On Wed, Aug 27, 2014 at 06:55:46AM +0100, AKASHI Takahiro wrote:
On 08/27/2014 02:51 AM, Will Deacon wrote:
On Fri, Aug 22, 2014 at 01:35:17AM +0100, AKASHI Takahiro wrote:
Oops, you're absolutely right. I didn't think of this case. syscall_trace_enter() should not return a syscallno directly, but always return -1 if syscallno < 0. (except when secure_computing() returns with -1) This also implies that tracehook_report_syscall() should also have a return value.
Will, is this fine with you?
Well, the first thing that jumps out at me is why this is being done completely differently for arm64 and arm. I thought adding the new ptrace requests would reconcile the differences?
I'm not sure what portion of my code you mentioned as "completely different", but
setting x0 to -ENOSYS is necessary because, otherwise, user-issued syscall(-1) will return a bogus value when audit tracing is on.
Please note that, on arm, not traced traced ------ ------ syscall(-1) aborted OOPs(BUG_ON) syscall(-3000) aborted aborted syscall(1000) ENOSYS ENOSYS
So, anyhow, its a bit difficult and meaningless to mimic these invalid cases.
I'm not suggesting we make ourselves bug-compatible with ARM. Instead, I'd rather see a series of patches getting the ARM code working correctly, before we go off doing something different for arm64.
branching a new label, syscall_trace_return_skip (see entry.S), after syscall_trace_enter() is necessary in order to avoid OOPS in audit_syscall_enter() as we discussed.
Did I make it clear?
Sure. So let's fix ARM, then look at the arm64 port after that. I really want to avoid divergence in this area.
Will