[U-Boot] [PATCH] Handle environment variables like commands

[Stefano Babic]

The command interpreter checks always if an environment variable
for that name exists and in this case the content of the variable
is executed. It becomes possible to redefine all U-Boot commands.
A new "builtin" command is added to be able to run builtin U-boot commands
even if they are redefined.
For this reason, builtin is a reserved word an no environment
variable can be set with this name.

Signed-off-by : Stefano Babic <sbabic at denx.de>
---
 common/cmd_nvedit.c |    8 ++++++++
 common/hush.c       |    9 ++++++++-
 common/main.c       |   37 +++++++++++++++++++++++++++++++++++++
 tools/env/fw_env.c  |    8 ++++++++
 4 files changed, 61 insertions(+), 1 deletions(-)

diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
index 637d6c9..c6e4ec7 100644
--- a/common/cmd_nvedit.c
+++ b/common/cmd_nvedit.c
@@ -161,6 +161,14 @@ int _do_setenv (int flag, int argc, char *argv[])
 	}
 
 	/*
+	 * Check for reserved words
+	 */
+	if (strcmp(name, "builtin") == 0) {
+		printf ("## Error: builtin is a reserved word. You cannot set a variable with this name\n");
+		return 1;
+	}
+
+	/*
 	 * search if variable with this name already exists
 	 */
 	oldval = -1;
diff --git a/common/hush.c b/common/hush.c
index 093c428..bd7b223 100644
--- a/common/hush.c
+++ b/common/hush.c
@@ -1677,9 +1677,16 @@ static int run_pipe_real(struct pipe *pi)
 					child->argv[i]);
 				return -1;
 			}
-			/* Look up command in command table */
 
+			/* Check if exists a variable with that name, builtin is forbidden */
+			if ((strcmp (child->argv[i], "builtin") != 0) && (p = getenv (child->argv[i])) != NULL )  {
+				int rcode;
+				rcode = (parse_string_outer(p,
+			                    FLAG_PARSE_SEMICOLON | FLAG_EXIT_FROM_LOOP) != 0);
+				return rcode;
+			}
 
+			/* Look up command in command table */
 			if ((cmdtp = find_cmd(child->argv[i])) == NULL) {
 				printf ("Unknown command '%s' - try 'help'\n", child->argv[i]);
 				return -1;	/* give up after bad command */
diff --git a/common/main.c b/common/main.c
index c06ea07..d2be2ac 100644
--- a/common/main.c
+++ b/common/main.c
@@ -1289,6 +1289,7 @@ int run_command (const char *cmd, int flag)
 	int argc, inquotes;
 	int repeatable = 1;
 	int rc = 0;
+	char *runenv;
 
 #ifdef DEBUG_PARSER
 	printf ("[RUN_COMMAND] cmd[%p]=\"", cmd);
@@ -1357,6 +1358,13 @@ int run_command (const char *cmd, int flag)
 			continue;
 		}
 
+		if ((strcmp (argv[0], "builtin") != 0) && ((runenv = getenv (argv[0])) != NULL ))  {
+			if (run_command(runenv,flag) == -1) {
+				rc = -1;
+			}
+			continue;
+		}
+
 		/* Look up command in command table */
 		if ((cmdtp = find_cmd(argv[0])) == NULL) {
 			printf ("Unknown command '%s' - try 'help'\n", argv[0]);
@@ -1433,3 +1441,32 @@ int do_run (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
 	return 0;
 }
 #endif
+
+int do_builtin (cmd_tbl_t * cmdtp, int flag, int argc, char *argv[])
+{
+	int i;
+
+	if (argc < 2) {
+		printf ("Usage:\n%s\n", cmdtp->usage);
+		return 1;
+	}
+
+	/* Look up command in command table */
+	if ((cmdtp = find_cmd(argv[1])) == NULL) {
+		printf ("Unknown builtin command '%s' - try 'help'\n", argv[1]);
+		return 1;
+	}
+
+	/* Remove builtin from arg list */
+	argc--;
+
+	/* OK - call function to do the command */
+	if ((cmdtp->cmd) (cmdtp, flag, argc, &argv[1]) != 0) {
+		return 1;
+	}
+}
+
+U_BOOT_CMD(
+	builtin,	CFG_MAXARGS,	1,	do_builtin,
+	"builtin     - run builtin commands\n",
+);
diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 6e9c34f..cc31b79 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -353,6 +353,14 @@ int fw_setenv (int argc, char *argv[])
 	name = argv[1];
 
 	/*
+	 * Check for reserved words
+	 */
+	if (strcmp(name, "builtin") == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	/*
 	 * search if variable with this name already exists
 	 */
 	for (nxt = env = environment.data; *env; env = nxt + 1) {
-- 
1.5.4.3