From c468c50b7b2a778406b46bd9b554339990dd7df3 Mon Sep 17 00:00:00 2001 From: Ariadne Conill Date: Wed, 7 Aug 2024 19:04:45 -0700 Subject: [PATCH] s390x: fix clobbering of return values in swapcontext --- arch/s390x/swapcontext.S | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/arch/s390x/swapcontext.S b/arch/s390x/swapcontext.S index 21a9b5a..64113e1 100644 --- a/arch/s390x/swapcontext.S +++ b/arch/s390x/swapcontext.S @@ -1,5 +1,5 @@ /* - * Copyright (c) 2018, 2020 Ariadne Conill + * Copyright (c) 2018, 2020, 2024 Ariadne Conill * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above @@ -19,12 +19,14 @@ FUNC(libucontext_swapcontext) lgr %r1, %r2 /* use %r1 to save current context to */ lgr %r0, %r3 /* use %r0 for source context */ + la %r2, 0 /* zero out future return value */ + stam %a0, %a15, AREG_OFFSET(0)(%r1) /* store access registers */ stmg %r0, %r15, REG_OFFSET(0)(%r1) /* store general-purpose registers */ - lgr %r2, %r0 /* swap %r0 to %r2 (XXX: figure out why it hates loading from %r0) */ - lam %a2, %a15, AREG_OFFSET(2)(%r2) /* load access registers, but skip %a0 and %a1 which are for TLS */ - lmg %r0, %r15, REG_OFFSET(0)(%r2) /* load general-purpose registers */ + lgr %r5, %r0 /* copy %r0 to %r5 so that %r0 doesn't get clobbered */ + lam %a2, %a15, AREG_OFFSET(2)(%r5) /* load access registers, but skip %a0 and %a1 which are for TLS */ + lmg %r0, %r15, REG_OFFSET(0)(%r5) /* load general-purpose registers */ br %r14 /* return to new link register address */ END(libucontext_swapcontext)