x86/shstk: Add ARCH_SHSTK_STATUS

CRIU and GDB need to get the current shadow stack and WRSS enablement
status. This information is already available via /proc/pid/status, but
this is inconvenient for CRIU because it involves parsing the text output
in an area of the code where this is difficult. Provide a status
arch_prctl(), ARCH_SHSTK_STATUS for retrieving the status. Have arg2 be a
userspace address, and make the new arch_prctl simply copy the features
out to userspace.

Suggested-by: Mike Rapoport <rppt@kernel.org>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Tested-by: Pengfei Xu <pengfei.xu@intel.com>
Tested-by: John Allen <john.allen@amd.com>
Tested-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/all/20230613001108.3040476-43-rick.p.edgecombe%40intel.com

1 files changed, 1 insertions, 1 deletions

diff --git a/arch/x86/include/asm/shstk.h b/arch/x86/include/asm/shstk.h
index ecb23a8ca47d..42fee8959df7 100644
--- a/arch/x86/include/asm/shstk.h
+++ b/arch/x86/include/asm/shstk.h
@@ -14,7 +14,7 @@ struct thread_shstk {
 	u64	size;
 };
 
-long shstk_prctl(struct task_struct *task, int option, unsigned long features);
+long shstk_prctl(struct task_struct *task, int option, unsigned long arg2);
 void reset_thread_features(void);
 unsigned long shstk_alloc_thread_stack(struct task_struct *p, unsigned long clone_flags,
 				       unsigned long stack_size);