Re: [PATCH v2 29/29] y2038: add 64-bit time_t syscalls to all 32-bit architectures

Arnd Bergmann
2019-01-21T20:40:01Z

On Mon, Jan 21, 2019 at 6:08 PM Arnd Bergmann <arnd@arndb.de> wrote:
> On Mon, Jan 21, 2019 at 9:19 AM Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > 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?
>
> We've had a bit of that already, with cacheflush(), which exists on
> a couple of architectures, including some that use the first
> 'arch specific' slot (244) of the asm-generic table. I think this
> will be rare enough that we can figure out a solution when we
> get there.
>
> > 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?
>
> I don't mind calling the hole something else if that helps. Out of
> principle I would already assume that anything we add for x86
> or the generic table should be added everywhere, but we can
> make it broader than that.

Applying this fixup below,

ARnd

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl
b/arch/x86/entry/syscalls/syscall_32.tbl
index d9c2d2eea044..955ab6a3b61f 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -398,7 +398,7 @@
384 i386 arch_prctl sys_arch_prctl
__ia32_compat_sys_arch_prctl
385 i386 io_pgetevents sys_io_pgetevents_time32
__ia32_compat_sys_io_pgetevents
386 i386 rseq sys_rseq
__ia32_sys_rseq
-# room for arch specific syscalls
+# don't use numbers 387 through 392, add new calls at the end
393 i386 semget sys_semget
__ia32_sys_semget
394 i386 semctl sys_semctl
__ia32_compat_sys_semctl
395 i386 shmget sys_shmget
__ia32_sys_shmget
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl
b/arch/x86/entry/syscalls/syscall_64.tbl
index 43a622aec07e..2ae92fddb6d5 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -343,6 +343,8 @@
332 common statx __x64_sys_statx
333 common io_pgetevents __x64_sys_io_pgetevents
334 common rseq __x64_sys_rseq
+# don't use numbers 387 through 423, add new calls after the last
+# 'common' entry

#
# x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/uapi/asm-generic/unistd.h
b/include/uapi/asm-generic/unistd.h
index 53831e4a4c86..acf9a07ab2ff 100644
--- a/include/uapi/asm-generic/unistd.h
+++ b/include/uapi/asm-generic/unistd.h
@@ -740,7 +740,7 @@ __SC_COMP_3264(__NR_io_pgetevents,
sys_io_pgetevents_time32, sys_io_pgetevents,
__SYSCALL(__NR_rseq, sys_rseq)
#define __NR_kexec_file_load 294
__SYSCALL(__NR_kexec_file_load, sys_kexec_file_load)
-/* 295 through 402 are unassigned to sync up with generic numbers */
+/* 295 through 402 are unassigned to sync up with generic numbers, don't use */
#if __BITS_PER_LONG = 32
#define __NR_clock_gettime64 403
__SYSCALL(__NR_clock_gettime64, sys_clock_gettime)