The mouse is trapped inside the DOpE window!
Press the 'Break' key to release it.

Under Fiasco-UX, I'm getting an error like this while starting L⁴Linux:

KERNEL: 11.3 (tcb=20441800) killed:
Unhandled trap
EAX 005feb30 EBX 000003c0 ECX 00000000 EDX 000003da
ESI 000003da EDI 000003c0 EBP 00635f30 ESP 00635f20
EIP 0064e3da EFLAGS 00210046
CS 0002 SS 002b DS 002b ES 002b FS 0000 GS 0007
trapno 13, error 00000000, from user mode
(internal event regarding GDT entry no. 0x00)

Your image probably still contains a driver or similar which tries to access the hardware. Under Fiasco-UX this will result in an exception. To find out which feature to disable in the Linux configuration, enter the kernel debugger with Ctrl-C, and enter ut11 64e3da[ENTER] to show a disassembly of task 11 at address 0x64e3da. Scroll a bit up to see the C file of the code. Now that you know the C file you can disable the appropriate option in the kernel configuration.

I want to run a Linux application which also uses L4 services (so called hybrid programs).
This is generally possible but needs careful programming as those programs are in both worlds (Linux and L4). Nevertheless those programs are Linux programs, and additionally are using L4 services. Using L4 IPC to other L4 threads is usually no problem, as well as other L4 system calls. But do not modify the address space of your Linux program, by mapping memory into it, creating other threads or similar (except when you exactly know when you can do so).

I want to use a driver that kmalloc's GFP_DMA memory (e.g. SCSI drivers, floppy, SATA disks).
GFP_DMA memory is memory that comes from the first 16MB of the physical memory. It is meant for ISA DMA. To make such memory available to L⁴Linux, dm_phys has to reserve memory in this area with the '--isa' argument (e.g. --isa=0x00800000).
If L⁴Linux was able to request ISA DMA memory from dm_phys it will say so in it's startup messages. If there are no messages indicating success something has got wrong. To debug, start dm_phys with the -v switch to see the memory pool allocations and if a large enough physically continuous chunk of memory in the 7th pool could be allocated. Large enough is something about 2MB, depending on the specific L⁴Linux configuration.

Using the floppy crashes L⁴Linux.
You need to configure ISA DMA memory, see above.

Detecting SATA disks or USB storage crashes L⁴Linux while booting up.
You need to configure ISA DMA memory (yes, really), see above.

noreplacement kernel command line option
Do not use the noreplacement kernel command line option anymore.