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s390x: fix clobbering of return values in swapcontext

master
Ariadne Conill 2024-08-07 19:04:45 -07:00
parent c1ecb0ea59
commit c468c50b7b
1 changed files with 6 additions and 4 deletions
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10
arch/s390x/swapcontext.S
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2018, 2020 Ariadne Conill <ariadne@dereferenced.org>
* Copyright (c) 2018, 2020, 2024 Ariadne Conill <ariadne@dereferenced.org>
*
* 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)