From 8264cb84fef7ea3a07c3011728bb426531aa86d8 Mon Sep 17 00:00:00 2001 From: Christophe Lyon Date: Mon, 18 Nov 2019 16:31:51 -0500 Subject: [PATCH] target/arm: Allow reading flags from FPSCR for M-profile rt==15 is a special case when reading the flags: it means the destination is APSR. This patch avoids rejecting vmrs apsr_nzcv, fpscr as illegal instruction. Backports commit cdc6896659b85f7ed8f7552850312e55170de0c5 from qemu --- qemu/target/arm/translate-vfp.inc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/qemu/target/arm/translate-vfp.inc.c b/qemu/target/arm/translate-vfp.inc.c index 23079834..0bf283bb 100644 --- a/qemu/target/arm/translate-vfp.inc.c +++ b/qemu/target/arm/translate-vfp.inc.c @@ -714,9 +714,10 @@ static bool trans_VMSR_VMRS(DisasContext *s, arg_VMSR_VMRS *a) if (arm_dc_feature(s, ARM_FEATURE_M)) { /* * The only M-profile VFP vmrs/vmsr sysreg is FPSCR. - * Writes to R15 are UNPREDICTABLE; we choose to undef. + * Accesses to R15 are UNPREDICTABLE; we choose to undef. + * (FPSCR -> r15 is a special case which writes to the PSR flags.) */ - if (a->rt == 15 || a->reg != ARM_VFP_FPSCR) { + if (a->rt == 15 && (!a->l || a->reg != ARM_VFP_FPSCR)) { return false; } }