{{ 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-firmware[1][2][3] | CCID emulation | Probably uses vusb for testing too | fn1. https://git.osmocom.org/osmo-ccid-firmware/tree/ccid_host fn2. https://git.osmocom.org/osmo-ccid-firmware/tree/ccid_host/README.linux-dummy_hcd-ffs fn3. https://media.ccc.de/v/osmodevcon2019-128-osmo-ccid-firmware-libosmocore-talloc-on-uc-usb-testing-from-ttcn-3 So it might be possible to modify them to send some simple USB packets captured with wireshark / tshark / tcpdump. h4. 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 compile[1] | | *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/envsetup.sh && lunch uml-userdebug && make dist *kernel*: ? *kernel defconfig*: ? | Fails to compile[2] | fn1. 
  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/Makefile.build:117: arch/x86/um/user-offsets.s] Error 1
make: *** [arch/um/Makefile:118: archprepare] Error 2
fn2. 
[ 52% 179/339] including external/mesa3d/Android.mk ...
FAILED: 
In file included from build/make/core/prebuilt.mk:53:
In file included from external/mesa3d/Android.mk:124:
In file included from external/mesa3d/src/mesa/Android.mk:23:
external/mesa3d/src/mesa/Android.libmesa_glsl_utils.mk:74: 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)) ####
h5. 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
Password: 
[root@parabola ~]# cat /etc/os-release 
NAME="Parabola"
PRETTY_NAME="Parabola GNU/Linux-libre"
ID=parabola
ID_LIKE=arch
BUILD_ID=rolling
ANSI_COLOR="1;35"
HOME_URL="https://www.parabola.nu/"
DOCUMENTATION_URL="https://wiki.parabola.nu/"
SUPPORT_URL="irc://chat.freenode.net#parabola"
BUG_REPORT_URL="https://labs.parabola.nu/"
LOGO=parabola
[root@parabola ~]#
h5. 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. h5. 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. h5. 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. * We also need to package user-mode-linux in Parabola or other FSDG distributions to make testing easier.