is memcpy a system call?

is memcpy a system call?

[J.Hwan Kim]

Hi, everyone

Is memcpy a system call?

Thanks in advnace,

Best Regards,
J.Hwna Kim

is memcpy a system call?

[rahul dev]

> Is memcpy a system call?
> 
> Thanks in advnace,
> 

memcpy is *not* a system call. It is a standard C library function.
System calls are those where you enter the kernel mode and ask your OS to do something for you (like read/write from disk).

For memory copy you don't need to take the service of OS. 

is memcpy a system call?

[siddharth saxena]

Hi

Memcpy is both- a system call as well as a user library function.
Implementation differs

Regards
Siddharth
On Jun 8, 2012 8:42 PM, "J.Hwan Kim" <frog1120@gmail.com> wrote:

> Hi, everyone
>
> Is memcpy a system call?
>
> Thanks in advnace,
>
> Best Regards,
> J.Hwna Kim
>
>
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
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is memcpy a system call?

[Jonathan Neuschäfer]

On Fri, Jun 08, 2012 at 08:51:09PM +0530, siddharth saxena wrote:
> Hi
> 
> Memcpy is both- a system call as well as a user library function.
> Implementation differs

Can you give me an example of memcpy being implemented as a syscall?

Thanks,
Jonathan Neusch?fer

is memcpy a system call?

[Bernd Petrovitsch]

Hi!

On Fre, 2012-06-08 at 20:51 +0530, siddharth saxena wrote:
[...]
> Memcpy is both- a system call as well as a user library function.
> Implementation differs

What makes you believe this?

	Bernd
-- 
Bernd Petrovitsch                  Email : bernd at petrovitsch.priv.at
                     LUGA : http://www.luga.at

is memcpy a system call?

[Jonathan Neuschäfer]

On Sat, Jun 09, 2012 at 12:11:36AM +0900, J.Hwan Kim wrote:
> Hi, everyone
> 
> Is memcpy a system call?
> 
> Thanks in advnace,
> 
> Best Regards,
> J.Hwna Kim

"strace" is a good tool to find out which system calls a program is
doing.

To answer your question, I don't think it makes much sense to implement
memcpy as a syscall, because entering kernel mode is usually relatively
expensive and I can't think of any kernel mode-only memcpy optimizations
(and optimizations are the only reason to do a user space memcpy in
kernel space I can think of).

HTH,
	Jonathan Neusch?fer

is memcpy a system call?

[Ezequiel Garcia]

On Fri, Jun 8, 2012 at 12:11 PM, J.Hwan Kim <frog1120@gmail.com> wrote:
> Hi, everyone
>
> Is memcpy a system call?
>

"Use the force, read the source"

uclibc:
http://git.uclibc.org/uClibc/tree/libc/string/generic/memcpy.c

glibc:
http://sourceware.org/git/?p=glibc.git;a=blob;f=string/memcpy.c;h=e167e85d7b31bda4e85ec7836631da2a15acf860;hb=c0da14cdda1fa552262ce3624156194eef43e973

Which means: No, memcpy (meaning the userspace function that gets
included by "string.h") is *not* a system call.

Hope this helps,
Ezequiel.