target/arm: Improve debug logging of AArch32 exception return

For AArch32, exception return happens through certain kinds
of CPSR write. We don't currently have any CPU_LOG_INT logging
of these events (unlike AArch64, where we log in the ERET
instruction). Add some suitable logging.

This will log exception returns like this:
Exception return from AArch32 hyp to usr PC 0x80100374

paralleling the existing logging in the exception_return
helper for AArch64 exception returns:
Exception return from AArch64 EL2 to AArch64 EL0 PC 0x8003045c
Exception return from AArch64 EL2 to AArch32 EL0 PC 0x8003045c

(Note that an AArch32 exception return can only be
AArch32->AArch32, never to AArch64.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20181012144235.19646-2-peter.maydell@linaro.org

1 files changed, 10 insertions, 0 deletions

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 6334d1ff71..56e4b18ddb 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6208,7 +6208,17 @@ void cpsr_write(CPUARMState *env, uint32_t val, uint32_t mask,
                 mask |= CPSR_IL;
                 val |= CPSR_IL;
             }
+            qemu_log_mask(LOG_GUEST_ERROR,
+                          "Illegal AArch32 mode switch attempt from %s to %s\n",
+                          aarch32_mode_name(env->uncached_cpsr),
+                          aarch32_mode_name(val));
         } else {
+            qemu_log_mask(CPU_LOG_INT, "%s %s to %s PC 0x%" PRIx32 "\n",
+                          write_type == CPSRWriteExceptionReturn ?
+                          "Exception return from AArch32" :
+                          "AArch32 mode switch from",
+                          aarch32_mode_name(env->uncached_cpsr),
+                          aarch32_mode_name(val), env->regs[15]);
             switch_mode(env, val & CPSR_M);
         }
     }