init: add wait_for_prop builtin command

There are many use cases from vendors to exec service in background and then
use a shell scriprt to wait for the command done.

This CL is to add a wait_for_prop command to suppor those use cases.

Bug: 34746108
Test: on marlin
Change-Id: Ia81290b0928f9d375710d2daa546714f0cd65b72

1 files changed, 24 insertions, 0 deletions

diff --git a/init/builtins.cpp b/init/builtins.cpp
index 1186e9db9..965a81fbe 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -1003,6 +1003,29 @@ static int do_wait(const std::vector<std::string>& args) {
     return -1;
 }
 
+static int do_wait_for_prop(const std::vector<std::string>& args) {
+    const char* name = args[1].c_str();
+    const char* value = args[2].c_str();
+    size_t value_len = strlen(value);
+
+    if (!is_legal_property_name(name)) {
+        LOG(ERROR) << "do_wait_for_prop(\"" << name << "\", \"" << value
+                   << "\") failed: bad name";
+        return -1;
+    }
+    if (value_len >= PROP_VALUE_MAX) {
+        LOG(ERROR) << "do_wait_for_prop(\"" << name << "\", \"" << value
+                   << "\") failed: value too long";
+        return -1;
+    }
+    if (!wait_property(name, value)) {
+        LOG(ERROR) << "do_wait_for_prop(\"" << name << "\", \"" << value
+                   << "\") failed: init already in waiting";
+        return -1;
+    }
+    return 0;
+}
+
 /*
  * Callback to make a directory from the ext4 code
  */
@@ -1074,6 +1097,7 @@ BuiltinFunctionMap::Map& BuiltinFunctionMap::map() const {
         {"verity_load_state",       {0,     0,    do_verity_load_state}},
         {"verity_update_state",     {0,     0,    do_verity_update_state}},
         {"wait",                    {1,     2,    do_wait}},
+        {"wait_for_prop",           {2,     2,    do_wait_for_prop}},
         {"write",                   {2,     2,    do_write}},
     };
     return builtin_functions;