Messages in this thread Patch in this message | | | From | Stafford Horne <> | Subject | [PATCH 3/7] openrisc: restore call-saved regs on sigreturn | Date | Fri, 16 Sep 2016 23:43:01 +0900 |
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From: Jonas Bonn <jonas@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.
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 path.
Reported-by: Sebastian Macke <sebastian@macke.de> Signed-off-by: Jonas Bonn <jonas@southpole.se> Signed-off-by: Stafford Horne <shorne@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 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 -- 2.7.4
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