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Denis 'GNUtoo' Carikli, 04/27/2022 02:10 AM


Applications that can be used to do some testing on the device

Projects and/or hardware that can be used to do functional testing


Lava can be used to do functional tests on real hardware. It can be easily installed on PureOS, an FSDG compliant GNU/Linux distribution.


Labgrid has features similar to Lava but it is probably easier to learn because it's probably way easier to get started with it.


The OsmoGSMTester project is able to be interfaced with the Android RIL through ofono and can emulate a GSM network with the help of a compatible GSM base station or SDR.

This presentation from 2019 has many insights on what kind of issue we might expect in interfacing it with smartphones.


The Simtrace 2 project can be used, along with SIM card readers to programmatically feed a SIM card to a smartphone. This can be used to run test on real networks.

Replicant supported devices and testing


  • Antenna connector for the modem
  • The ability to control the device buttons in order to be able to programmatically power on and off the device, and trigger boots into the bootloader and recovery
  • Optionally a way to connect to the serial port, programmatically

Galaxy SII (GT-I9100)

  • The Galaxy SII (GT-I9100) has:
Holding the smartphone in place:
  • The smartphone could either be screwed on a metallic surface or an external case could be screwed on a metallic surface enabling the smartphone not to move.
SIM cards:
  • Simtrace and Simtrace 2 both lacks screw holes so a way must be found to make sure that it doesn't move as it uses flex cables to interface with the SIM socket of the smartphone. That may be fixed in a subsequent hardware revision.

Serial port and USB:



Antenna connector and GSM tower or SDR:
The Galaxy SII (GT-I9100) has two antenna connectors:
  • One internal connector, TODO: find the connector type
  • One external connector, TODO: Find the connector type

Example setup

See also the links inside the Serial_port article for more background on how to get serial port access on devices like the Galaxy SIII (GT-I9300) or the Galaxy SII (GT-I9100).

test infrastructure example (

See for the source of the file.

Using a device without a battery.

  • The Galaxy SIII 4G (GT-I9305) could probably work at lower voltages like 3.3V through the battery connector, but it would require testing it. In that case it might also be a good idea to test it in all configurations (all hardware features being used, cpuburn etc).
  • The 4 pin 'FPC' style battery connector available from amazon, marketed as being for the 'S4 value edition i9515' ( is capable of contacting the Galaxy SIII (GT-I9300)'s battery.


Device Modem antenna connector Compatible software Comments
Motorolla C155 MS-147 * OsmocomBB
* Old Nuttx revisions
Could be used as reference phone as it's probably already supported by the Osmocom testing infrastructure
Galaxy SII (GT-I9100) MS-162 * Replicant 4.0, 4.2, 6.0
* Upstream Linux (partial)
Galaxy Nexus (GT-I9250) ? * Replicant 4.0, 4.2, 6.0 We can get some GSM traces in wireshark with xgoldmon
Galaxy SIII (GT-I9300) ? * Replicant 4.0, 4.2, 6.0
* Upstream Linux (partial)

USB modems

When trying to enable protocol tracing in modems we can connect the device modem (somewhat directly) to a laptop

  • Do we have samsung-ipc on top of the virtual UARTs?
  • The cbd daemon mentioned in the blog post about booting the Galaxy S7 modem doesn't list UART as main link though.
  • Adding the modem USB id when in debug mode (1519:0020) in a search engine shows various usb keys
  • Do phones like the Galaxy SII have smasung-ipc on top of the USB link or UART links when in debug mode?

Pure software setup

lightweight test infrastructure for libsamsung-ipc

It might be possible to have a pure software test infrastructure with libsamsung-ipc.

It could be done more or less like that:

test script <-> ipc-modem or other programs <-> libsamsung-ipc <-> Linux kernel <-> VHCI <-> software sending USB packets

We have several choices for the Linux kernel:

Kernels Comments
User mode Linux (ARCH=um) + Very lightweight, runs completely in userspace
+ Very simple setup. Probably works on armv7 too without dedicated hardware like Intel vt-x
Requires patches for USB / VHCI
- Require dedicated RAM
Linux + libvirt + kvm - Require some virtualization setup that requires dedicated RAM
+ Probably works unpatched
And there is already some projects emulating usb devices:
Project Description comments
gnuk USB token software can build for gnulinux
choptix Library used by gnuk More simple examples
osmo-ccid-firmware1[2][3] CCID emulation Probably uses vusb for testing too




So it might be possible to modify them to send some simple USB packets captured with wireshark / tshark / tcpdump.

user mode Linux

I've already managed to find a configuration that works in an FSDG compliant way:
Settings Status
kernel: kernel_replicant_linux
commit: 843565d21f78 [WIP] ARM: dts: exynos: Add reboot modes to midas
compilation settings: ARCH=um
Host architecture: x86_64
kernel defconfig: x86_64_defconfig
Target Distribution: Parabola x86_64
commandline arguments: ./linux mem=2047M ubd0=parabola.img root=/dev/ubda1
Boots fine
kernel: kernel_replicant_linux
commit: 063228e445e2 net: sipc: core: fix code style
compilation settings: ARCH=um
Host architecture: i686
kernel defconfig: i386_defconfig
Fails to compile1
kernel: linux
commit: f1baf68e1383 Merge tag 'net-5.17-rc4' of [...]kernel/git/netdev/net
compilation settings: ARCH=um
Host architecture: x86_64
kernel defconfig: i386_defconfig
Boots fine
Target Distribution: Replicant 11
Build command: source build/ && lunch uml-userdebug && make dist
kernel: ?
kernel defconfig: ?
Fails to compile2


  CC      arch/x86/um/user-offsets.s
cc1: error: code model ‘large’ not supported in the 32 bit mode
cc1: sorry, unimplemented: 64-bit mode not compiled in
make[1]: *** [scripts/ arch/x86/um/user-offsets.s] Error 1
make: *** [arch/um/Makefile:118: archprepare] Error 2


[ 52% 179/339] including external/mesa3d/ ...
In file included from build/make/core/
In file included from external/mesa3d/
In file included from external/mesa3d/src/mesa/
external/mesa3d/src/mesa/ error: BUILD_HOST_STATIC_LIBRARY is obsolete. Please convert to Soong.
12:25:14 ckati failed with: exit status 1

#### failed to build some targets (02:04 (mm:ss)) ####

Booting Parabola

To run Parabola first you need to create an image.
Then you need to chroot (with arch-chroot) insde the image and change the password.
Once you exited the chroot and unmounted the image and removed the loop mapping, you can boot it.

During boot you'll see a message like that at the end:

Virtual console 1 assigned device '/dev/pts/4'

You can then login in this way:

$ sudo picocom /dev/pts/4 
picocom v3.1

port is        : /dev/pts/4
flowcontrol    : none
baudrate is    : 9600
parity is      : none
databits are   : 8
stopbits are   : 1
escape is      : C-a
local echo is  : no
noinit is      : no
noreset is     : no
hangup is      : no
nolock is      : no
send_cmd is    : sz -vv
receive_cmd is : rz -vv -E
imap is        : 
omap is        : 
emap is        : crcrlf,delbs,
logfile is     : none
initstring     : none
exit_after is  : not set
exit is        : no

Type [C-a] [C-h] to see available commands
Terminal ready

parabola login: root
[root@parabola ~]# cat /etc/os-release 
PRETTY_NAME="Parabola GNU/Linux-libre" 
[root@parabola ~]# 

network support

With vec0:transport=raw,ifname=p-veth0,depth=128,gro=1 in Linux command line, we can have a regular Ethernet interface that can be configured as usual, bridges also work.

See the kernel documentation (user_mode_linux_howto_v2.rst) for more details on how to setup UML networking.

USB support

With Linux 5.17-rc3 it's possible to have USB in user-mode-linux and I validated it by exporting an rtl_sdr with usbip and testing the receiving of FM with rtl_fm -f 88M | hexdump -C.

It seems to be there since Linux 5.14 since this commit:
68f5d3f3b654 um: add PCI over virtio emulation driver

Unfortunately we use Linux 5.10.70 in replicant 11 right now.

User Mode Linux TODO
  • We probably need to make i686 and armv7 to work too.
  • We also need to setup USB somehow with vhci_hcd and so on
  • We need to make USB work with Replicant 11 kernel or upgrade the Replicant 11 kernel.
  • We still need to find a very simple stack to send URBs.
  • We then need to test it for real, see if we can collect kernel crashes in this way and so on.

Updated by Denis 'GNUtoo' Carikli 28 days ago · 54 revisions

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