[U-Boot] [RFC PATCH 3/7] env: Introduce "export" operation and (access flag) restriction

[Bernhard Nortmann]

This patch introduces a new "export" environment operation
(env_op_export) and the corresponding access flag
ENV_FLAGS_VARACCESS_PREVENT_EXPORT; so that env_flags_validate()
may now check requests to export specific variables.

In turn, hexport_r() makes uses of this ability to suppress the
export of variables that are flagged accordingly.

Note that env_flags_validate() and hexport_r() will respect H_FORCE
and H_PROGRAMMATIC flags, allowing to bypass the export filtering.
H_PROGRAMMATIC gets used within env_print() to make sure all
variables are listed. This is necessary because env_print() is
essentially an "export to text" operation.

Signed-off-by: Bernhard Nortmann <bernhard.nortmann at web.de>
---

 cmd/nvedit.c        | 3 ++-
 common/env_flags.c  | 8 +++++++-
 include/env_flags.h | 3 ++-
 include/search.h    | 1 +
 lib/hashtable.c     | 4 ++++
 5 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/cmd/nvedit.c b/cmd/nvedit.c
index b67563b..88dbcb9 100644
--- a/cmd/nvedit.c
+++ b/cmd/nvedit.c
@@ -101,7 +101,8 @@ static int env_print(char *name, int flag)
 	}
 
 	/* print whole list */
-	len = hexport_r(&env_htab, '\n', flag, &res, 0, 0, NULL);
+	len = hexport_r(&env_htab, '\n',
+			flag | H_PROGRAMMATIC, &res, 0, 0, NULL);
 
 	if (len > 0) {
 		puts(res);
diff --git a/common/env_flags.c b/common/env_flags.c
index 1087f4e..f39d952 100644
--- a/common/env_flags.c
+++ b/common/env_flags.c
@@ -510,7 +510,7 @@ int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
 	newval = newval ? : "";
 
 	/* validate the value to match the variable type */
-	if (op != env_op_delete) {
+	if (op != env_op_delete && op != env_op_export) {
 		enum env_flags_vartype type = (enum env_flags_vartype)
 			(ENV_FLAGS_VARTYPE_BIN_MASK & item->flags);
 
@@ -560,6 +560,12 @@ int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
 			return 1;
 		}
 		break;
+	case env_op_export:
+		if (item->flags & ENV_FLAGS_VARACCESS_PREVENT_EXPORT) {
+			printf("## Don't export \"%s\"\n", name);
+			return 1;
+		}
+		break;
 	}
 
 	return 0;
diff --git a/include/env_flags.h b/include/env_flags.h
index 0dcec06..7e2362a 100644
--- a/include/env_flags.h
+++ b/include/env_flags.h
@@ -173,6 +173,7 @@ int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
 #define ENV_FLAGS_VARACCESS_PREVENT_CREATE		0x00000010
 #define ENV_FLAGS_VARACCESS_PREVENT_OVERWR		0x00000020
 #define ENV_FLAGS_VARACCESS_PREVENT_NONDEF_OVERWR	0x00000040
-#define ENV_FLAGS_VARACCESS_BIN_MASK			0x00000078
+#define ENV_FLAGS_VARACCESS_PREVENT_EXPORT		0x00000080
+#define ENV_FLAGS_VARACCESS_BIN_MASK			0x000000F8
 
 #endif /* __ENV_FLAGS_H__ */
diff --git a/include/search.h b/include/search.h
index 343dbc3..bb95265 100644
--- a/include/search.h
+++ b/include/search.h
@@ -23,6 +23,7 @@ enum env_op {
 	env_op_create,
 	env_op_delete,
 	env_op_overwrite,
+	env_op_export,
 };
 
 /* Action which shall be performed in the call the hsearch.  */
diff --git a/lib/hashtable.c b/lib/hashtable.c
index 02b4105..708319d 100644
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -621,6 +621,10 @@ ssize_t hexport_r(struct hsearch_data *htab, const char sep, int flag,
 			if ((flag & H_HIDE_DOT) && ep->key[0] == '.')
 				continue;
 
+			if (env_flags_validate(ep, NULL, env_op_export,
+					       flag & H_FORCE) != 0)
+				continue;
+
 			list[n++] = ep;
 
 			totlen += strlen(ep->key) + 2;
-- 
2.7.3