Re: Regarding getrandom syscall

[Manuel Pégourié-Gonnard]

Hi,

Maybe your unistd.h comes from an older kernel? That would explain why
it doesn't define that symbol.

Here [1] is some code using that syscall successfully, you can see it
looks a lot like Sayutin's code, except it does a few more compile-time
and runtime checks to fallback on using /dev/urandom if necessary.

[1]:
https://github.com/ARMmbed/mbedtls/blob/dd9895d8101f17ce804830472cbb140eba1c46a0/library/entropy_poll.c#L85

Manuel.


On 21/06/2016 15:41, Avantika Rawat wrote:
> Hi,
> 
> Thanks for the suggestion but i am getting following error
> 
>  error: 'SYS_getrandom' undeclared (first use in this function)
> 
> then i have replaced the SYS_getrandom by 275 in syscall(275, -- args--);
> as 275 is the  __NR_getrandom defines in unistd.h file,  but it is
> returning -1.
> Can somebody tell me what i am missing here??
> 
>  . Also in /proc/kallsyms it is showing two syscalls added for getrandom
> 
> 80417a38 T SyS_getrandom
> 80417a38 T sys_getrandom
> 
> On Sat, Jun 18, 2016 at 7:12 PM, Sayutin Dmitry  wrote:
>> Well, in fact it is not hard.
>>
>> Just use syscall(2) provided by libc.
>>
>> You need to provide to this function syscall id and syscall args.
>> Syscall id can be retrieved from macro constant
>> Should look something like:
>>
>> #define _GNU_SOURCE
>> #include 
>> #include 
>>
>> syscall(SYS_getrandom, -- your - args - here --);
>>
>> It returns long value - the result of syscall.
>> If it is between [-4095; -1] then it is negated errno, otherways it is 
>> return value.
>>
>>
>> 18.06.2016, 16:32, "Anoop" :
>>> Hi Avantika,
>>>
>>> On Sat, Jun 18, 2016 at 5:32 PM, Avantika Rawat  
>>> wrote:
  Hi ALL,

  I am trying to use getrandom syscall in kernel 3.10.20 by following this
  link

  
 https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c6e9d6f38894798696f23c8084ca7edbf16ee895

  i have compiled the kernel and now want to call the getrandom syscall from
  userspace to generate random numbers. But i am getting following error 
 while
  calling the getrandom () from userspace.

  (.text.startup+0x18): undefined reference to `getrandom'
  (.text.startup+0x1c): undefined reference to `getrandom'
>>>
>>> Your user space program will not know where 'getrandom' is defined
>>> unless it's in the C library. You need to research more on how to call
>>> custom system calls.
>>>
>>> -Anoop
>>>
  --
  Regards,
  Avantika Rawat

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>>
>> -
>> Sayutin Dmitry 
> 
> 
> 

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Re: oh yeah

[Anuz Pratap Singh Tomar]

On Tue, Jun 21, 2016 at 3:05 PM, ty armour  wrote:

> if you all want to you can build computers microchip by microchip, just
> post tutorials on it if you do!
>
> these are fun things to think about. IM like a few years out but im sure
> ill get it done
>
> I would recommend this
http://kernelnewbies.org/mailinglistguidelines



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-- 
Thank you
Warm Regards
Anuz
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oh yeah

[ty armour]

if you all want to you can build computers microchip by microchip, just
post tutorials on it if you do!

these are fun things to think about. IM like a few years out but im sure
ill get it done
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cool

[ty armour]

yeah ill take a read through them.

I am working on building my own computers and cnc machines either analog or
microchip by microchip and im sure these will help me.

ill figure it out

but yeah also look for analog computers in a few years.

thanks
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Re: Regarding getrandom syscall

[Avantika Rawat]

Hi,

Thanks for the suggestion but i am getting following error

 error: 'SYS_getrandom' undeclared (first use in this function)

then i have replaced the SYS_getrandom by 275 in syscall(275, -- args--);
as 275 is the  __NR_getrandom defines in unistd.h file,  but it is
returning -1.
Can somebody tell me what i am missing here??

 . Also in /proc/kallsyms it is showing two syscalls added for getrandom

80417a38 T SyS_getrandom
80417a38 T sys_getrandom

On Sat, Jun 18, 2016 at 7:12 PM, Sayutin Dmitry  wrote:
> Well, in fact it is not hard.
>
> Just use syscall(2) provided by libc.
>
> You need to provide to this function syscall id and syscall args.
> Syscall id can be retrieved from macro constant
> Should look something like:
>
> #define _GNU_SOURCE
> #include 
> #include 
>
> syscall(SYS_getrandom, -- your - args - here --);
>
> It returns long value - the result of syscall.
> If it is between [-4095; -1] then it is negated errno, otherways it is return 
> value.
>
>
> 18.06.2016, 16:32, "Anoop" :
>> Hi Avantika,
>>
>> On Sat, Jun 18, 2016 at 5:32 PM, Avantika Rawat  
>> wrote:
>>>  Hi ALL,
>>>
>>>  I am trying to use getrandom syscall in kernel 3.10.20 by following this
>>>  link
>>>
>>>  
>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=c6e9d6f38894798696f23c8084ca7edbf16ee895
>>>
>>>  i have compiled the kernel and now want to call the getrandom syscall from
>>>  userspace to generate random numbers. But i am getting following error 
>>> while
>>>  calling the getrandom () from userspace.
>>>
>>>  (.text.startup+0x18): undefined reference to `getrandom'
>>>  (.text.startup+0x1c): undefined reference to `getrandom'
>>
>> Your user space program will not know where 'getrandom' is defined
>> unless it's in the C library. You need to research more on how to call
>> custom system calls.
>>
>> -Anoop
>>
>>>  --
>>>  Regards,
>>>  Avantika Rawat
>>>
>>>  ___
>>>  Kernelnewbies mailing list
>>>  Kernelnewbies@kernelnewbies.org
>>>  http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>>
>> ___
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>> Kernelnewbies@kernelnewbies.org
>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
> -
> Sayutin Dmitry 



-- 
Regards,
Avantika Rawat

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Re: boot param to change tick

[Rami Rosen]

Hi,
>You have to rebuild the kernel to change the HZ value.
+1

Rami Rosen

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Re: What is the point of this function?

[Andrea Benelli]

So, it's just an override?
Why return true and not false?
Il 21 giu 2016 4:32 AM, "Nathan Williams"  ha scritto:

> On Tue, 2016-06-21 at 00:48 +0200, Andrea Benelli wrote:
> > Hello, i was looking at the linux/sched.h (kernel version 4.6.2)
> > source code and i found this function at line 1174:
> >
> > static inline bool cpus_share_cache(int this_cpu, int that_cpu)
> > {
> > return true;
> > }
> >
> > I'm not able to understand the utility of a function that just return
> > a true value.
> > i've noticed that there are a lot of functions like this (function
> > that just return a constant).
>
> Hi Andrea,
>
> That's the case for when CONFIG_SMP isn't defined. What happens when
> CONFIG_SMP is defined?
>
> I suggest having a look through the code with a Linux cross reference:
>
> http://lxr.free-electrons.com/ident?v=4.6;i=cpus_share_cache
>
> Regards,
> Nathan
>
>
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Re: looking for tutorials

[Daniel Baluta]

On Mon, Jun 13, 2016 at 5:43 PM, ty armour  wrote:
> I need tutorials on kernel development. And on complete operating system
> development. I would prefer them to be in assembly because it is faster, but
> it seriously needs to get done.
>
> If you are interested, simply post all of the tutorials and other relevant
> information to coding kernels that you can
>
> and show the references, like actually say okay so in order to do this we
> need to look for this in the assembler manual.
>
> Thanks and have fun

You can start by reading the code for lguest:

http://lxr.free-electrons.com/source/drivers/lguest

It has very good documentation and it covers a lot of
OS fundamental blocks.

Daniel.

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Re: looking for tutorials

[Anuz Pratap Singh Tomar]

On Mon, Jun 13, 2016 at 3:43 PM, ty armour  wrote:

> I need tutorials on kernel development. And on complete operating system
> development. I would prefer them to be in assembly because it is faster,
> but it seriously needs to get done.
>
> If you are interested, simply post all of the tutorials and other relevant
> information to coding kernels that you can
>
> and show the references, like actually say okay so in order to do this we
> need to look for this in the assembler manual.
>
> Thanks and have fun
>
>
If you look at the Archives I posted a lot of links in a mail few weeks
ago.

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-- 
Thank you
Warm Regards
Anuz
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Re: looking for tutorials

[Robert P. J. Day]

On Mon, 13 Jun 2016, ty armour wrote:

> I need tutorials on kernel development. And on complete operating
> system development. I would prefer them to be in assembly because it
> is faster, but it seriously needs to get done.
>
> If you are interested, simply post all of the tutorials and other
> relevant information to coding kernels that you can
>
> and show the references, like actually say okay so in order to do
> this we need to look for this in the assembler manual.

  perhaps you'd like a hot oil massage and a nice chablis while you
wait.

rday

-- 


Robert P. J. Day Ottawa, Ontario, CANADA
http://crashcourse.ca

Twitter:   http://twitter.com/rpjday
LinkedIn:   http://ca.linkedin.com/in/rpjday



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Re: IPV6 Multipath support

[Narasimha M]

Hi,

Could some one please update as this is very urgent for me. I am not
able to proceed further.

Thanks

On Mon, Jun 20, 2016 at 5:33 PM, Narasimha M  wrote:
> Hi All,
>
> I am using linux kernel 3.10.20, and tried to add multipath routes
> using the below commands.
>
> ip -6 route add default nexthop via ::1 dev eth1 weight 1 nexthop
> via ::2 dev eth0 weight 1.
>
> But when i run the traffic to the host reachable to both the
> interfaces, traffic is always going through eth1, which means the
> multipath routing is not working.
>
> Could you please let us know that do we have multipath support for
> ipv6 in linux3.10.20 kernel ?
>
> Thanks in advance.



-- 
Narasimha

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