[XTENSA] Add support for the sa_restorer function
Supporting the sa_restorer function allows for better security
since the sigreturn system call doesn't need to be placed on
the stack, so the stack doesn't need to be executable. This
requires support from the c-library as it has to provide the
restorer function.
Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/arch/xtensa/kernel/signal.c b/arch/xtensa/kernel/signal.c
index 299be42..f2220b5 100644
--- a/arch/xtensa/kernel/signal.c
+++ b/arch/xtensa/kernel/signal.c
@@ -381,14 +381,19 @@
err |= setup_sigcontext(frame, regs);
err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
- /* Create sys_rt_sigreturn syscall in stack frame */
+ if (ka->sa.sa_flags & SA_RESTORER) {
+ ra = (unsigned long)ka->sa.sa_restorer;
+ } else {
- err |= gen_return_code(frame->retcode);
+ /* Create sys_rt_sigreturn syscall in stack frame */
- if (err) {
- goto give_sigsegv;
+ err |= gen_return_code(frame->retcode);
+
+ if (err) {
+ goto give_sigsegv;
+ }
+ ra = (unsigned long) frame->retcode;
}
-
/*
* Create signal handler execution context.
@@ -402,7 +407,6 @@
/* Set up a stack frame for a call4
* Note: PS.CALLINC is set to one by start_thread
*/
- ra = (unsigned long) frame->retcode;
regs->areg[4] = (((unsigned long) ra) & 0x3fffffff) | 0x40000000;
regs->areg[6] = (unsigned long) signal;
regs->areg[7] = (unsigned long) &frame->info;