Re: [PATCH 01/23] all: syscall wrappers: add documentation

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Wed, May 25, 2016 at 12:30:17PM -0700, David Miller wrote:
> From: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>
> Date: Tue, 24 May 2016 03:04:30 +0300
> 
> > +To clear that top halves, automatic wrappers are introduced. They clear all
> > +required registers before passing control to regular syscall handler.
> 
> Why have one of these for every single compat system call, rather than
> simply clearing the top half of all of these registers unconditionally
> in the 32-bit system call trap before the system call is invoked?
> 
> That's what we do on sparc64.
> 
> And with that, you only need wrappers for the case where there needs
> to be proper sign extention of a 32-bit signed argument.

It was discussed as one of possible solutions. The downside of it is
that we cannot pass 64-bit types (like off_t) in single register.
The other downside is that we clear top halves for every single
syscall, and it looks excessive. So, from spark64 and s390 approaches
we choosed second.
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Kernel Newbies]     [Security]     [Netfilter]     [Bugtraq]     [Linux FS]     [Yosemite Forum]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Video 4 Linux]     [Device Mapper]     [Linux Resources]

  Powered by Linux