From a468baff613be362efd93e18559cdc356f4208af Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Tue, 20 Feb 2018 22:18:46 -0500 Subject: [PATCH] target-arm: In cpsr_write() ignore mode switches from User mode The only case where we can attempt a cpsr_write() mode switch from User is from the gdbstub; all other cases are handled in the calling code (notably translate.c). Architecturally attempts to alter the mode bits from user mode are simply ignored (and not treated as a bad mode switch, which in v8 sets CPSR.IL). Make mode switches from User ignored in cpsr_write() as well, for consistency. Backports commit cb01d3912c8b000ed26d5fe95f6c194b3e3ba7a6 from qemu --- qemu/target-arm/helper.c | 1 + 1 file changed, 1 insertion(+) diff --git a/qemu/target-arm/helper.c b/qemu/target-arm/helper.c index a6d6b8d6..f5e6c0fb 100644 --- a/qemu/target-arm/helper.c +++ b/qemu/target-arm/helper.c @@ -4619,6 +4619,7 @@ void cpsr_write(CPUARMState *env, uint32_t val, uint32_t mask, env->daif |= val & CPSR_AIF & mask; if (write_type != CPSRWriteRaw && + (env->uncached_cpsr & CPSR_M) != CPSR_USER && ((env->uncached_cpsr ^ val) & mask & CPSR_M)) { if (bad_mode_switch(env, val & CPSR_M)) { /* Attempt to switch to an invalid mode: this is UNPREDICTABLE.