Create arch specific cache dirs during zygote startup.

The runtime expects them to exist before it's launched.
The boot image / art files are created during the first
zygote launch.

(cherry picked from commit da738713e4e2120a324e8ab6fd11aa0e54a3c66e)

Change-Id: I7472aa25c16a1cf95791af2bdf80ed0d73123872

cmds/app_process/app_main.cpp

@@ -15,6 +15,7 @@
 #include <cutils/properties.h>
 #include <cutils/trace.h>
 #include <android_runtime/AndroidRuntime.h>
+#include <private/android_filesystem_config.h>  // for AID_SYSTEM
 
 #include <stdlib.h>
 #include <stdio.h>
@@ -137,6 +138,44 @@ static size_t computeArgBlockSize(int argc, char* const argv[]) {
     return (end - start);
 }
 
+static void maybeCreateDalvikCache() {
+#if defined(__aarch64__)
+    static const char kInstructionSet[] = "arm64";
+#elif defined(__x86_64__)
+    static const char kInstructionSet[] = "x86_64";
+#elif defined(__arm__)
+    static const char kInstructionSet[] = "arm";
+#elif defined(__x86__)
+    static const char kInstructionSet[] = "x86";
+#elif defined (__mips__)
+    static const char kInstructionSet[] = "mips";
+#else
+#error "Unknown instruction set"
+#endif
+    const char* androidRoot = getenv("ANDROID_DATA");
+    LOG_ALWAYS_FATAL_IF(androidRoot == NULL, "ANDROID_DATA environment variable unset");
+
+    char dalvikCacheDir[PATH_MAX];
+    const int numChars = snprintf(dalvikCacheDir, PATH_MAX,
+            "%s/dalvik-cache/%s", androidRoot, kInstructionSet);
+    LOG_ALWAYS_FATAL_IF((numChars >= PATH_MAX || numChars < 0),
+            "Error constructing dalvik cache : %s", strerror(errno));
+
+    int result = mkdir(dalvikCacheDir, 0771);
+    LOG_ALWAYS_FATAL_IF((result < 0 && errno != EEXIST),
+            "Error creating cache dir %s : %s", dalvikCacheDir, strerror(errno));
+
+    // We always perform these steps because the directory might
+    // already exist, with wider permissions and a different owner
+    // than we'd like.
+    result = chown(dalvikCacheDir, AID_SYSTEM, AID_SYSTEM);
+    LOG_ALWAYS_FATAL_IF((result < 0), "Error changing dalvik-cache ownership : %s", strerror(errno));
+
+    result = chmod(dalvikCacheDir, 0771);
+    LOG_ALWAYS_FATAL_IF((result < 0),
+            "Error changing dalvik-cache permissions : %s", strerror(errno));
+}
+
 #if defined(__LP64__)
 static const char ABI_LIST_PROPERTY[] = "ro.product.cpu.abilist64";
 static const char ZYGOTE_NICE_NAME[] = "zygote64";
@@ -223,6 +262,9 @@ int main(int argc, char* const argv[])
         args.add(application ? String8("application") : String8("tool"));
         runtime.setClassNameAndArgs(className, argc - i, argv + i);
     } else {
+        // We're in zygote mode.
+        maybeCreateDalvikCache();
+
         if (startSystemServer) {
             args.add(String8("start-system-server"));
         }