[Mesa-dev] [PATCH 2/2] gallium/util: Android backtrace support

[Stefan Schake]

We can't use any of the existing implementations in u_debug_stack.
Android technically has libunwind, but it's been modified to the point
where it no longer compiles with the Mesa usage. The library is also
not meant to be referenced by vendor libraries. The officially sanctioned
way of obtaining backtraces is through the Android own libbacktrace, a
C++ library. Access it through a separate C++ source file on Android only.

Signed-off-by: Stefan Schake <stschake at gmail.com>
---
 src/gallium/auxiliary/Android.mk                   |   3 +-
 .../auxiliary/util/u_debug_stack_android.cpp       | 111 +++++++++++++++++++++
 src/gallium/targets/dri/Android.mk                 |   1 +
 3 files changed, 114 insertions(+), 1 deletion(-)
 create mode 100644 src/gallium/auxiliary/util/u_debug_stack_android.cpp

diff --git a/src/gallium/auxiliary/Android.mk b/src/gallium/auxiliary/Android.mk
index 2693838..acd243b 100644
--- a/src/gallium/auxiliary/Android.mk
+++ b/src/gallium/auxiliary/Android.mk
@@ -32,7 +32,8 @@ LOCAL_SRC_FILES := \
 	$(C_SOURCES) \
 	$(NIR_SOURCES) \
 	$(RENDERONLY_SOURCES) \
-	$(VL_STUB_SOURCES)
+	$(VL_STUB_SOURCES) \
+	util/u_debug_stack_android.cpp
 
 LOCAL_C_INCLUDES := \
 	$(GALLIUM_TOP)/auxiliary/util
diff --git a/src/gallium/auxiliary/util/u_debug_stack_android.cpp b/src/gallium/auxiliary/util/u_debug_stack_android.cpp
new file mode 100644
index 0000000..b3d56ae
--- /dev/null
+++ b/src/gallium/auxiliary/util/u_debug_stack_android.cpp
@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2018 Stefan Schake <stschake at gmail.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <backtrace/Backtrace.h>
+
+#include "u_debug.h"
+#include "u_debug_stack.h"
+#include "util/hash_table.h"
+#include "os/os_thread.h"
+
+static hash_table *backtrace_table;
+static mtx_t table_mutex = _MTX_INITIALIZER_NP;
+
+void
+debug_backtrace_capture(debug_stack_frame *mesa_backtrace,
+                        unsigned start_frame,
+                        unsigned nr_frames)
+{
+   hash_entry *backtrace_entry;
+   Backtrace *backtrace;
+   pid_t tid = gettid();
+
+   if (!nr_frames)
+      return;
+
+   /* We keep an Android Backtrace handler around for each thread */
+   mtx_lock(&table_mutex);
+   if (!backtrace_table)
+      backtrace_table = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
+                                                _mesa_key_pointer_equal);
+
+   backtrace_entry = _mesa_hash_table_search(backtrace_table, (void*) tid);
+   if (!backtrace_entry) {
+      backtrace = Backtrace::Create(getpid(), tid);
+      _mesa_hash_table_insert(backtrace_table, (void*) tid, backtrace);
+   } else {
+      backtrace = (Backtrace *) backtrace_entry->data;
+   }
+   mtx_unlock(&table_mutex);
+
+   /* Add one to exclude this call. Unwind already ignores itself. */
+   backtrace->Unwind(start_frame + 1);
+
+   /* Store the Backtrace handler in the first mesa frame for reference.
+    * Unwind will generally return less frames than nr_frames specified
+    * but we have no good way of storing the real count otherwise.
+    * The Backtrace handler only stores the results until the next Unwind,
+    * but that is how u_debug_stack is used anyway.
+    */
+   mesa_backtrace->function = backtrace;
+}
+
+void
+debug_backtrace_dump(const debug_stack_frame *mesa_backtrace,
+                     unsigned nr_frames)
+{
+   Backtrace *backtrace = (Backtrace *) mesa_backtrace->function;
+   size_t i;
+
+   if (!nr_frames)
+      return;
+
+   if (nr_frames > backtrace->NumFrames())
+      nr_frames = backtrace->NumFrames();
+   for (i = 0; i < nr_frames; i++) {
+      /* There is no prescribed format and this isn't interpreted further,
+       * so we simply use the default Android format.
+       */
+      const std::string& frame_line = backtrace->FormatFrameData(i);
+      debug_printf("%s\n", frame_line.c_str());
+   }
+}
+
+void
+debug_backtrace_print(FILE *f,
+                      const debug_stack_frame *mesa_backtrace,
+                      unsigned nr_frames)
+{
+   Backtrace *backtrace = (Backtrace *) mesa_backtrace->function;
+   size_t i;
+
+   if (!nr_frames)
+      return;
+
+   if (nr_frames > backtrace->NumFrames())
+      nr_frames = backtrace->NumFrames();
+   for (i = 0; i < nr_frames; i++) {
+      const std::string& frame_line = backtrace->FormatFrameData(i);
+      fprintf(f, "%s\n", frame_line.c_str());
+   }
+}
diff --git a/src/gallium/targets/dri/Android.mk b/src/gallium/targets/dri/Android.mk
index 5a3fda6..9c43fa1 100644
--- a/src/gallium/targets/dri/Android.mk
+++ b/src/gallium/targets/dri/Android.mk
@@ -40,6 +40,7 @@ LOCAL_LDFLAGS := \
 	-Wl,--undefined-version
 
 LOCAL_SHARED_LIBRARIES := \
+	libbacktrace \
 	libdl \
 	libglapi \
 	libexpat \
-- 
2.7.4