[Qemu-devel] [V3 PATCH 2/2] monitor: QEMU Monitor Instruction Disassembly Incorrect for PowerPC LE Mode

[Tom Musta <tommusta@gmail.com>]

The monitor support for disassembling instructions does not honor the MSR[LE]
bit for PowerPC processors.

This change enhances the monitor_disas() routine by supporting a flag bit
for Little Endian mode.  Bit 16 is used since that bit was used in the
analagous guest disassembly routine target_disas().

Also, to be consistent with target_disas(), the disassembler bfd_mach field
can be passed in the flags argument.

Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Tom Musta <tommusta@gmail.com>
---

V2: Look specifically at bit 16 for LE.  Support machine configuration in flags.

V3: Changed documentation of 'flags' argument to simply refer to the target_disas
  description (per Peter Maydell's review).

The bug can be easily observed by dumping the first few instructions of an
interrupt vector (0x300 is the Data Storage Interrupt handler in PPC)

  (qemu) xp/8i 0x300
  0x0000000000000300:  .long 0x60
  0x0000000000000304:  lhzu    r18,-19843(r3)
  0x0000000000000308:  .long 0x60
  0x000000000000030c:  lhzu    r18,-20099(r2)
  0x0000000000000310:  lwz     r0,11769(0)
  0x0000000000000314:  lhzu    r23,8317(r2)
  0x0000000000000318:  .long 0x7813427c
  0x000000000000031c:  lbz     r0,19961(0)

With the patch applied, the disassembly now looks correct:

  (qemu) xp/8i 0x300
  0x0000000000000300:  nop
  0x0000000000000304:  mtsprg  2,r13
  0x0000000000000308:  nop
  0x000000000000030c:  mfsprg  r13,1
  0x0000000000000310:  std     r9,128(r13)
  0x0000000000000314:  mfspr   r9,896
  0x0000000000000318:  mr      r2,r2
  0x000000000000031c:  std     r10,136(r13)
 disas.c   |   14 ++++++++++++--
 monitor.c |    4 ++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/disas.c b/disas.c
index a427d18..f300102 100644
--- a/disas.c
+++ b/disas.c
@@ -445,6 +445,8 @@ monitor_fprintf(FILE *stream, const char *fmt, ...)
     return 0;
 }
 
+/* Disassembler for the monitor.  See target_disas for a description of 'flags'.
+ */
 void monitor_disas(Monitor *mon, CPUArchState *env,
                    target_ulong pc, int nb_insn, int is_physical, int flags)
 {
@@ -485,11 +487,19 @@ void monitor_disas(Monitor *mon, CPUArchState *env,
     s.info.mach = bfd_mach_sparc_v9b;
 #endif
 #elif defined(TARGET_PPC)
+    if (flags & 0xFFFF) {
+        /* If we have a precise definitions of the instructions set, use it */
+        s.info.mach = flags & 0xFFFF;
+    } else {
 #ifdef TARGET_PPC64
-    s.info.mach = bfd_mach_ppc64;
+        s.info.mach = bfd_mach_ppc64;
 #else
-    s.info.mach = bfd_mach_ppc;
+        s.info.mach = bfd_mach_ppc;
 #endif
+    }
+    if ((flags >> 16) & 1) {
+        s.info.endian = BFD_ENDIAN_LITTLE;
+    }
     print_insn = print_insn_ppc;
 #elif defined(TARGET_M68K)
     print_insn = print_insn_m68k;
diff --git a/monitor.c b/monitor.c
index 342e83b..3ae561b 100644
--- a/monitor.c
+++ b/monitor.c
@@ -1309,6 +1309,10 @@ static void memory_dump(Monitor *mon, int count, int format, int wsize,
             }
         }
 #endif
+#ifdef TARGET_PPC
+        flags = msr_le << 16;
+        flags |= env->bfd_mach;
+#endif
         monitor_disas(mon, env, addr, count, is_physical, flags);
         return;
     }
-- 
1.7.1