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

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Date:	Mon, 9 Feb 2015 07:55:14 +0000
From:	Bogdan Purcareata <bogdan.purcareata@...escale.com>
To:	<benh@...nel.crashing.org>, <paulus@...ba.org>,
	<linuxppc-dev@...ts.ozlabs.org>
CC:	<linux-kernel@...r.kernel.org>, <pmoore@...hat.com>,
	<strosake@...ux.vnet.ibm.com>,
	Bogdan Purcareata <bogdan.purcareata@...escale.com>
Subject: [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 <bogdan.purcareata@...escale.com>
---
 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:
-- 
2.1.4

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