discover/grub2: Implement save_env command

[petitboot] / discover / grub2 / env.c

diff --git a/discover/grub2/env.c b/discover/grub2/env.c
index e28c9feffd4ebcdf42c46f8fdb63915e3f65e812..90e9c69667abe47db82ee324c3f52052bba99648 100644 (file)
--- a/discover/grub2/env.c
+++ b/discover/grub2/env.c
@@ -92,16 +92,169 @@ int builtin_load_env(struct grub2_script *script,
        return 0;
 }
 
        return 0;
 }
 

+static int update_env(char *buf, int buflen, const char *name,
+               const char *value)
+{
+       /* head and tail define the pointers within the existing data that we
+        * can insert our env entry, end is the last byte of valid environment
+        * data. if tail - head != entrylen, when we'll memmove to create (or
+        * remove) space */
+       int i, j, linelen, namelen, valuelen, entrylen, delta, space;
+       char *head, *tail, *end;
+       bool replace;
+
+       namelen = strlen(name);
+       valuelen = strlen(value);
+       entrylen = namelen + strlen("=") + valuelen + strlen("\n");
+
+       head = tail = end = NULL;
+       replace = false;
+
+       /* For each line (where linelen includes the trailing \n). Find
+        * head, tail and end.
+        */
+       for (i = 0; i < buflen; i += linelen) {
+               char *eol = NULL, *sep = NULL, *line = buf + i;
+
+               /* find eol and sep */
+               for (j = 0; !eol && i + j < buflen; j++) {
+                       switch (line[j]) {
+                       case '\n':
+                               eol = line + j;
+                               break;
+                       case '=':
+                               if (!sep)
+                                       sep = line + j;
+                               break;
+                       }
+               }
+
+               /* no eol, put the new value at the start of this line,
+                * no need to shift data. This will also match the
+                * padding '#' chars at the end of the entries. */
+               if (!eol) {
+                       if (!head) {
+                               head = line;
+                               tail = head + entrylen;
+                       }
+                       end = line;
+                       break;
+               }
+
+               linelen = (eol - line) + 1;
+               end = line + linelen;
+
+               /* invalid line? may as well overwrite it with valid data */
+               if (!sep && !replace) {
+                       head = line;
+                       tail = line + linelen;
+               }
+
+               /* an existing entry for this var? We set replace, as we prefer
+                * to overwrite an existing entry (the first one, in
+                * particular) rather than use an invalid line.
+                */
+               if (sep && !replace && sep - line == namelen &&
+                               !strncmp(name, line, namelen)) {
+                       head = line;
+                       tail = line + linelen;
+                       replace = true;
+               }
+       }
+
+       if (!head || !tail || !end) {
+               pb_log("grub save_env: can't parse buffer space\n");
+               return -1;
+       }
+
+       /* how much extra space do we need? */
+       delta = entrylen - (tail - head);
+       /* how much space do we have? */
+       space = (buf + buflen) - end;
+
+       /* check we have enough space. the tail > buf-end check is required
+        * for the case where there was no eol, and we set
+        * tail = head + entrylen
+        */
+       if (delta > space || tail > buf + buflen) {
+               pb_log("grub save_env: not enough buffer space\n");
+               return -1;
+       }
+
+       /* create space between head & tail */
+       if (delta) {
+               /* for positive delta, we need to reduce the copied data size */
+               int shiftlen = delta > 0 ? delta : 0;
+               memmove(tail + delta, tail, (buf + buflen) - tail - shiftlen);
+       }
+
+       /* if we've shifted data down towards head, we'll need to append
+        * padding */
+       if (delta < 0)
+               memset(buf + buflen + delta, '#', 0 - delta);
+
+       /* set the entry data */
+       memcpy(head, name, namelen);
+       memcpy(head + namelen, "=", 1);
+       memcpy(head + namelen + 1, value, valuelen);
+       memcpy(head + namelen + 1 + valuelen, "\n", 1);
+
+       return 0;
+}
+

 int builtin_save_env(struct grub2_script *script,
                void *data __attribute__((unused)),
                int argc, char *argv[]);
 
 int builtin_save_env(struct grub2_script *script,
                void *data __attribute__((unused)),
                int argc, char *argv[]);
 

-int builtin_save_env(struct grub2_script *script __attribute__((unused)),
+int builtin_save_env(struct grub2_script *script,

                void *data __attribute__((unused)),
                void *data __attribute__((unused)),

-               int argc __attribute__((unused)),
-               char *argv[] __attribute__((unused)))
+               int argc, char *argv[])

 {
 {

-       /* todo: save */
-       return 0;
+       struct discover_device *dev = script->ctx->device;
+       int i, rc, len, siglen;
+       char *buf, *envpath;
+       const char *envfile;
+
+       /* we only support local filesystems */
+       if (!dev->mounted) {
+               pb_log("save_env: can't save to a non-mounted device (%s)\n",
+                               dev->device->id);
+               return -1;
+       }
+
+       if (argc == 3 && !strcmp(argv[1], "-f"))
+               envfile = argv[2];
+       else
+               envfile = default_envfile;
+
+       envpath = talloc_asprintf(script, "%s/%s",
+                               script_env_get(script, "prefix") ? : "",
+                               envfile);
+       buf = NULL;
+
+       rc = parser_request_file(script->ctx, dev, envpath, &buf, &len);
+
+       siglen = strlen(signature);
+
+       /* we require the environment to be pre-allocated, so abort if
+        * the file isn't present and valid */
+       if (rc || len < siglen || memcmp(buf, signature, siglen))
+               goto err;
+
+       for (i = 1; i < argc; i++) {
+               const char *name, *value;
+
+               name = argv[i];
+               value = script_env_get(script, name);
+
+               update_env(buf + siglen, len - siglen, name, value);
+       }
+
+       rc = parser_replace_file(script->ctx, dev, envpath, buf, len);
+
+err:
+       talloc_free(buf);
+       talloc_free(envpath);
+       return rc;

 }
 
 }