armv7m: Replace armv7m.hack with unassigned_access handler

For v7m we need to catch attempts to execute from special
addresses at 0xfffffff0 and above. Previously we did this
with the aid of a hacky special purpose lump of memory
in the address space and a check in translate.c for whether
we were translating code at those addresses.

We can implement this more cleanly using a CPU
unassigned access handler which throws the exception
if the unassigned access is for one of the special addresses.

Signed-off-by: Michael Davidsaver <mdavidsaver@gmail.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 1484937883-1068-3-git-send-email-peter.maydell@linaro.org
[PMM:
 * drop the deletion of the "don't interrupt if PC is magic"
   code in arm_v7m_cpu_exec_interrupt() -- this is still
   required
 * don't generate an exception for unassigned accesses
   which aren't to the magic address -- although doing
   this is in theory correct in practice it will break
   currently working guests which rely on the RAZ/WI
   behaviour when they touch devices which we haven't
   modelled.
 * trigger EXCP_EXCEPTION_EXIT on is_exec, not !is_write
]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 0 insertions, 8 deletions

diff --git a/hw/arm/armv7m.c b/hw/arm/armv7m.c
index 49d30782c8..0c9ca7bfa0 100644
--- a/hw/arm/armv7m.c
+++ b/hw/arm/armv7m.c
@@ -180,7 +180,6 @@ 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";
@@ -225,13 +224,6 @@ 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;
 }