I am using a Lenovo T520 laptop and Genode version 15-11. If I run seoul-fancy.run with the the bzImage-3.1 and tc-browser.gz (downloaded by the script from genode.org), I succeed in booting into an X environment after clicking on the init button when Genode's window manager comes up. Therefore, I know I have compiled the tools and enabled my build environment correctly.

Then I replaced the kernel: bzImage-3.1 and initrd:  tc-browser.gz with a custom-compiled bzImage ( I need to enable an additional kernel feature), and the standard core.gz. I modified the run script so they would download from my web server running on localhost.

I am then  loading the minimal TC extensions (after booting to the shell) to load the X windows environment:

Using the standard cmdline in the seoul-fancy.run script, the network would not start, so I added init=linuxrc to the cmdline, which made the network work. However some values of vga=xxx break the network (no IP address). 

No matter what is the issue with the network, I can find no way to make startx to work, regardless of which values for vga I use from this table ( the standard seoul-fancy.run script used 0x314 = 791 in the table below.

Color     640x480     800x600      1024x768     1280x1024

   256    8 bit     769         771           773          775

 32000   15 bit     784         787           790          793

 65000   16 bit     785         788           791          794

 16.7M   24 bit     786         789           792          795

Does anyone have a working solution?