Re: support for calling Linux syscalls directly

[Mike Frysinger <vapier at gentoo dot org>]

On Wednesday 30 January 2013 18:01:54 H. Peter Anvin wrote:
> I have had a number of discussions with people on this topic,
> especially given that syscall(3) is fundamentally flawed on a number
> of architectures, and that some architectures have been forced to use
> nonstandard signatures, complicating things.

could you elaborate on syscall(3) limitations ?  we used to have syscall#() 
inline funcs exported at various places (including the kernel's own headers), 
and those were a pain to maintain as well.  PIC issues readily come to mind.  
although, if we have explicit buy in from the kernel peeps to maintain it in 
all the various userland setups, it should be a much nicer ride.

> What I think makes sense is to create a library separate from glibc
> presumably called libinux containing the Linux-specific bits.  This
> libinux could ideally not just service glibc but also uClibc and
> Bionic (klibc itself is a little too "special" in that it doesn't have
> a dynamic linker at all.)
> 
> My intent was to revamp the infrastructure from klibc to create
> libinux, and eventually try to get it into the Linux kernel tree so
> that when new oddball system calls are added we can get everything in
> one place -- headers (with the recent uapi work), library, and of
> course the kernel itself.

will the kernel types get namespaced ?  or will it rely on the C library to 
provide the proper structures (according to relevant standards) ?  the problem 
we have currently with the network headers is they define the same structure 
name.  we don't want to have that be the starting point for a new lib, and it 
seems like it'd be real easy for that to become more of a problem.  another 
example is handling of bits that often share the enum/define names such as stat 
or fcntl or mmap.

> The "red line" for this library should be if it interacts with
> non-kernel data types in any kind of nontrivial way.

that's a good boundary to lay down.  i fear without rigorous control, it will 
be ripe for abuse by people to bypass glibc, or grow into an ugly monolithic 
mountain due to feature creep.
-mike

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