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)