Clean up reading and writing in init.

This isn't particularly useful in and of itself, but it does introduce the
first (trivial) unit test, improves the documentation (including details
about how to debug init crashes), and made me aware of how unpleasant the
existing parser is.

I also fixed a bug in passing --- unless you thought the "peboot" and "pm"
commands were features...

Bug: 19217569
Change-Id: I6ab76129a543ce3ed3dab52ef2c638009874c3de

1 files changed, 8 insertions, 37 deletions

diff --git a/init/builtins.cpp b/init/builtins.cpp
index 9ead340..31c6a99 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -56,42 +56,15 @@ int add_environment(const char *name, const char *value);
 // System call provided by bionic but not in any header file.
 extern "C" int init_module(void *, unsigned long, const char *);
 
-static int write_file(const char *path, const char *value)
-{
-    int fd, ret, len;
-
-    fd = open(path, O_WRONLY|O_CREAT|O_NOFOLLOW|O_CLOEXEC, 0600);
-
-    if (fd < 0)
-        return -errno;
-
-    len = strlen(value);
-
-    ret = TEMP_FAILURE_RETRY(write(fd, value, len));
-
-    close(fd);
-    if (ret < 0) {
-        return -errno;
-    } else {
-        return 0;
-    }
-}
-
 static int insmod(const char *filename, char *options)
 {
-    void *module;
-    unsigned size;
-    int ret;
-
-    module = read_file(filename, &size);
-    if (!module)
+    std::string module;
+    if (!read_file(filename, &module)) {
         return -1;
+    }
 
-    ret = init_module(module, size, options);
-
-    free(module);
-
-    return ret;
+    // TODO: use finit_module for >= 3.8 kernels.
+    return init_module(&module[0], module.size(), options);
 }
 
 static int setkey(struct kbentry *kbe)
@@ -743,15 +716,13 @@ int do_write(int nargs, char **args)
 {
     const char *path = args[1];
     const char *value = args[2];
-    char prop_val[PROP_VALUE_MAX];
-    int ret;
 
-    ret = expand_props(prop_val, value, sizeof(prop_val));
-    if (ret) {
+    char expanded_value[PROP_VALUE_MAX];
+    if (expand_props(expanded_value, value, sizeof(expanded_value))) {
         ERROR("cannot expand '%s' while writing to '%s'\n", value, path);
         return -EINVAL;
     }
-    return write_file(path, prop_val);
+    return write_file(path, expanded_value);
 }
 
 int do_copy(int nargs, char **args)