Add support for tracing Java method entry/exit in emulator.

This is part of a larger change and depends on changes to the
kernel and the emulator tracing code.  The code used to work by
by writing to a "magic page" which the emulator would notice
because it watches every load and store.  But the emulator lost
the ability to watch every load and store with the latest update
to qemu.  So the new code sets up a memory-mapped page that the
emulator watches.  This is cleaner and more efficient anyway.

diff --git a/vm/Profile.c b/vm/Profile.c
index f7e6c17..6055580 100644 (file)
--- a/vm/Profile.c
+++ b/vm/Profile.c
@@ -29,10 +29,10 @@
 #include <sys/mman.h>
 #include <sched.h>
 #include <errno.h>
+#include <fcntl.h>
 
 #ifdef HAVE_ANDROID_OS
 # define UPDATE_MAGIC_PAGE      1
-# define MAGIC_PAGE_BASE_ADDR   0x08000000
 # ifndef PAGESIZE
 #  define PAGESIZE              4096
 # endif
@@ -177,13 +177,20 @@ bool dvmProfilingStartup(void)
      * We could key this off of the "ro.kernel.qemu" property, but there's
      * no real harm in doing this on a real device.
      */
-    gDvm.emulatorTracePage = mmap((void*) MAGIC_PAGE_BASE_ADDR,
-        PAGESIZE, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED|MAP_ANON, -1, 0);
-    if (gDvm.emulatorTracePage == MAP_FAILED) {
-        LOGE("Unable to mmap magic page (0x%08x)\n", MAGIC_PAGE_BASE_ADDR);
-        return false;
+    int fd = open("/dev/qemu_trace", O_RDWR);
+    if (fd < 0) {
+        LOGV("Unable to open /dev/qemu_trace\n");
+    } else {
+        gDvm.emulatorTracePage = mmap(0, PAGESIZE, PROT_READ|PROT_WRITE,
+                                      MAP_SHARED, fd, 0);
+        close(fd);
+        if (gDvm.emulatorTracePage == MAP_FAILED) {
+            LOGE("Unable to mmap /dev/qemu_trace\n");
+            gDvm.emulatorTracePage = NULL;
+        } else {
+            *(u4*) gDvm.emulatorTracePage = 0;
+        }
     }
-    *(u4*) gDvm.emulatorTracePage = 0;
 #else
     assert(gDvm.emulatorTracePage == NULL);
 #endif
@@ -639,7 +646,7 @@ void dvmEmitEmulatorTrace(const Method* method, int action)
         return;
     assert(method->insns != NULL);
 
-    u4* pMagic = ((u4*) MAGIC_PAGE_BASE_ADDR) +1;
+    u4* pMagic = (u4*) gDvm.emulatorTracePage;
 
     /*
      * The dexlist output shows the &DexCode.insns offset value, which
@@ -702,6 +709,10 @@ void dvmMethodTraceClassPrepEnd(void)
  */
 void dvmEmulatorTraceStart(void)
 {
+    /* If we could not map the emulator trace page, then do not enable tracing */
+    if (gDvm.emulatorTracePage == NULL)
+        return;
+
     updateActiveProfilers(1);
 
     /* in theory we should make this an atomic inc; in practice not important */
@@ -717,7 +728,7 @@ void dvmEmulatorTraceStop(void)
 {
     if (gDvm.emulatorTraceEnableCount == 0) {
         LOGE("ERROR: emulator tracing not enabled\n");
-        dvmAbort();
+        return;
     }
     updateActiveProfilers(-1);
     /* in theory we should make this an atomic inc; in practice not important */