[User-mode-linux-devel] I added a tour of the source to the web site

[Cedric A. <ad...@in...>]

Jeff Dike writes:
 > It's at http://user-mode-linux.sourceforge.net/tour.php and it contains 
 > write-ups of the system call mechanism and the network driver.
 > 
 > I'd appreciate you looking at it and letting me know what you think
 > about it.
 > 
 > I'd also appreciate any and all contributions to it.  If you're 
 > interested in 
 > grokking a hunk of the code and writing it up, let me know, and 
 > I'll fill you 
 > in on the php and the hacked-up lxr in the background.

  The text is quite helpful. It is exactly what I tried to figure out.
The problem with UML is that the tracing thread is started in a
clone() call, and is difficult to debug: do you have a special gdb
with clone() support ? Or do you simply attach the process later ?

I tried to run the input thread in a clone() [instead of signals()] and to
"mov <signals() info>,%ecx ; mov <new tracing thread stack>,%eax;
mov %eax,%esp ; push %ecx ; call <signals>". But for some reason the
process crashes much _before_ reaching this modification (because argv/argc
become invalid, because of the remaps???)

  What stays also unclear is whether the linux kernel is actually 
run as the "tracing thread", and how memory manipulations are performed,
when a process calls "brk()" for instance. I guess gdb
the tracing thread is necessary for figuring out.

Cheers,
-- Cedric