Re: [PATCH v2] arch: Reserve map_shadow_stack() syscall number for all architectures
From: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Date: 2023-09-14 22:08:17
Also in:
linux-alpha, linux-arch, linux-m68k, linux-mips, linux-perf-users, linux-s390, linux-sh, linuxppc-dev, lkml, sparclinux
On Thu, 2023-09-14 at 18:58 +0000, Sohil Mehta wrote:
commit c35559f94ebc ("x86/shstk: Introduce map_shadow_stack syscall")
recently added support for map_shadow_stack() but it is limited to
x86
only for now. There is a possibility that other architectures
(namely,
arm64 and RISC-V), that are implementing equivalent support for
shadow
stacks, might need to add support for it.
Independent of that, reserving arch-specific syscall numbers in the
syscall tables of all architectures is good practice and would help
avoid future conflicts. map_shadow_stack() is marked as a conditional
syscall in sys_ni.c. Adding it to the syscall tables of other
architectures is harmless and would return ENOSYS when exercised.
Note, map_shadow_stack() was assigned #453 during the merge process
since #452 was taken by fchmodat2().
For Powerpc, map it to sys_ni_syscall() as is the norm for Powerpc
syscall tables.
For Alpha, map_shadow_stack() takes up #563 as Alpha still diverges
from
the common syscall numbering system in the other architectures.Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>