From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
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Subject: Re: [PATCH v2 29/29] y2038: add 64-bit time_t syscalls to all 32-bit architectures
Date: Mon, 21 Jan 2019 09:19:11 +0100 [thread overview]
Message-ID: <CAMuHMdXzQNEEDjWrmTph8Krovj1g2WhnBUaM=FvKB+J2fZqctA@mail.gmail.com> (raw)
In-Reply-To: <20190119142852.cntdihah4mpa3lgx@e5254000004ec.dyn.armlinux.org.uk>
Hi Russell,
On Sat, Jan 19, 2019 at 3:29 PM Russell King - ARM Linux admin
<linux@armlinux.org.uk> wrote:
> On Fri, Jan 18, 2019 at 11:53:25AM -0800, Andy Lutomirski wrote:
> > On Fri, Jan 18, 2019 at 11:33 AM Arnd Bergmann <arnd@arndb.de> wrote:
> > > On Fri, Jan 18, 2019 at 7:50 PM Andy Lutomirski <luto@kernel.org> wrote:
> > > > On Fri, Jan 18, 2019 at 8:25 AM Arnd Bergmann <arnd@arndb.de> wrote:
> > > > > - Once we get to 512, we clash with the x32 numbers (unless
> > > > > we remove x32 support first), and probably have to skip
> > > > > a few more. I also considered using the 512..547 space
> > > > > for 32-bit-only calls (which never clash with x32), but
> > > > > that also seems to add a bit of complexity.
> > > >
> > > > I have a patch that I'll send soon to make x32 use its own table. As
> > > > far as I'm concerned, 547 is *it*. 548 is just a normal number and is
> > > > not special. But let's please not reuse 512..547 for other purposes
> > > > on x86 variants -- that way lies even more confusion, IMO.
> > >
> > > Fair enough, the space for those numbers is cheap enough here.
> > > I take it you mean we also should not reuse that number space if
> > > we were to decide to remove x32 soon, but you are not worried
> > > about clashing with arch/alpha when everything else uses consistent
> > > numbers?
> > >
> >
> > I think we have two issues if we reuse those numbers for new syscalls.
> > First, I'd really like to see new syscalls be numbered consistently
> > everywhere, or at least on all x86 variants, and we can't on x32
> > because they mean something else. Perhaps more importantly, due to
> > what is arguably a rather severe bug, issuing a native x86_64 syscall
> > (x32 bit clear) with nr in the range 512..547 does *not* return
> > -ENOSYS on a kernel with x32 enabled. Instead it does something that
> > is somewhat arbitrary. With my patch applied, it will return -ENOSYS,
> > but old kernels will still exist, and this will break syscall probing.
> >
> > Can we perhaps just start the consistent numbers above 547 or maybe
> > block out 512..547 in the new regime?
>
> I don't think you gain much with that kind of scheme - it won't take
> very long before an architecture misses having a syscall added, and
> then someone else adds their own. Been there with ARM - I was keeping
> the syscall table in the same order as x86 for new syscalls, but now
Same for m68k, and probably other architectures.
> that others have been adding syscalls to the table since I converted
> ARM to the tabular form, that's now gone out the window.
>
> So, I think it's completely pointless to do what you're suggesting.
> We'll just end up with a big hole in the middle of the syscall table
> and then revert back to random numbering of syscalls thereafter again.
I believe the plan is to add future syscalls for all architectures in a
single commit, to keep everything in sync.
Regardless, I'm wondering what to do with the holes marked "room for
arch specific calls".
When is a syscall really arch-specific, and can it be added there, and
when does it turn out (later) that it isn't, breaking the
synchronization again?
The pkey syscalls may be a bad example, as AFAIU they can be implemented
on some architectures, but not on some others. Still, I had skipped them
when adding new syscalls to m68k.
Perhaps we should get rid of the notion of "arch-specific syscalls", and
reserve a slot everywhere anyway?
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2019-01-21 8:19 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-18 16:18 [PATCH v2 00/29] y2038: add time64 syscalls Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 01/29] ia64: add __NR_umount2 definition Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 02/29] ia64: add statx and io_pgetevents syscalls Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 03/29] ia64: assign syscall numbers for perf and seccomp Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 04/29] alpha: wire up io_pgetevents system call Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 05/29] alpha: update syscall macro definitions Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 06/29] ARM: add migrate_pages() system call Arnd Bergmann
2019-01-25 15:16 ` Catalin Marinas
2019-01-18 16:18 ` [PATCH v2 07/29] ARM: add kexec_file_load system call number Arnd Bergmann
2019-01-25 15:43 ` Catalin Marinas
2019-01-25 16:21 ` Russell King - ARM Linux admin
2019-01-18 16:18 ` [PATCH v2 08/29] m68k: assign syscall number for seccomp Arnd Bergmann
2019-01-21 8:55 ` Geert Uytterhoeven
2019-01-18 16:18 ` [PATCH v2 09/29] sh: remove duplicate unistd_32.h file Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 10/29] sh: add statx system call Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 11/29] sparc64: fix sparc_ipc type conversion Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 12/29] ipc: rename old-style shmctl/semctl/msgctl syscalls Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 13/29] arch: add split IPC system calls where needed Arnd Bergmann
2019-01-18 17:18 ` Gabriel Paubert
2019-01-18 19:30 ` Arnd Bergmann
2019-01-21 8:55 ` Geert Uytterhoeven
2019-01-21 11:57 ` Heiko Carstens
2019-01-18 16:18 ` [PATCH v2 14/29] arch: add pkey and rseq syscall numbers everywhere Arnd Bergmann
2019-01-21 8:55 ` Geert Uytterhoeven
2019-01-21 20:28 ` Arnd Bergmann
2019-01-21 11:59 ` Heiko Carstens
2019-01-18 16:18 ` [PATCH v2 15/29] alpha: add standard statfs64/fstatfs64 syscalls Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 16/29] alpha: add generic get{eg,eu,g,p,u,pp}id() syscalls Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 17/29] syscalls: remove obsolete __IGNORE_ macros Arnd Bergmann
2019-01-21 11:59 ` Heiko Carstens
2019-01-18 16:18 ` [PATCH v2 18/29] time: make adjtime compat handling available for 32 bit Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 19/29] time: Add struct __kernel_timex Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 20/29] time: fix sys_timer_settime prototype Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 21/29] sparc64: add custom adjtimex/clock_adjtime functions Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 22/29] timex: use __kernel_timex internally Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 23/29] timex: change syscalls to use struct __kernel_timex Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 24/29] x86/x32: use time64 versions of sigtimedwait and recvmmsg Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 26/29] y2038: use time32 syscall names on 32-bit Arnd Bergmann
2019-01-21 8:07 ` Geert Uytterhoeven
2019-01-21 8:56 ` Geert Uytterhoeven
2019-01-18 16:18 ` [PATCH v2 27/29] y2038: remove struct definition redirects Arnd Bergmann
2019-01-18 16:18 ` [PATCH v2 28/29] y2038: rename old time and utime syscalls Arnd Bergmann
2019-01-21 8:56 ` Geert Uytterhoeven
2019-01-21 12:15 ` Heiko Carstens
2019-01-18 16:18 ` [PATCH v2 29/29] y2038: add 64-bit time_t syscalls to all 32-bit architectures Arnd Bergmann
2019-01-18 18:50 ` Andy Lutomirski
2019-01-18 19:33 ` Arnd Bergmann
2019-01-18 19:53 ` Andy Lutomirski
2019-01-18 20:44 ` Arnd Bergmann
2019-01-19 14:28 ` Russell King - ARM Linux admin
2019-01-21 8:19 ` Geert Uytterhoeven [this message]
2019-01-21 17:08 ` Arnd Bergmann
2019-01-21 20:40 ` Arnd Bergmann
2019-01-21 8:56 ` Geert Uytterhoeven
2019-01-21 12:19 ` Heiko Carstens
2019-01-21 16:31 ` Arnd Bergmann
2019-01-25 15:55 ` Catalin Marinas
2019-01-18 16:57 ` [PATCH v2 00/29] y2038: add time64 syscalls Dennis Clarke
2019-01-18 17:14 ` Arnd Bergmann
2019-01-18 17:19 ` Dennis Clarke
2019-01-18 17:45 ` James Bottomley
[not found] ` <20190118161835.2259170-26-arnd@arndb.de>
2019-01-25 15:47 ` [PATCH v2 25/29] y2038: syscalls: rename y2038 compat syscalls Catalin Marinas
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