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>

3 files changed, 25 insertions, 19 deletions

diff --git a/target/arm/arm-powerctl.c b/target/arm/arm-powerctl.c
index 2b85693..f9de516 100644
--- a/target/arm/arm-powerctl.c
+++ b/target/arm/arm-powerctl.c
@@ -120,11 +120,8 @@ static void arm_set_cpu_on_async_work(CPUState *target_cpu_state,
 
     if (info->target_aa64) {
         target_cpu->env.xregs[0] = info->context_id;
-        target_cpu->env.thumb = false;
     } else {
         target_cpu->env.regs[0] = info->context_id;
-        target_cpu->env.thumb = info->entry & 1;
-        info->entry &= 0xfffffffe;
     }
 
     /* Start the new CPU at the requested address */
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index 8a9cd09..f00d450 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
diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index e9bc461..8653cec 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -480,20 +480,6 @@ static void aarch64_cpu_finalizefn(Object *obj)
 {
 }
 
-static void aarch64_cpu_set_pc(CPUState *cs, vaddr value)
-{
-    ARMCPU *cpu = ARM_CPU(cs);
-    /* 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.
-     * (Otherwise we would need to use synchronize_from_tb instead.)
-     */
-    if (is_a64(&cpu->env)) {
-        cpu->env.pc = value;
-    } else {
-        cpu->env.regs[15] = value;
-    }
-}
-
 static gchar *aarch64_gdb_arch_name(CPUState *cs)
 {
     return g_strdup("aarch64");
@@ -504,7 +490,6 @@ static void aarch64_cpu_class_init(ObjectClass *oc, void *data)
     CPUClass *cc = CPU_CLASS(oc);
 
     cc->cpu_exec_interrupt = arm_cpu_exec_interrupt;
-    cc->set_pc = aarch64_cpu_set_pc;
     cc->gdb_read_register = aarch64_cpu_gdb_read_register;
     cc->gdb_write_register = aarch64_cpu_gdb_write_register;
     cc->gdb_num_core_regs = 34;