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openrisc: restore all regs on rt_sigreturn

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Fix signal handling for when signals are handled as the result of timers
or exceptions, previous code assumed syscalls. This was noticeable with X
crashing where it uses SIGALRM.

This patch restores all regs before returning to userspace via
_resume_userspace instead of via syscall return path.

The rt_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.

Reported-by: Sebastian Macke <sebastian@macke.de>
Signed-off-by: Jonas Bonn <jonas@southpole.se>
Tested-by: Guenter Roeck <linux@roeck-us.net>
[shorne@gmail.com: Updated comment better reflect change and issue]
Signed-off-by: Stafford Horne <shorne@gmail.com>
This commit is contained in:
Jonas Bonn 2013-09-23 12:04:20 +02:00 committed by Stafford Horne
parent f47706099b
commit c79902190f
1 changed files with 9 additions and 1 deletions
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arch/openrisc/kernel/entry.S
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@ -1101,8 +1101,16 @@ ENTRY(__sys_fork)
l.addi r3,r1,0
ENTRY(sys_rt_sigreturn)
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
_no_syscall_trace:
l.j _resume_userspace
l.nop
/* This is a catch-all syscall for atomic instructions for the OpenRISC 1000.
* The functions takes a variable number of parameters depending on which