From cc30dc441b44ad15f4adfb13d9a68cba6fa39a23 Mon Sep 17 00:00:00 2001 From: Richard Henderson Date: Mon, 24 Oct 2022 22:55:26 +1000 Subject: [PATCH] target/openrisc: Use cpu_unwind_state_data for mfspr Since we do not plan to exit, use cpu_unwind_state_data and extract exactly the data requested. This is a bug fix, in that we no longer clobber dflag. Consider: l.j L2 // branch l.mfspr r1, ppc // delay L1: boom L2: l.lwa r3, (r4) Here, dflag would be set by cpu_restore_state (because that is the current state of the cpu), but but not cleared by tb_stop on exiting the TB (because DisasContext has recorded the current value as zero). The next TB begins at L2 with dflag incorrectly set. If the load has a tlb miss, then the exception will be delivered as per a delay slot: with DSX set in the status register and PC decremented (delay slots restart by re-executing the branch). This will cause the return from interrupt to go to L1, and boom! Signed-off-by: Richard Henderson --- target/openrisc/sys_helper.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/target/openrisc/sys_helper.c b/target/openrisc/sys_helper.c index a3508e421d..dde2fa1623 100644 --- a/target/openrisc/sys_helper.c +++ b/target/openrisc/sys_helper.c @@ -199,6 +199,7 @@ target_ulong HELPER(mfspr)(CPUOpenRISCState *env, target_ulong rd, target_ulong spr) { #ifndef CONFIG_USER_ONLY + uint64_t data[TARGET_INSN_START_WORDS]; MachineState *ms = MACHINE(qdev_get_machine()); OpenRISCCPU *cpu = env_archcpu(env); CPUState *cs = env_cpu(env); @@ -232,14 +233,20 @@ target_ulong HELPER(mfspr)(CPUOpenRISCState *env, target_ulong rd, return env->evbar; case TO_SPR(0, 16): /* NPC (equals PC) */ - cpu_restore_state(cs, GETPC(), false); + if (cpu_unwind_state_data(cs, GETPC(), data)) { + return data[0]; + } return env->pc; case TO_SPR(0, 17): /* SR */ return cpu_get_sr(env); case TO_SPR(0, 18): /* PPC */ - cpu_restore_state(cs, GETPC(), false); + if (cpu_unwind_state_data(cs, GETPC(), data)) { + if (data[1] & 2) { + return data[0] - 4; + } + } return env->ppc; case TO_SPR(0, 32): /* EPCR */