[Qemu-devel] [PATCH 04/24] target-arm: Log bad system register accesses with LOG_UNIMP

[Peter Maydell <peter.maydell@linaro.org>]

Log guest attempts to access unimplemented system registers via
the LOG_UNIMP reporting mechanism (for both the 32 bit and 64 bit
instruction sets). This is particularly useful for debugging
problems where the guest is trying to use a system register that
QEMU doesn't implement.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/translate-a64.c |  7 ++++++-
 target-arm/translate.c     | 13 +++++++++++++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
index a808a88..e0f6765 100644
--- a/target-arm/translate-a64.c
+++ b/target-arm/translate-a64.c
@@ -1121,7 +1121,12 @@ static void handle_sys(DisasContext *s, uint32_t insn, bool isread,
                                                crn, crm, op0, op1, op2));
 
     if (!ri) {
-        /* Unknown register */
+        /* Unknown register; this might be a guest error or a QEMU
+         * unimplemented feature.
+         */
+        qemu_log_mask(LOG_UNIMP, "%s access to unsupported AArch64 "
+                      "system register op0:%d op1:%d crn:%d crm:%d op2:%d\n",
+                      isread ? "read" : "write", op0, op1, crn, crm, op2);
         unallocated_encoding(s);
         return;
     }
diff --git a/target-arm/translate.c b/target-arm/translate.c
index 8d240e1..59a206d 100644
--- a/target-arm/translate.c
+++ b/target-arm/translate.c
@@ -6672,6 +6672,19 @@ static int disas_coproc_insn(CPUARMState * env, DisasContext *s, uint32_t insn)
         return 0;
     }
 
+    /* Unknown register; this might be a guest error or a QEMU
+     * unimplemented feature.
+     */
+    if (is64) {
+        qemu_log_mask(LOG_UNIMP, "%s access to unsupported AArch32 "
+                      "64 bit system register cp:%d opc1: %d crm:%d\n",
+                      isread ? "read" : "write", cpnum, opc1, crm);
+    } else {
+        qemu_log_mask(LOG_UNIMP, "%s access to unsupported AArch32 "
+                      "system register cp:%d opc1:%d crn:%d crm:%d opc2:%d\n",
+                      isread ? "read" : "write", cpnum, opc1, crn, crm, opc2);
+    }
+
     return 1;
 }
 
-- 
1.8.5