Virapix is an application that attaches to other processes using ptrace to monitor and control them. It launches a window manager and attaches to application processes as they are launched. Virapix inserts syscalls like mmap and setpgid into the application's address space and modifies arguments to check for writes and log thread creation events. It signals applications and terminates them before joining with their control threads and the window manager's control thread before shutting down.

1. virapix
App
Virapix Main
Start Virapix
Ctrl Thread
Attach to ptrace
Start Ctrl Thread
Make App Grp Leader
Launch Wnd Mgr
(WM)
Detach App From Parent
Attach To App
Fork State
Stop State
Discard
Signal
Syscall State
Record Mapped
Mem Addr
Modify ArgsCheck For Write
Resume Syscall
Exec State
Clone State
Log Thread
Creation
Def State
Continue
Configure ptrace
options
Signal App
Terminate
App
mmap() args
Insert mmap() in
App Addr Space
SIGSTOP (SYS_mmap)
to App
Wake Parent
Ctrl Thread
setpgid() argsInsert setpgid() in
App Addr Space
mmap() argsInsert mmap() in
App Addr Space
Wait Till Child Proc
Leads New Grp
Wait For App Events
Join With Apps Ctrl
Threads
SIGSHUTDOWN
Apps
Join With WM Ctrl
Thread
First App
Child App
signal other than
SIGTRAP
SIGSHUTDOWN
read only syscall
no handler found
syscall enter
syscall exit
handler found
writes to host
system
normal
inserted
fork
setpgid()
mmap()
from ptrace
(attach)
from virapix (SYS_mmap)
unknown source
exit
SIGSTOP
execve
syscall
clone
default
ICtrl::Run()
execve()
ICtrl::Run()
setpgid()
ptrace()
fork()
Visual Paradigm for UML Community Edition [not for commercial use]