kdb: fix compile error without CONFIG_KALLSYMS

If CONFIG_KGDB_KDB is set and CONFIG_KALLSYMS is not set the kernel
will fail to build with the error:

kernel/built-in.o: In function `kallsyms_symbol_next':
kernel/debug/kdb/kdb_support.c:237: undefined reference to `kdb_walk_kallsyms'
kernel/built-in.o: In function `kallsyms_symbol_complete':
kernel/debug/kdb/kdb_support.c:193: undefined reference to `kdb_walk_kallsyms'

The kdb_walk_kallsyms needs a #ifdef proper header to match the C
implementation.  This patch also fixes the compiler warnings in
kdb_support.c when compiling without CONFIG_KALLSYMS set.  The
compiler warnings are a result of the kallsyms_lookup() macro not
initializing the two of the pass by reference variables.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Reported-by: Michal Simek <monstr@monstr.eu>

kernel/debug/kdb/kdb_private.h

@@ -255,7 +255,14 @@ extern void kdb_ps1(const struct task_struct *p);
 extern void kdb_print_nameval(const char *name, unsigned long val);
 extern void kdb_send_sig_info(struct task_struct *p, struct siginfo *info);
 extern void kdb_meminfo_proc_show(void);
+#ifdef CONFIG_KALLSYMS
 extern const char *kdb_walk_kallsyms(loff_t *pos);
+#else /* ! CONFIG_KALLSYMS */
+static inline const char *kdb_walk_kallsyms(loff_t *pos)
+{
+	return NULL;
+}
+#endif /* ! CONFIG_KALLSYMS */
 extern char *kdb_getstr(char *, size_t, char *);
 
 /* Defines for kdb_symbol_print */

kernel/debug/kdb/kdb_support.c

@@ -82,8 +82,8 @@ static char *kdb_name_table[100];	/* arbitrary size */
 int kdbnearsym(unsigned long addr, kdb_symtab_t *symtab)
 {
 	int ret = 0;
-	unsigned long symbolsize;
-	unsigned long offset;
+	unsigned long symbolsize = 0;
+	unsigned long offset = 0;
 #define knt1_size 128		/* must be >= kallsyms table size */
 	char *knt1 = NULL;