[PATCH] Add kallsyms_lookupname()

From: Rusty Russell <rusty@au1.ibm.com>

Attached patch adds a kallsyms_lookupname() function for lookups of a
symbol name to an address.  Debuggers such as ppc[64] xmon can use this.

It's intentionally not exported as a symbol for module use, since it
can be used to circumvent other symbol export restrictions.

include/linux/kallsyms.h

@@ -8,6 +8,9 @@
 #include <linux/config.h>
 
 #ifdef CONFIG_KALLSYMS
+/* Lookup the address for a symbol. Returns 0 if not found. */
+unsigned long kallsyms_lookup_name(const char *name);
+
 /* Lookup an address.  modname is set to NULL if it's in the kernel. */
 const char *kallsyms_lookup(unsigned long addr,
 			    unsigned long *symbolsize,
@@ -19,6 +22,11 @@ extern void __print_symbol(const char *fmt, unsigned long address);
 
 #else /* !CONFIG_KALLSYMS */
 
+static inline unsigned long kallsyms_lookup_name(const char *name)
+{
+	return 0;
+}
+
 static inline const char *kallsyms_lookup(unsigned long addr,
 					  unsigned long *symbolsize,
 					  unsigned long *offset,

include/linux/module.h

@@ -282,6 +282,10 @@ struct module *module_get_kallsym(unsigned int symnum,
 				  unsigned long *value,
 				  char *type,
 				  char namebuf[128]);
+
+/* Look for this name: can be of form module:name. */
+unsigned long module_kallsyms_lookup_name(const char *name);
+
 int is_exported(const char *name, const struct module *mod);
 
 extern void __module_put_and_exit(struct module *mod, long code)
@@ -434,6 +438,11 @@ static inline struct module *module_get_kallsym(unsigned int symnum,
 	return NULL;
 }
 
+static inline unsigned long module_kallsyms_lookup_name(const char *name)
+{
+	return 0;
+}
+
 static inline int is_exported(const char *name, const struct module *mod)
 {
 	return 0;

kernel/kallsyms.c

@@ -37,6 +37,25 @@ static inline int is_kernel_text(unsigned long addr)
 	return 0;
 }
 
+/* Lookup the address for this symbol. Returns 0 if not found. */
+unsigned long kallsyms_lookup_name(const char *name)
+{
+	char namebuf[128];
+	unsigned long i;
+	char *knames;
+
+	for (i = 0, knames = kallsyms_names; i < kallsyms_num_syms; i++) {
+		unsigned prefix = *knames++;
+
+		strlcpy(namebuf + prefix, knames, 127 - prefix);
+		if (strcmp(namebuf, name) == 0)
+			return kallsyms_addresses[i];
+
+		knames += strlen(knames) + 1;
+	}
+	return module_kallsyms_lookup_name(name);
+}
+
 /* Lookup an address.  modname is set to NULL if it's in the kernel. */
 const char *kallsyms_lookup(unsigned long addr,
 			    unsigned long *symbolsize,

kernel/module.c

@@ -1893,6 +1893,37 @@ struct module *module_get_kallsym(unsigned int symnum,
 	up(&module_mutex);
 	return NULL;
 }
+
+static unsigned long mod_find_symname(struct module *mod, const char *name)
+{
+	unsigned int i;
+
+	for (i = 0; i < mod->num_symtab; i++)
+		if (strcmp(name, mod->strtab+mod->symtab[i].st_name) == 0)
+			return mod->symtab[i].st_value;
+	return 0;
+}
+
+/* Look for this name: can be of form module:name. */
+unsigned long module_kallsyms_lookup_name(const char *name)
+{
+	struct module *mod;
+	char *colon;
+	unsigned long ret = 0;
+
+	/* Don't lock: we're in enough trouble already. */
+	if ((colon = strchr(name, ':')) != NULL) {
+		*colon = '\0';
+		if ((mod = find_module(name)) != NULL)
+			ret = mod_find_symname(mod, colon+1);
+		*colon = ':';
+	} else {
+		list_for_each_entry(mod, &modules, list)
+			if ((ret = mod_find_symname(mod, name)) != 0)
+				break;
+	}
+	return ret;
+}
 #endif /* CONFIG_KALLSYMS */
 
 /* Called by the /proc file system to return a list of modules. */