[U-Boot] [PATCH v3 3/6] env: add check/apply logic to himport_r()

Gerlando Falauto
2012-04-02T18:26:41Z

Change hashtable so that a callback function will decide whether a
variable can be overwritten, and possibly apply the changes.

So add a new field to struct hsearch_data:

o "apply" callback function to check whether a variable can be
overwritten, and possibly immediately apply the changes;
when NULL, no check is performed.

And a new argument to himport_r():
o "do_apply": whether to call the apply callback function

NOTE: This patch does not change the current behavior.

Signed-off-by: Gerlando Falauto <gerlando.falauto@keymile.com>
---
common/cmd_nvedit.c | 3 ++-
common/env_common.c | 8 +++++---
include/environment.h | 9 +++++++++
include/search.h | 14 +++++++++++++-
lib/hashtable.c | 20 +++++++++++++++++++-
5 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
index 59668a6..fc6165f 100644
--- a/common/cmd_nvedit.c
+++ b/common/cmd_nvedit.c
@@ -201,6 +201,7 @@ static int do_env_grep(cmd_tbl_t *cmdtp, int flag,
* environment variable, then (if successful) apply the changes to internals so
* to make them effective. Code for this function was taken out of
* _do_env_set(), which now calls it instead.
+ * Also called as a callback function by himport_r().
* Returns 0 in case of success, 1 in case of failure.
* When (flag & H_FORCE) is set, do not print out any error message and force
* overwriting of write-once variables.
@@ -931,7 +932,7 @@ static int do_env_import(cmd_tbl_t *cmdtp, int flag,
}

if (himport_r(&env_htab, addr, size, sep, del ? 0 : H_NOCLEAR,
- 0, NULL) == 0) {
+ 0, NULL, 0 /* do_apply */) == 0) {
error("Environment import failed: errno = %d\n", errno);
return 1;
}
diff --git a/common/env_common.c b/common/env_common.c
index a93c062..5558c1c 100644
--- a/common/env_common.c
+++ b/common/env_common.c
@@ -122,7 +122,9 @@ const uchar default_environment[] = {
"\0"
};

-struct hsearch_data env_htab;
+struct hsearch_data env_htab = {
+ .apply = env_check_apply,
+};

static uchar __env_get_char_spec(int index)
{
@@ -183,7 +185,7 @@ void set_default_env(const char *s)

if (himport_r(&env_htab, (char *)default_environment,
sizeof(default_environment), '\0', 0,
- 0, NULL) == 0)
+ 0, NULL, 0 /* do_apply */) == 0)
error("Environment import failed: errno = %d\n", errno);

gd->flags |= GD_FLG_ENV_READY;
@@ -209,7 +211,7 @@ int env_import(const char *buf, int check)
}

if (himport_r(&env_htab, (char *)ep->data, ENV_SIZE, '\0', 0,
- 0, NULL)) {
+ 0, NULL, 0 /* do_apply */)) {
gd->flags |= GD_FLG_ENV_READY;
return 1;
}
diff --git a/include/environment.h b/include/environment.h
index 1ef44f3..236e179 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -193,6 +193,15 @@ void set_default_env(const char *s);
/* Import from binary representation into hash table */
int env_import(const char *buf, int check);

+/*
+ * Check if variable "name" can be changed from oldval to newval,
+ * and if so, apply the changes (e.g. baudrate).
+ * When (flag & H_FORCE) is set, it does not print out any error
+ * message and forces overwriting of write-once variables.
+ */
+int env_check_apply(const char *name, const char *oldval,
+ const char *newval, int flag);
+
#endif /* DO_DEPS_ONLY */

#endif /* _ENVIRONMENT_H_ */
diff --git a/include/search.h b/include/search.h
index 94d75fc..721c8ac 100644
--- a/include/search.h
+++ b/include/search.h
@@ -57,6 +57,16 @@ struct hsearch_data {
struct _ENTRY *table;
unsigned int size;
unsigned int filled;
+/*
+ * Callback function which will check whether the given change for variable
+ * "name" from "oldval" to "newval" may be applied or not, and possibly apply
+ * such change.
+ * When (flag & H_FORCE) is set, it shall not print out any error message and
+ * shall force overwriting of write-once variables.
+.* Must return 0 for approval, 1 for denial.
+ */
+ int (*apply)(const char *name, const char *oldval,
+ const char *newval, int flag);
};

/* Create a new hashing table which will at most contain NEL elements. */
@@ -97,10 +107,12 @@ extern ssize_t hexport_r(struct hsearch_data *__htab,
/*
* nvars: length of vars array
* vars: array of strings (variable names) to import (nvars == 0 means all)
+ * do_apply: whether to call callback function to check the new argument,
+ * and possibly apply changes (false means accept everything)
*/
extern int himport_r(struct hsearch_data *__htab,
const char *__env, size_t __size, const char __sep,
- int __flag, int nvars, char * const vars[]);
+ int __flag, int nvars, char * const vars[], int do_apply);

/* Flags for himport_r() */
#define H_NOCLEAR (1 << 0) /* do not clear hash table before importing */
diff --git a/lib/hashtable.c b/lib/hashtable.c
index 0610e86..6cfba56 100644
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -658,7 +658,7 @@ static int is_var_in_set(const char *name, int nvars, char * const vars[])

int himport_r(struct hsearch_data *htab,
const char *env, size_t size, const char sep, int flag,
- int nvars, char * const vars[])
+ int nvars, char * const vars[], int do_apply)
{
char *data, *sp, *dp, *name, *value;

@@ -772,6 +772,24 @@ int himport_r(struct hsearch_data *htab,
e.key = name;
e.data = value;

+ /* if there is an apply function, check what it has to say */
+ if (do_apply && htab->apply != NULL) {
+ debug("searching before calling cb function"
+ " for %s\n", name);
+ /*
+ * Search for variable in existing env, so to pass
+ * its previous value to the apply callback
+ */
+ hsearch_r(e, FIND, &rv, htab);
+ debug("previous value was %s\n", rv ? rv->data : "");
+ if (htab->apply(name, rv ? rv->data : NULL,
+ value, flag)) {
+ debug("callback function refused to set"
+ " variable %s, skipping it!\n", name);
+ continue;
+ }
+ }
+
hsearch_r(e, ENTER, &rv, htab);
if (rv == NULL) {
printf("himport_r: can't insert \"%s=%s\" into hash table\n",
--
1.7.1