Re: [uml-user] invalid /proc/PID/exe in UML processes

[Nalli, S. <san...@hp...>]

Okay, so I've found a way around the invalid exe symlink.
I don't need that anymore.
The next challenge is concurrency in UML.

I wrote a simple program that launches 10 pthreads,
Each of which makes some system calls in an infinite loop.

I notice that even though there are 10 threads in my dummy program,
There is only ONE UML kernel thread. Is this correct ?
If so, does this mean that UML kernel is serializing the execution ?
Is there some way of making UML kernel multi-threaded ?

-----Original Message-----
From: Richard Weinberger [mailto:ri...@no...] 
Sent: Monday, June 02, 2014 1:46 PM
To: Nalli, Sanketh
Cc: use...@li...
Subject: Re: [uml-user] invalid /proc/PID/exe in UML processes

Am 02.06.2014 22:42, schrieb Nalli, Sanketh:
> Nope, but here is some bootlog

Hmm, I have no idea so far.

Applications running under valgrind or other debuggers suffered from the issue that /proc/pid/exe is empty.

> The host does not have skas3 patch
> Do you think that is the problem ?

Nope. SKAS0 works fine.

> Which host shd I use that already has this patch (I mean I cud patch 
> the host myself but if there is one Already present, that is good !)
> 
> Core dump limits :
>         soft - 0
>         hard - NONE
> Checking that ptrace can change system call numbers...OK Checking 
> syscall emulation patch for ptrace...OK Checking advanced syscall 
> emulation patch for ptrace...OK Checking for tmpfs mount on 
> /dev/shm...nothing mounted on /dev/shm Checking PROT_EXEC mmap in 
> /tmp/...OK Checking for new_mm and switch_mm support in the host:
>         /proc/self/mm ... Failed -
> No such file or directory
> Checking for the skas3 patch in the host:
>   - /proc/mm...not found: No such file or directory
>   - PTRACE_FAULTINFO...not found
>   - PTRACE_LDT...not found
> UML running in SKAS0 mode
> Adding 20606976 bytes to physical memory to account for exec-shield 
> gap Linux version 2.6.24-g91525300-dirty 
> (jd...@am...) (gcc version 4.1.1 20070105 (Red Hat 
> 4.1.1-51)) #1 Mon Jan 28 12:03:41 EST 2008

Wow. This UML is horrible old.

Thanks,
//richard