[LTP] [PATCH] syscalls/aarch64: Remove 32 bit only syscalls

[Arnd Bergmann <arnd@kernel.org>]

On Fri, Sep 3, 2021 at 6:22 AM Petr Vorel <pvorel@suse.cz> wrote:
>
> Hi all,
>
> > Hi Arnd,
>
> > On 9/2/2021 8:32 PM, Arnd Bergmann wrote:
>
> > > > > I am not 100% sure, how the syscall table for aarch64 is generated.
> > > > > There are also compat version for some of the 32 bit only 64 bit syscalls,
> > > > > but I think they are only available, when running an 32 bit arm application.
> > > The syscall table for aarch64 is generated from the kernel's
> > > include/uapi/asm-generic/unistd.h, which has a number of #ifdefs in
> > > it. A lot of these are disabled on aarch64 since they refer to older or
> > > 32-bit-only calls.
>
> > > https://marcin.juszkiewicz.com.pl/download/tables/syscalls.html has a table
> > > with the correct set of syscalls for each architecture, and scripts to generate
> > > them from both the old asm-generic/unistd.h method (now only still used on
> > > modern architectures) and the newer syscall.tbl format (used on older
> > > architectures)
> @Arnd: thanks a lot for this table and explanations! I would not expect this
> kind of error in kernel sources.

I don't see anything wrong in the kernel sources here, just a little misleading
when read by a human rather than a compiler.

> When I changed / reviewed syscall numbers for LTP, I usually compared with
> kernel and musl sources. I never noticed change, but now I see for
> clock_gettime64 it's in musl only for arm (arch/arm/bits/syscall.h.in), but in
> kernel it's not only for arm, but also for arm64:
> arm64/include/asm/unistd.h:30:#define __NR_compat_clock_gettime64       403

This is a kernel-internal definition that is used to build the 32-bit VDSO. The
file is not made available to user space applications.

The file you need to look at for arm64 is include/uapi/asm-generic/unistd.h.
As I said, that file has a lot of #ifdefs and other magic in it, but I suppose
we could come up with a script to process it with /usr/bin/unifdef to only
get the parts you are interested in. Ideally though we would just
convert it into the modern machine-readable syscall.tbl format.

        Arnd