[Qemu-devel] [PATCH 02/18] armv7m: Undo armv7m.hack

[Michael Davidsaver <mdavidsaver@gmail.com>]

Add CPU unassigned access handler in place of special
MemoryRegion to catch exception returns.

Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
---
 hw/arm/armv7m.c  |  8 --------
 target-arm/cpu.c | 18 ++++++++++++++++++
 2 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
index a80d2ad..68146de 100644
--- a/hw/arm/armv7m.c
+++ b/hw/arm/armv7m.c
@@ -176,7 +176,6 @@ DeviceState *armv7m_init(MemoryRegion *system_memory, int mem_size, int num_irq,
     uint64_t entry;
     uint64_t lowaddr;
     int big_endian;
-    MemoryRegion *hack = g_new(MemoryRegion, 1);
 
     if (cpu_model == NULL) {
 	cpu_model = "cortex-m3";
@@ -221,13 +220,6 @@ DeviceState *armv7m_init(MemoryRegion *system_memory, int mem_size, int num_irq,
         }
     }
 
-    /* Hack to map an additional page of ram at the top of the address
-       space.  This stops qemu complaining about executing code outside RAM
-       when returning from an exception.  */
-    memory_region_init_ram(hack, NULL, "armv7m.hack", 0x1000, &error_fatal);
-    vmstate_register_ram_global(hack);
-    memory_region_add_subregion(system_memory, 0xfffff000, hack);
-
     qemu_register_reset(armv7m_reset, cpu);
     return nvic;
 }
diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 30739fc..be026bc 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -280,6 +280,23 @@ bool arm_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
 }
 
 #if !defined(CONFIG_USER_ONLY) || !defined(TARGET_AARCH64)
+static void arm_v7m_unassigned_access(CPUState *cpu, hwaddr addr,
+                                      bool is_write, bool is_exec, int opaque,
+                                      unsigned size)
+{
+    ARMCPU *arm = ARM_CPU(cpu);
+    CPUARMState *env = &arm->env;
+
+    if (env->v7m.exception != 0 && addr >= 0xfffffff0 && !is_write) {
+        cpu->exception_index = EXCP_EXCEPTION_EXIT;
+        cpu_loop_exit(cpu);
+    } else {
+        /* TODO, signal some *Fault? */
+        cpu_abort(cpu, "Trying to access outside RAM or ROM at 0x"
+                  TARGET_FMT_plx "\n", addr);
+    }
+}
+
 static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
 {
     CPUClass *cc = CPU_GET_CLASS(cs);
@@ -909,6 +926,7 @@ static void arm_v7m_class_init(ObjectClass *oc, void *data)
     cc->do_interrupt = arm_v7m_cpu_do_interrupt;
 #endif
 
+    cc->do_unassigned_access = arm_v7m_unassigned_access;
     cc->cpu_exec_interrupt = arm_v7m_cpu_exec_interrupt;
 }
 
-- 
2.1.4