arm: Clarify the logic of set_pc()

Until now, the set_pc logic was unclear, which raised questions about
whether it should be used directly, applying a value to PC or adding
additional checks, for example, set the Thumb bit in Arm cpu. Let's set
the set_pc logic for “Configure the PC, as was done in the ELF file”
and implement synchronize_with_tb hook for preserving PC to cpu_tb_exec.

Signed-off-by: Julia Suvorova <jusual@mail.ru>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20190129121817.7109-1-jusual@mail.ru
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 25 insertions, 1 deletions

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 8a9cd0900d..f00d450d0b 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -40,8 +40,31 @@
 static void arm_cpu_set_pc(CPUState *cs, vaddr value)
 {
     ARMCPU *cpu = ARM_CPU(cs);
+    CPUARMState *env = &cpu->env;
+
+    if (is_a64(env)) {
+        env->pc = value;
+        env->thumb = 0;
+    } else {
+        env->regs[15] = value & ~1;
+        env->thumb = value & 1;
+    }
+}
 
-    cpu->env.regs[15] = value;
+static void arm_cpu_synchronize_from_tb(CPUState *cs, TranslationBlock *tb)
+{
+    ARMCPU *cpu = ARM_CPU(cs);
+    CPUARMState *env = &cpu->env;
+
+    /*
+     * It's OK to look at env for the current mode here, because it's
+     * never possible for an AArch64 TB to chain to an AArch32 TB.
+     */
+    if (is_a64(env)) {
+        env->pc = tb->pc;
+    } else {
+        env->regs[15] = tb->pc;
+    }
 }
 
 static bool arm_cpu_has_work(CPUState *cs)
@@ -2099,6 +2122,7 @@ static void arm_cpu_class_init(ObjectClass *oc, void *data)
     cc->cpu_exec_interrupt = arm_cpu_exec_interrupt;
     cc->dump_state = arm_cpu_dump_state;
     cc->set_pc = arm_cpu_set_pc;
+    cc->synchronize_from_tb = arm_cpu_synchronize_from_tb;
     cc->gdb_read_register = arm_cpu_gdb_read_register;
     cc->gdb_write_register = arm_cpu_gdb_write_register;
 #ifdef CONFIG_USER_ONLY