Re: [PATCH v2] arch: Reserve map_shadow_stack() syscall number for all architectures
Catalin Marinas <[email protected]>
| Newsgroups | gmane.linux.kernel.api,gmane.linux.kernel.cross-arch,gmane.linux.ports.alpha,gmane.linux.kernel,gmane.linux.ports.arm.kernel,gmane.linux.ports.ia64,gmane.linux.ports.mips,gmane.linux.ports.parisc,gmane.linux.ports.ppc64.devel,gmane.linux.ports.sh.devel,gmane.linux.ports.sparc,gmane.linux.kernel.perf.user |
|---|---|
| Message-ID | <ZR0S0QUoAbqTS/[email protected]> |
On Thu, Sep 14, 2023 at 06:58:03PM +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.
>
> Link: https://lore.kernel.org/lkml/20230515212255.GA562920-Fj+DGH1r1ZPdDInqDg1lI3xStJ4P+DSV@public.gmane.org/
> Link: https://lore.kernel.org/lkml/b402b80b-a7c6-4ef0-b977-c0f5f582b78a-GFdadSzt00ze9xe1eoZjHA@public.gmane.org/
>
> Signed-off-by: Sohil Mehta <[email protected]>
> ---
> v2:
> - Skip syscall table changes to tools/. They will be handled separetely by the
> perf folks.
> - Map Powerpc to sys_ni_syscall (Rick Edgecombe)
> ---
> arch/alpha/kernel/syscalls/syscall.tbl | 1 +
> arch/arm/tools/syscall.tbl | 1 +
> arch/arm64/include/asm/unistd.h | 2 +-
> arch/arm64/include/asm/unistd32.h | 2 ++
For arm64 (compat):
Acked-by: Catalin Marinas <[email protected]>