On Mon, 19 Sep 2016, Jonas Bonn wrote:

On 09/16/2016 04:43 PM, Stafford Horne wrote:
 From: Jonas Bonn <jo...@southpole.se>

 Return to userspace via _resume_userspace instead of via syscall return
 path for the rt_sigreturn syscall.

 I'll rework this comment more later, but this patch needs testing.

This whole patch was reworked later... what happened to that work? I recall it being posted for testing without feedback...

In any case, the patch comment needs cleaning up.

Hi Jonas,
When working through the changelogs to pull out these patches I didnt find anything more recent. However, I did only notice the commit message needed cleanup after posting the patch set. It was on my todo list to clean it up.

I will have another look for a later patch, I didnt find at first. But thanks for the info.


 Old comment from previous patch:

 The sigreturn syscall is more like a context switch than a function call;
 it entails a return from one context (the signal handler) to another
 (the process in question).  For a context switch like this there are
 effectively no call-saved regs that remain constant across the transition.

 This patch restores the call-saved regs from pt_regs before returning from
 the syscall, effectively restoring the context that the process had before
 being interrupted by the signal handler.  Restoring the call-saved regs
 in this way allows us to return to userspace via the usual syscall fast

 Reported-by: Sebastian Macke <sebast...@macke.de>
 Signed-off-by: Jonas Bonn <jo...@southpole.se>
 Signed-off-by: Stafford Horne <sho...@gmail.com>
   arch/openrisc/kernel/entry.S | 10 +++++++++-
   1 file changed, 9 insertions(+), 1 deletion(-)

 diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S
 index fec8bf9..572d223 100644
 --- a/arch/openrisc/kernel/entry.S
 +++ b/arch/openrisc/kernel/entry.S
 @@ -1101,8 +1101,16 @@ ENTRY(__sys_fork)
     l.addi     r3,r1,0

 -      l.j     _sys_rt_sigreturn
 +      l.jal   _sys_rt_sigreturn
         l.addi r3,r1,0
 +      l.sfne  r30,r0
 +      l.bnf   _no_syscall_trace
 +       l.nop
 +      l.jal   do_syscall_trace_leave
 +       l.addi r3,r1,0
 +      l.j     _resume_userspace
 +       l.nop

   /* This is a catch-all syscall for atomic instructions for the OpenRISC
    * The functions takes a variable number of parameters depending on

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