Simplify kallsyms_lookup()

Several kallsyms_lookup() pass dummy arguments but only need, say, module's
name.  Make kallsyms_lookup() accept NULLs where possible.

Also, makes picture clearer about what interfaces are needed for all symbol
resolving business.

Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kallsyms.c

@@ -214,8 +214,10 @@ static unsigned long get_symbol_pos(unsigned long addr,
 			symbol_end = (unsigned long)_etext;
 	}
 
-	*symbolsize = symbol_end - symbol_start;
-	*offset = addr - symbol_start;
+	if (symbolsize)
+		*symbolsize = symbol_end - symbol_start;
+	if (offset)
+		*offset = addr - symbol_start;
 
 	return low;
 }

kernel/kprobes.c

@@ -868,13 +868,13 @@ static int __kprobes show_kprobe_addr(struct seq_file *pi, void *v)
 	struct kprobe *p, *kp;
 	const char *sym = NULL;
 	unsigned int i = *(loff_t *) v;
-	unsigned long size, offset = 0;
+	unsigned long offset = 0;
 	char *modname, namebuf[128];
 
 	head = &kprobe_table[i];
 	preempt_disable();
 	hlist_for_each_entry_rcu(p, node, head, hlist) {
-		sym = kallsyms_lookup((unsigned long)p->addr, &size,
+		sym = kallsyms_lookup((unsigned long)p->addr, NULL,
 					&offset, &modname, namebuf);
 		if (p->pre_handler == aggr_pre_handler) {
 			list_for_each_entry_rcu(kp, &p->list, list)

kernel/lockdep.c

@@ -340,10 +340,7 @@ static const char *usage_str[] =
 
 const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
 {
-	unsigned long offs, size;
-	char *modname;
-
-	return kallsyms_lookup((unsigned long)key, &size, &offs, &modname, str);
+	return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
 }
 
 void

kernel/module.c

@@ -2098,8 +2098,10 @@ static const char *get_ksymbol(struct module *mod,
 	if (!best)
 		return NULL;
 
-	*size = nextval - mod->symtab[best].st_value;
-	*offset = addr - mod->symtab[best].st_value;
+	if (size)
+		*size = nextval - mod->symtab[best].st_value;
+	if (offset)
+		*offset = addr - mod->symtab[best].st_value;
 	return mod->strtab + mod->symtab[best].st_name;
 }
 

kernel/time/timer_list.c

@@ -40,11 +40,9 @@ static void print_name_offset(struct seq_file *m, void *sym)
 {
 	unsigned long addr = (unsigned long)sym;
 	char namebuf[KSYM_NAME_LEN+1];
-	unsigned long size, offset;
 	const char *sym_name;
-	char *modname;
 
-	sym_name = kallsyms_lookup(addr, &size, &offset, &modname, namebuf);
+	sym_name = kallsyms_lookup(addr, NULL, NULL, NULL, namebuf);
 	if (sym_name)
 		SEQ_printf(m, "%s", sym_name);
 	else

kernel/time/timer_stats.c

@@ -258,11 +258,9 @@ void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
 static void print_name_offset(struct seq_file *m, unsigned long addr)
 {
 	char namebuf[KSYM_NAME_LEN+1];
-	unsigned long size, offset;
 	const char *sym_name;
-	char *modname;
 
-	sym_name = kallsyms_lookup(addr, &size, &offset, &modname, namebuf);
+	sym_name = kallsyms_lookup(addr, NULL, NULL, NULL, namebuf);
 	if (sym_name)
 		seq_printf(m, "%s", sym_name);
 	else