[Qemu-devel] [PATCH v2] target-arm: Implement 'int' loglevel

[Qemu-devel] [PATCH v2] target-arm: Implement 'int' loglevel

[Peter Maydell]

The 'int' loglevel for recording interrupts and exceptions
requires support in the target-specific code. Implement
it for ARM. This improves debug logging in some situations
that were otherwise pretty opaque, such as when we fault
trying to execute at an exception vector address, which
would otherwise cause an infinite loop of taking exceptions
without any indication in the debug log of what was going on.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Changes v1->v2: added extra 'const' to excnames[] definition
as per rth review.

 target-arm/helper.c |   42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 4968391..6d9026d 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -1974,6 +1974,37 @@ static void do_v7m_exception_exit(CPUARMState *env)
        pointer.  */
 }
 
+/* Exception names for debug logging; note that not all of these
+ * precisely correspond to architectural exceptions.
+ */
+static const char * const excnames[] = {
+    [EXCP_UDEF] = "Undefined Instruction",
+    [EXCP_SWI] = "SVC",
+    [EXCP_PREFETCH_ABORT] = "Prefetch Abort",
+    [EXCP_DATA_ABORT] = "Data Abort",
+    [EXCP_IRQ] = "IRQ",
+    [EXCP_FIQ] = "FIQ",
+    [EXCP_BKPT] = "Breakpoint",
+    [EXCP_EXCEPTION_EXIT] = "QEMU v7M exception exit",
+    [EXCP_KERNEL_TRAP] = "QEMU intercept of kernel commpage",
+    [EXCP_STREX] = "QEMU intercept of STREX",
+};
+
+static inline void arm_log_exception(int idx)
+{
+    if (qemu_loglevel_mask(CPU_LOG_INT)) {
+        const char *exc = NULL;
+
+        if (idx >= 0 && idx < ARRAY_SIZE(excnames)) {
+            exc = excnames[idx];
+        }
+        if (!exc) {
+            exc = "unknown";
+        }
+        qemu_log_mask(CPU_LOG_INT, "Taking exception %d [%s]\n", idx, exc);
+    }
+}
+
 void arm_v7m_cpu_do_interrupt(CPUState *cs)
 {
     ARMCPU *cpu = ARM_CPU(cs);
@@ -1982,6 +2013,8 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
     uint32_t lr;
     uint32_t addr;
 
+    arm_log_exception(env->exception_index);
+
     lr = 0xfffffff1;
     if (env->v7m.current_sp)
         lr |= 4;
@@ -2011,6 +2044,7 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
             if (nr == 0xab) {
                 env->regs[15] += 2;
                 env->regs[0] = do_arm_semihosting(env);
+                qemu_log_mask(CPU_LOG_INT, "...handled as semihosting call\n");
                 return;
             }
         }
@@ -2064,6 +2098,8 @@ void arm_cpu_do_interrupt(CPUState *cs)
 
     assert(!IS_M(env));
 
+    arm_log_exception(env->exception_index);
+
     /* TODO: Vectored interrupt controller.  */
     switch (env->exception_index) {
     case EXCP_UDEF:
@@ -2091,6 +2127,7 @@ void arm_cpu_do_interrupt(CPUState *cs)
                     || (mask == 0xab && env->thumb))
                   && (env->uncached_cpsr & CPSR_M) != ARM_CPU_MODE_USR) {
                 env->regs[0] = do_arm_semihosting(env);
+                qemu_log_mask(CPU_LOG_INT, "...handled as semihosting call\n");
                 return;
             }
         }
@@ -2108,18 +2145,23 @@ void arm_cpu_do_interrupt(CPUState *cs)
                   && (env->uncached_cpsr & CPSR_M) != ARM_CPU_MODE_USR) {
                 env->regs[15] += 2;
                 env->regs[0] = do_arm_semihosting(env);
+                qemu_log_mask(CPU_LOG_INT, "...handled as semihosting call\n");
                 return;
             }
         }
         env->cp15.c5_insn = 2;
         /* Fall through to prefetch abort.  */
     case EXCP_PREFETCH_ABORT:
+        qemu_log_mask(CPU_LOG_INT, "...with IFSR 0x%x IFAR 0x%x\n",
+                      env->cp15.c5_insn, env->cp15.c6_insn);
         new_mode = ARM_CPU_MODE_ABT;
         addr = 0x0c;
         mask = CPSR_A | CPSR_I;
         offset = 4;
         break;
     case EXCP_DATA_ABORT:
+        qemu_log_mask(CPU_LOG_INT, "...with DFSR 0x%x DFAR 0x%x\n",
+                      env->cp15.c5_data, env->cp15.c6_data);
         new_mode = ARM_CPU_MODE_ABT;
         addr = 0x10;
         mask = CPSR_A | CPSR_I;
-- 
1.7.9.5

Re: [Qemu-devel] [PATCH v2] target-arm: Implement 'int' loglevel

[Richard Henderson]

On 08/05/2013 01:06 AM, Peter Maydell wrote:
> +        const char *exc = NULL;
> +
> +        if (idx >= 0 && idx < ARRAY_SIZE(excnames)) {
> +            exc = excnames[idx];
> +        }
> +        if (!exc) {
> +            exc = "unknown";
> +        }

Silly test for null here.

  const char *exc = "unknown";
  if (...) {
     exc = excnames[idx];
  }

Otherwise the patch looks good.


r~

Re: [Qemu-devel] [PATCH v2] target-arm: Implement 'int' loglevel

[Richard Henderson]

On 08/05/2013 01:06 AM, Peter Maydell wrote:
> +        const char *exc = NULL;
> +
> +        if (idx >= 0 && idx < ARRAY_SIZE(excnames)) {
> +            exc = excnames[idx];
> +        }
> +        if (!exc) {
> +            exc = "unknown";
> +        }

Gah.  Nevermind that last comment, I knew it was wrong the instant
after I pressed send.  Brain needs more coffee applied...


r~

Re: [Qemu-devel] [PATCH v2] target-arm: Implement 'int' loglevel

[Richard Henderson]

On 08/05/2013 01:06 AM, Peter Maydell wrote:
> The 'int' loglevel for recording interrupts and exceptions
> requires support in the target-specific code. Implement
> it for ARM. This improves debug logging in some situations
> that were otherwise pretty opaque, such as when we fault
> trying to execute at an exception vector address, which
> would otherwise cause an infinite loop of taking exceptions
> without any indication in the debug log of what was going on.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> Changes v1->v2: added extra 'const' to excnames[] definition
> as per rth review.
> 
>  target-arm/helper.c |   42 ++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 42 insertions(+)

Reviewed-by: Richard Henderson <rth@twiddle.net>


r~