[RFC PATCH 09/13] cpus: Add const-qualified CPU environment accessors

Introduce const-qualified variants of cpu_env() and
env_archcpu(), to safely access CPU architecture
state when it should not be modified.

Signed-off-by: Philippe Mathieu-Daudé <[email protected]>
---
 include/exec/cpu-common.h | 11 +++++++++++
 include/hw/core/cpu.h     |  6 ++++++
 2 files changed, 17 insertions(+)

diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 6594f7fa1be..f3a3799f451 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -79,6 +79,17 @@ static inline bool cpu_loop_exit_requested(const CPUState *cpu)
 }
 #endif /* CONFIG_TCG */
 
+/**
+ * env_archcpu_const(env)
+ * @env: The architecture environment (const).
+ *
+ * Return the const ArchCPU associated with the environment.
+ */
+static inline const ArchCPU *env_archcpu_const(const CPUArchState *env)
+{
+    return (const void *)env - sizeof(CPUState);
+}
+
 /**
  * env_archcpu(env)
  * @env: The architecture environment
diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index 81af7b9ee1a..59f777f3f15 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -594,6 +594,12 @@ struct CPUState {
 QEMU_BUILD_BUG_ON(offsetof(CPUState, neg) !=
                   sizeof(CPUState) - sizeof(CPUNegativeOffsetState));
 
+static inline const CPUArchState *cpu_env_const(const CPUState *cpu)
+{
+    /* We validate that CPUArchState follows CPUState in cpu-target.c */
+    return (const CPUArchState *)(cpu + 1);
+}
+
 static inline CPUArchState *cpu_env(CPUState *cpu)
 {
     /* We validate that CPUArchState follows CPUState in cpu-target.c */
-- 
2.53.0