On Mon, Jan 21, 2019 at 6:08 PM Arnd Bergmann <arnd@xxxxxxxx> wrote:
On Mon, Jan 21, 2019 at 9:19 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> 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)
