[PATCH] env: Add option to only ever append environment

[Marek Vasut]

Add configuration option which prevents the environment hash table to be
ever cleared and reloaded with different content. This is useful in case
the first environment loaded into the hash table contains e.g. sensitive
content which must not be dropped or reloaded.

Signed-off-by: Marek Vasut <marex at denx.de>
---
 env/Kconfig     | 9 +++++++++
 env/env.c       | 2 ++
 lib/hashtable.c | 4 ++++
 3 files changed, 15 insertions(+)

diff --git a/env/Kconfig b/env/Kconfig
index ca7fef682b..8166e5df91 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -604,6 +604,15 @@ config DELAY_ENVIRONMENT
 	  later by U-Boot code. With CONFIG_OF_CONTROL this is instead
 	  controlled by the value of /config/load-environment.
 
+config ENV_APPEND
+	bool "Always append the environment with new data"
+	default n
+	help
+	  If defined, the environment hash table is only ever appended with new
+	  data, but the existing hash table can never be dropped and reloaded
+	  with newly imported data. This may be used in combination with static
+	  flags to e.g. to protect variables which must not be modified.
+
 config ENV_ACCESS_IGNORE_FORCE
 	bool "Block forced environment operations"
 	default n
diff --git a/env/env.c b/env/env.c
index 024d36fdbe..967a9d36d7 100644
--- a/env/env.c
+++ b/env/env.c
@@ -204,7 +204,9 @@ int env_load(void)
 		ret = drv->load();
 		if (!ret) {
 			printf("OK\n");
+#if !CONFIG_IS_ENABLED(ENV_APPEND)
 			return 0;
+#endif
 		} else if (ret == -ENOMSG) {
 			/* Handle "bad CRC" case */
 			if (best_prio == -1)
diff --git a/lib/hashtable.c b/lib/hashtable.c
index b96dbe19be..c2bf75fb76 100644
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -822,6 +822,10 @@ int himport_r(struct hsearch_data *htab,
 	if (nvars)
 		memcpy(localvars, vars, sizeof(vars[0]) * nvars);
 
+#if CONFIG_IS_ENABLED(ENV_APPEND)
+	flag |= H_NOCLEAR;
+#endif
+
 	if ((flag & H_NOCLEAR) == 0 && !nvars) {
 		/* Destroy old hash table if one exists */
 		debug("Destroy Hash Table: %p table = %p\n", htab,
-- 
2.25.1