Re: [RFC][PATCH 1/3] powerpc: Don't force ENOSYS as error on syscall fail

In certain scenarios - e.g. seccomp filtering with ERRNO as default action -
the system call fails for other reasons than the syscall not being available.
The seccomp filter can be configured to store a user-defined error code on
return from a blacklisted syscall.

The RFC is this: are there currently any user-space scenarios where it is
required that the system call return ENOSYS as error code on failure, no matter
the circumstances? I don't want to break userspace requirements. I have not
added code to force this error code in situations different than
secure_computing failure, in order to keep overhead at a minimum.

Signed-off-by: Bogdan Purcareata <redacted>
---
  arch/powerpc/kernel/entry_32.S | 3 ++-
  arch/powerpc/kernel/entry_64.S | 2 +-
  2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 59848e5..52e48dd 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S

@@ -425,7 +425,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
  	b	1b
  #endif  /* CONFIG_44x */

-66:	li	r3,-ENOSYS
+66:
+#	li	r3,-ENOSYS
  	b	ret_from_syscall

  	.globl	ret_from_fork

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index e6bfe8e..80db02e 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S

@@ -269,7 +269,7 @@ syscall_dotrace:
  	b	.Lsyscall_dotrace_cont

  syscall_enosys:
-	li	r3,-ENOSYS
+#	li	r3,-ENOSYS
  	b	syscall_exit
  	
  syscall_exit_work: