Libc Component Not Logging

Alexander Boettcher alexander.boettcher at
Sat Aug 8 12:03:08 CEST 2020


On 07.08.20 23:03, Daly, Connor G. wrote:
> Genode beginner here. Been working with the platform for a few weeks trying to port a standard Linux application I wrote to Genode. My program uses sockets, both for sending and receiving, and judging from the code in tcp_terminal, the only way to do sockets is with libc rather than native Genode. I've been trying to implement the first few phases of my program in Genode, but when I run them, no log messages seem to appear and I can't really tell if my program is doing anything. When I remove the libc relevant pieces of code and run my program through a base/Component, everything logs just fine. I created a small test program to find my mistake, so this piece of code does not log anything to qemu with a Linux target platform:

I tried you test program and getting:

[init] child "widget"
[init]   RAM quota:  776K
[init]   cap quota:  16
[init]   ELF binary: widget
[init]   priority:   0
[init -> widget] upgrading quota donation for PD session (0 bytes, 4 caps)
[init] child "widget" requests resources: ram_quota=0, cap_quota=4

The resource request stalls your application until the request gets fulfilled. Since you have a static scenario configured, there is nobody looking at such requests and nobody will respond/upgrade the resource request of your component. Since your scenario is static anyway, you will just have to increase the assigned cap quota of your component, e.g.

-                <default caps="50"/>
+                <default caps="55"/>
                 <start name="widget">

or just a bit more, e.g. 100.

Now I tried to re-run your test, and get:

[init] child "widget"
[init]   RAM quota:  776K
[init]   cap quota:  21
[init]   ELF binary: widget
[init]   priority:   0
affinity 1x1 0x0 1x0 diag=0, label="init -> widget", ram_quota=31996, cap_quota=5
[init] child "widget" requests resources: ram_quota=266240

Again, a resource request, but this time your configured memory is not sufficient. So, I increased it a bit:

                 <default caps="55"/>
                 <start name="widget">
-                                <resource name="RAM" quantum="1M"/>
+                                <resource name="RAM" quantum="1300K"/>

and now I get your "Hello world":

genode build completed
using 'core-linux' as 'core'
using '' as ''
spawn ./core
Genode 20.05-159-g2b601c847f <local changes>
17592186044415 MiB RAM and 8997 caps assigned to init
[init] parent provides
[init]   service "LOG"
[init]   service "PD"
[init]   service "CPU"
[init]   service "ROM"
[init]   service "IO_MEM"
[init]   service "IO_PORT"
[init]   service "RAM"
[init] child "widget"
[init]   RAM quota:  1052K
[init]   cap quota:  21
[init]   ELF binary: widget
[init]   priority:   0
[init -> widget] Hello world
Run script execution successful.

Just some further notes:

If you just porting a normal libc/posix application, without any interactions with Genode services codewise, you can just start with your normal main() entry, e.g.


Additionally, your libc program needs some stdio/stderr/socket etc. configuration, look into the or example, eg. the <vfs> and <libc> xml nodes are crucial, not optional ;-). Since you are doing network, you may also look into repos/libports/run/ as inspiration.

Hope it helps,


Alexander Boettcher
Genode Labs -

Genode Labs GmbH - Amtsgericht Dresden - HRB 28424 - Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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