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

[Richard W. <ri...@no...>]

Am 03.06.2014 03:29, schrieb Nalli, Sanketh:
> I mean, there is only ONE thread in UML that intercepts
> The system calls and services them.
> Can we have more such threads in the kernel ?

UML has no SMP support.

Thanks,
//richard

> -----Original Message-----
> From: Nalli, Sanketh 
> Sent: Monday, June 02, 2014 6:29 PM
> To: use...@li...; 'Richard Weinberger'
> Cc: Volos, Haris
> Subject: RE: [uml-user] invalid /proc/PID/exe in UML processes
> 
> 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
>