kdb: Refactor env variables get/set code

Add two new kdb environment access methods as kdb_setenv() and
kdb_printenv() in order to abstract out environment access code
from kdb command functions.

Also, replace (char *)0 with NULL as an initializer for environment
variables array.
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/1612771342-16883-1-git-send-email-sumit.garg@linaro.org
[daniel.thompson@linaro.org: Replaced (char *)0/NULL initializers with
an array size]
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

kernel/debug/kdb/kdb_main.c

@@ -140,42 +140,18 @@ static const int __nkdb_err = ARRAY_SIZE(kdbmsgs);
  * KDB_ENVBUFSIZE if required).
  */
 
-static char *__env[] = {
+static char *__env[31] = {
 #if defined(CONFIG_SMP)
- "PROMPT=[%d]kdb> ",
+	"PROMPT=[%d]kdb> ",
 #else
- "PROMPT=kdb> ",
+	"PROMPT=kdb> ",
 #endif
- "MOREPROMPT=more> ",
- "RADIX=16",
- "MDCOUNT=8",			/* lines of md output */
- KDB_PLATFORM_ENV,
- "DTABCOUNT=30",
- "NOSECT=1",
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
- (char *)0,
+	"MOREPROMPT=more> ",
+	"RADIX=16",
+	"MDCOUNT=8",		/* lines of md output */
+	KDB_PLATFORM_ENV,
+	"DTABCOUNT=30",
+	"NOSECT=1",
 };
 
 static const int __nenv = ARRAY_SIZE(__env);
@@ -317,6 +293,63 @@ int kdbgetintenv(const char *match, int *value)
 	return diag;
 }
 
+/*
+ * kdb_setenv() - Alter an existing environment variable or create a new one.
+ * @var: Name of the variable
+ * @val: Value of the variable
+ *
+ * Return: Zero on success, a kdb diagnostic on failure.
+ */
+static int kdb_setenv(const char *var, const char *val)
+{
+	int i;
+	char *ep;
+	size_t varlen, vallen;
+
+	varlen = strlen(var);
+	vallen = strlen(val);
+	ep = kdballocenv(varlen + vallen + 2);
+	if (ep == (char *)0)
+		return KDB_ENVBUFFULL;
+
+	sprintf(ep, "%s=%s", var, val);
+
+	for (i = 0; i < __nenv; i++) {
+		if (__env[i]
+		 && ((strncmp(__env[i], var, varlen) == 0)
+		   && ((__env[i][varlen] == '\0')
+		    || (__env[i][varlen] == '=')))) {
+			__env[i] = ep;
+			return 0;
+		}
+	}
+
+	/*
+	 * Wasn't existing variable.  Fit into slot.
+	 */
+	for (i = 0; i < __nenv-1; i++) {
+		if (__env[i] == (char *)0) {
+			__env[i] = ep;
+			return 0;
+		}
+	}
+
+	return KDB_ENVFULL;
+}
+
+/*
+ * kdb_printenv() - Display the current environment variables.
+ */
+static void kdb_printenv(void)
+{
+	int i;
+
+	for (i = 0; i < __nenv; i++) {
+		if (__env[i])
+			kdb_printf("%s\n", __env[i]);
+	}
+}
+
 /*
  * kdbgetularg - This function will convert a numeric string into an
  *	unsigned long value.
@@ -374,10 +407,6 @@ int kdbgetu64arg(const char *arg, u64 *value)
  */
 int kdb_set(int argc, const char **argv)
 {
-	int i;
-	char *ep;
-	size_t varlen, vallen;
-
 	/*
 	 * we can be invoked two ways:
 	 *   set var=value    argv[1]="var", argv[2]="value"
@@ -422,37 +451,7 @@ int kdb_set(int argc, const char **argv)
 	 * Tokenizer squashed the '=' sign.  argv[1] is variable
 	 * name, argv[2] = value.
 	 */
-	varlen = strlen(argv[1]);
-	vallen = strlen(argv[2]);
-	ep = kdballocenv(varlen + vallen + 2);
-	if (ep == (char *)0)
-		return KDB_ENVBUFFULL;
-
-	sprintf(ep, "%s=%s", argv[1], argv[2]);
-
-	ep[varlen+vallen+1] = '\0';
-
-	for (i = 0; i < __nenv; i++) {
-		if (__env[i]
-		 && ((strncmp(__env[i], argv[1], varlen) == 0)
-		   && ((__env[i][varlen] == '\0')
-		    || (__env[i][varlen] == '=')))) {
-			__env[i] = ep;
-			return 0;
-		}
-	}
-
-	/*
-	 * Wasn't existing variable.  Fit into slot.
-	 */
-	for (i = 0; i < __nenv-1; i++) {
-		if (__env[i] == (char *)0) {
-			__env[i] = ep;
-			return 0;
-		}
-	}
-
-	return KDB_ENVFULL;
+	return kdb_setenv(argv[1], argv[2]);
 }
 
 static int kdb_check_regs(void)
@@ -2055,12 +2054,7 @@ static int kdb_lsmod(int argc, const char **argv)
 
 static int kdb_env(int argc, const char **argv)
 {
-	int i;
-
-	for (i = 0; i < __nenv; i++) {
-		if (__env[i])
-			kdb_printf("%s\n", __env[i]);
-	}
+	kdb_printenv();
 
 	if (KDB_DEBUG(MASK))
 		kdb_printf("KDBDEBUG=0x%x\n",