On Mon, Jun 2, 2014 at 7:55 PM, Nalli, Sanketh <sanketh.na...@hp.com> wrote: > Thanks a lot. > > Do you know why my /proc is empty in the guest
Did you mount procfs? > And why does the /proc/PID/exe NOT point to anything in > > The host ? (PID is the pid of a dummy program running in UML) Host PID != Guest PID > > > From: enjoy mindful [mailto:enjoymind...@gmail.com] > Sent: Friday, May 30, 2014 12:06 AM > To: Nalli, Sanketh > Cc: user-mode-linux-user@lists.sourceforge.net > Subject: Re: [uml-user] invalid /proc/PID/exe in UML processes > > > > let me answer your second question. > > I did this analysis with kernel linux-3.12.6: > > 1) make ARCH=um cscope > 2) search functions which called 'clone' > File Function Line > 0 ubd_user.c start_io_thread 43 pid = clone(io_thread, (void *) sp, > CLONE_FILES | > CLONE_VM, NULL); > 1 helper.c start_io_thread 74 pid = clone(helper_child, (void *) sp, > CLONE_VM, &data); > 2 helper.c start_io_thread 124 pid = clone(proc, (void *) sp, flags, > arg); > 3 process.c start_userspace 300 pid = clone(userspace_tramp, (void *) sp, > flags, (void *) > stub_stack); > 4 lguest.c create_thread 1048 vq->thread = clone(do_thread, stack + > 32768, CLONE_VM | > SIGCHLD, vq); > > 3) insert some printk statement in those function > 4) build and run, then watch the booting process output > [root@localhost ~]# dmesg | grep 6436 > [ 0.190000] run_helper_thread : clone success, pid = 6436 > [root@localhost ~]# dmesg | grep 6437 > [ 0.190000] start_io_thread - clone success : pid = 6437 > [root@localhost ~]# dmesg | grep 6438 > [ 0.190000] run_helper_thread : clone success, pid = 6438 > > [real@real runuml]$ ps -ef | grep patch > real 6423 1553 6 16:17 pts/0 00:00:02 ./linux_patched > ubda=./Fedora20-x86-root_fs mem=256m > real 6436 6423 0 16:17 pts/0 00:00:00 ./linux_patched > ubda=./Fedora20-x86-root_fs mem=256m > real 6437 6423 0 16:17 pts/0 00:00:00 ./linux_patched > ubda=./Fedora20-x86-root_fs mem=256m > real 6438 6423 0 16:17 pts/0 00:00:00 ./linux_patched > ubda=./Fedora20-x86-root_fs mem=256m > real 6439 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6459 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6479 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6492 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6565 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6567 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6572 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6573 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6576 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6605 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6619 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6621 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6707 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6715 6423 0 16:17 pts/0 00:00:00 [linux_patched] > real 6765 6423 0 16:18 pts/0 00:00:00 [linux_patched] > > [root@localhost ~]# dmesg | grep proc > [ 0.090000] run_helper_thread : clone success, pid = 8387, proc=0806471d > [ 0.100000] run_helper_thread : clone success, pid = 8389, proc=080663a3 > > [real@real linux-3.12.6]$ grep 0806471d System.map > 0806471d t aio_thread > [real@real linux-3.12.6]$ grep 080663a3 System.map > 080663a3 t write_sigio_thread > > so, the four processes are: > 1) uml kernel main thread > 2) aio_thread > 3) io_thread > 4) write_sigio_thread > > > > On Fri, May 30, 2014 at 9:22 AM, Nalli, Sanketh <sanketh.na...@hp.com> > wrote: > > Hi, > > So I start UML with the cmdline > > ./linux rootfstype=hostfs rw mem=1G init=/bin/bash > > > > When the bash shell comes up, I run my prog : ./my_prog > > > > 6173 pts/8 00:00:00 linux > > 6180 pts/8 00:00:00 linux > > 6181 pts/8 00:00:00 linux > > 6182 pts/8 00:00:00 linux > > 6183 pts/8 00:00:00 linux > > 6188 pts/8 00:00:13 linux > > > > > > The last item in the list with PID is 6188 is my program. > > I can tell because my_prog increments a counter in an infinite loop > > And consumes CPU cycles. It shows up on “top” as the dominant process. > > > > My question: > > 1. /proc/6188/exe is invalid. Why ?? > > I mean, it doesn’t point to anything. > > Shouldn’t it point to my_prog or something ? > > > > 2. What do the 4 UML processes 6173, 6180, 6181, 6182 do ? (6183 is > /bin/bash whos “exe” symlink is also doesn’t point to anything !!) > > 3. When a UML process, say my_prog (PID 6188) makes a system call, > where is the system call executed – is it within the addr space of 6173 (the > UML kernel process) or 6188 (my_prog running in UML ??) > > > > -Sanketh > > > > > > > ------------------------------------------------------------------------------ > Time is money. Stop wasting it! 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