hw/misc/grlib_ahb_apb_pnp: Avoid crash when writing to PnP registers

Guests can crash QEMU when writting to PnP registers:

  $ echo 'writeb 0x800ff042 69' | qemu-system-sparc -M leon3_generic -S -bios /etc/magic -qtest stdio
  [I 1571938309.932255] OPENED
  [R +0.063474] writeb 0x800ff042 69
  Segmentation fault (core dumped)

  (gdb) bt
  #0  0x0000000000000000 in  ()
  thesofproject#1  0x0000555f4bcdf0bc in memory_region_write_with_attrs_accessor (mr=0x555f4d7be8c0, addr=66, value=0x7fff07d00f08, size=1, shift=0, mask=255, attrs=...) at memory.c:503
  thesofproject#2  0x0000555f4bcdf185 in access_with_adjusted_size (addr=66, value=0x7fff07d00f08, size=1, access_size_min=1, access_size_max=4, access_fn=0x555f4bcdeff4 <memory_region_write_with_attrs_accessor>, mr=0x555f4d7be8c0, attrs=...) at memory.c:539
  thesofproject#3  0x0000555f4bce2243 in memory_region_dispatch_write (mr=0x555f4d7be8c0, addr=66, data=69, op=MO_8, attrs=...) at memory.c:1489
  thesofproject#4  0x0000555f4bc80b20 in flatview_write_continue (fv=0x555f4d92c400, addr=2148528194, attrs=..., buf=0x7fff07d01120 "E", len=1, addr1=66, l=1, mr=0x555f4d7be8c0) at exec.c:3161
  thesofproject#5  0x0000555f4bc80c65 in flatview_write (fv=0x555f4d92c400, addr=2148528194, attrs=..., buf=0x7fff07d01120 "E", len=1) at exec.c:3201
  thesofproject#6  0x0000555f4bc80fb0 in address_space_write (as=0x555f4d7aa460, addr=2148528194, attrs=..., buf=0x7fff07d01120 "E", len=1) at exec.c:3291
  thesofproject#7  0x0000555f4bc8101d in address_space_rw (as=0x555f4d7aa460, addr=2148528194, attrs=..., buf=0x7fff07d01120 "E", len=1, is_write=true) at exec.c:3301
  thesofproject#8  0x0000555f4bcdb388 in qtest_process_command (chr=0x555f4c2ed7e0 <qtest_chr>, words=0x555f4db0c5d0) at qtest.c:432

Instead of crashing, log the access as unimplemented.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: KONRAD Frederic <frederic.konrad@adacore.com>
Message-Id: <20191025110114.27091-2-philmd@redhat.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

hw/misc/grlib_ahb_apb_pnp.c

@@ -22,6 +22,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/log.h"
 #include "hw/sysbus.h"
 #include "hw/misc/grlib_ahb_apb_pnp.h"
 
@@ -231,8 +232,15 @@ static uint64_t grlib_apb_pnp_read(void *opaque, hwaddr offset, unsigned size)
     return apb_pnp->regs[offset >> 2];
 }
 
+static void grlib_apb_pnp_write(void *opaque, hwaddr addr,
+                                uint64_t val, unsigned size)
+{
+    qemu_log_mask(LOG_UNIMP, "%s not implemented\n", __func__);
+}
+
 static const MemoryRegionOps grlib_apb_pnp_ops = {
     .read       = grlib_apb_pnp_read,
+    .write      = grlib_apb_pnp_write,
     .endianness = DEVICE_BIG_ENDIAN,
 };