[Qemu-devel] [RFC 11/14] Print bbvec stats on 'magic' exceptions

[Christopher Covington <cov@codeaurora.org>]

This is necessary because we need a way to differentiate between
instructions executed in a PID by the benchmark we care about and those
executed by CRIU.

Written by Aaron Lindsay.

Signed-off-by: Christopher Covington <cov@codeaurora.org>
---
 bbv_profiler.c          | 15 +++++++++++++++
 bbv_profiler.h          |  1 +
 target-arm/helper-a64.c | 10 ++++++++++
 target-arm/helper.c     | 12 ++++++++++++
 4 files changed, 38 insertions(+)

diff --git a/bbv_profiler.c b/bbv_profiler.c
index 51e8060..66984b2 100644
--- a/bbv_profiler.c
+++ b/bbv_profiler.c
@@ -19,6 +19,12 @@
 #include <assert.h>
 #include "bbv_profiler.h"
 
+/* Magic number, which is set as bits 16-31 of the target of a branch which
+ * causes an exception to send a signal to the plugin.
+ */
+#define BBV_MAGIC_NUM 0xdead
+#define BBV_PRINT_STATS 0x0
+
 static BasicBlockTraceHandle trace = NULL;
 static uint32_t mode = 0;
 static uint64_t pid = 0;
@@ -75,3 +81,12 @@ void bb_context_check_pid(uint64_t IC, uint64_t new_pid)
 		bbvec_pid_change(trace, new_pid, IC);
 	}
 }
+
+/* Check if the bbv plugin is being signaled to do something by an exception */
+void bb_check_exception(uint64_t pc) {
+	if (((pc >> 16) & 0xffff) == BBV_MAGIC_NUM) {
+		uint16_t value = pc & 0xffff;
+		if (value == BBV_PRINT_STATS)
+			bbvec_print_stats(trace);
+	}
+}
diff --git a/bbv_profiler.h b/bbv_profiler.h
index 26dfa1f..b922451 100644
--- a/bbv_profiler.h
+++ b/bbv_profiler.h
@@ -31,5 +31,6 @@ int bbtrace_initialized(void);
 void bb_process(uint64_t PC, uint64_t IC);
 void bb_context_check_mode(uint64_t IC, uint32_t mode);
 void bb_context_check_pid(uint64_t IC, uint64_t tpid);
+void bb_check_exception(uint64_t pc);
 
 #endif
diff --git a/target-arm/helper-a64.c b/target-arm/helper-a64.c
index e647b90..95eb096 100644
--- a/target-arm/helper-a64.c
+++ b/target-arm/helper-a64.c
@@ -27,6 +27,10 @@
 #include "qemu/crc32c.h"
 #include <zlib.h> /* For crc32 */
 
+#ifdef CONFIG_BBVEC
+#include "bbv_profiler.h"
+#endif // CONFIG_BBVEC
+
 /* C2.4.7 Multiply and divide */
 /* special cases for 0 and LLONG_MIN are mandated by the standard */
 uint64_t HELPER(udiv64)(uint64_t num, uint64_t den)
@@ -470,6 +474,12 @@ void aarch64_cpu_do_interrupt(CPUState *cs)
     uint64_t mask;
 #endif
 
+#ifdef CONFIG_BBVEC
+    if (bbtrace_initialized()) {
+        bb_check_exception(is_a64(env) ? env->pc : env->regs[15]);
+    }
+#endif
+
     uint32_t syndrome =
       cs->exception_index == EXCP_ARMV8_HLT ?
         env->exception.syndrome & ~0xffff :
diff --git a/target-arm/helper.c b/target-arm/helper.c
index c1f4c47..297eb7c 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -4773,6 +4773,12 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
 
     arm_log_exception(cs->exception_index);
 
+#ifdef CONFIG_BBVEC
+    if (bbtrace_initialized()) {
+        bb_check_exception(env->regs[15]);
+    }
+#endif
+
     lr = 0xfffffff1;
     if (env->v7m.current_sp)
         lr |= 4;
@@ -5074,6 +5080,12 @@ void arm_cpu_do_interrupt(CPUState *cs)
         return;
     }
 
+#ifdef CONFIG_BBVEC
+    if (bbtrace_initialized()) {
+        bb_check_exception(env->regs[15]);
+    }
+#endif
+
     /* If this is a debug exception we must update the DBGDSCR.MOE bits */
     switch (env->exception.syndrome >> ARM_EL_EC_SHIFT) {
     case EC_BREAKPOINT:
-- 
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