add some trace apis

am/amtrace.h

@@ -1,7 +1,29 @@
 #ifndef __AMTRACE_H__
 #define __AMTRACE_H__
 
-void _trace_on();
-void _trace_off();
+struct _Trace {
+  uint8_t cpu;
+  uint8_t type;
+  uint16_t length;
+  char payload[];
+} __attribute__((packed));
+typedef struct _Trace _Trace;
+
+// ========================= trace components ========================
+
+#define _TRACE_IOE     0x00000001
+#define _TRACE_ASYE    0x00000002
+#define _TRACE_PTE     0x00000004
+#define _TRACE_MPE     0x00000008
+
+// =========================== trace points ==========================
+
+#define _TRACE_CALL    0x00010000
+#define _TRACE_RET     0x00020000
+#define _TRACE_FUNC    (_TRACE_CALL | _TRACE_RET)
+#define _TRACE_ALL     0xffffffff
+
+void _trace_on(uint32_t flags);
+void _trace_off(uint32_t flags);
 
 #endif

am/arch/x86-qemu/include/am-x86.h

@@ -8,7 +8,7 @@
 
 extern volatile uint32_t *lapic;
 extern int ncpu;
-extern volatile int trace_on;
+extern volatile uint32_t trace_flags;
 
 void lapic_eoi();
 void lapic_init();
@@ -60,4 +60,15 @@ void vec14();
 void vecsys();
 void irqall();
 
+static inline int traced() {
+#ifdef EXT
+  uint32_t flags = trace_flags;
+  if ( (flags & _TRACE_##EXT) && // the extension is being traced
+       1) {
+    return 1;
+  }
+#endif
+  return 0;
+}
+
 #endif

am/arch/x86-qemu/src/trace.c

@@ -1,11 +1,12 @@
 #include <am-x86.h>
 
-volatile int trace_on = 0;
+volatile uint32_t trace_flags = 0;
 
-void _trace_on() {
-  _atomic_xchg(&trace_on, 1);
+void _trace_on(uint32_t flags) {
+  // TODO: multiprocessor safety
+  trace_flags |= flags;
 }
 
-void _trace_off() {
-  _atomic_xchg(&trace_on, 0);
+void _trace_off(uint32_t flags) {
+  trace_flags &= ~flags;
 }

tests/vmtest/main.c

@@ -1,5 +1,6 @@
 #include <am.h>
 #include <amdev.h>
+#include <amtrace.h>
 #include <klib.h>
 
 _Context *uctx;
@@ -61,6 +62,7 @@ uint8_t code[] = {
 uint8_t kstk[4096];
 
 int main() {
+  _trace_on(_TRACE_ALL);
   st = (uintptr_t)_heap.start;
   _ioe_init();
   _asye_init(handler);