The SSR1 register can have bits set that don't match to bits in the MSR

register.  We would set the sc_ps member of struct sigcontext to SSR1
when entering a signal handler, and compare it to PSL_USER in sigreturn(2)
to make sure that the user code didn't set any bits it shouldn't set.
If non-MSR bits are set that comparison would fail and sigreturn(2) would
fail.  Fix this by initializing sc_ps to PSL_USER instead of taking its
value from SSR1.  On OpenBSD we always run processes with the same MSR
value.

ok deraadt@

diff --git a/sys/arch/powerpc64/powerpc64/machdep.c b/sys/arch/powerpc64/powerpc64/machdep.c
index cb1b89d..b846744 100644 (file)
--- a/sys/arch/powerpc64/powerpc64/machdep.c
+++ b/sys/arch/powerpc64/powerpc64/machdep.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: machdep.c,v 1.67 2021/01/09 13:14:02 kettenis Exp $   */
+/*     $OpenBSD: machdep.c,v 1.68 2021/04/15 07:28:37 kettenis Exp $   */
 
 /*
  * Copyright (c) 2020 Mark Kettenis <kettenis@openbsd.org>
@@ -933,7 +933,7 @@ sendsig(sig_t catcher, int sig, sigset_t mask, const siginfo_t *ksip)
        frame.sf_sc.sc_xer = tf->xer;
        frame.sf_sc.sc_ctr = tf->ctr;
        frame.sf_sc.sc_pc = tf->srr0;
-       frame.sf_sc.sc_ps = tf->srr1;
+       frame.sf_sc.sc_ps = PSL_USER;
        frame.sf_sc.sc_vrsave = tf->vrsave;
 
        /* Copy the saved FPU state into the frame if necessary. */