mesa: Make the android_stub be a set of non-installed shared libraries.

Previously, we included the stubs in our driver binaries, so they didn't
call the actual system libraries for these functions.  This was enough to
build-test the Android code in CI without even the NDK.

To make NDK-built Mesa drivers useful, we need to link against these
system libraries that aren't present in the NDK.  Split the symbols to
separate non-installed shared libraries and link against those, so that
when you drop the resulting .so in your /vendor/lib64/hw/, it just works
out.

Reviewed-by: Kristian H. Kristensen <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6805>

Author: anholt

src/android_stub/README.md

@@ -0,0 +1,5 @@
+The Android NDK doesn't come with enough of the platform libraries we
+need to build Mesa drivers out of tree, so android_stub has stub
+versions of those library that aren't installed which we link against,
+relying on the real libraries to be present when the Mesa driver is
+deployed.

src/android_stub/android_stub.cpp

@@ -0,0 +1,14 @@
+#include <backtrace/Backtrace.h>
+
+Backtrace*
+Backtrace::Create(pid_t pid, pid_t tid, BacktraceMap* map)
+{
+   return NULL;
+}
+
+std::string
+backtrace_map_t::Name() const
+{
+   return "";
+}
+

src/android_stub/backtrace_stub.cpp

@@ -0,0 +1,10 @@
+#include <cutils/properties.h>
+
+extern "C" {
+
+int property_get(const char* key, char* value, const char* default_value)
+{
+   return 0;
+}
+
+}

src/android_stub/cutils_stub.cpp

@@ -0,0 +1,10 @@
+#include <hardware/hardware.h>
+
+extern "C" {
+
+int hw_get_module(const char *id, const struct hw_module_t **module)
+{
+   return 0;
+}
+
+}

src/android_stub/hardware_stub.cpp

@@ -0,0 +1,15 @@
+#include <android/log.h>
+
+extern "C" {
+
+int __android_log_print(int prio, const char* tag, const char* fmt, ...)
+{
+   return 0;
+}
+
+int __android_log_vprint(int prio, const char* tag, const char* fmt, va_list ap)
+{
+   return 0;
+}
+
+}

src/android_stub/log_stub.cpp

@@ -1,12 +1,16 @@
 if with_android_stub
-  _libmesa_android_stub = static_library(
-    'mesa_android_stub',
-    files('android_stub.cpp'),
-    include_directories : inc_include,
-    gnu_symbol_visibility : 'hidden',
-  )
+  stub_libs = []
+
+  foreach lib : ['backtrace', 'cutils', 'hardware', 'log', 'sync']
+    stub_libs += shared_library(
+      lib,
+      files(lib + '_stub.cpp'),
+      include_directories : inc_include,
+      install : false,
+    )
+  endforeach
 
   dep_android = declare_dependency(
-    link_with : _libmesa_android_stub,
+    link_with : stub_libs,
   )
 endif

src/android_stub/meson.build

@@ -0,0 +1,20 @@
+#include <cutils/properties.h>
+#include <sync/sync.h>
+#include <hardware/hardware.h>
+#include <android/log.h>
+#include <backtrace/Backtrace.h>
+
+extern "C" {
+
+/* timeout in msecs */
+int sync_wait(int fd, int timeout)
+{
+   return 0;
+}
+
+int sync_merge(const char *name, int fd, int fd2)
+{
+   return 0;
+}
+
+}