Unless I'm missing something, there was previously no guarantee, when you
call get_module_symbol and subsequently dereference the pointer it
returns, that the module containing your symbol will still be present by
the time you use it.
This patch changes get_module_symbol to increment the use count of the
module when the lookup is successful, and adds the corresponding
put_module_symbol function which decrements the use count again, given the
value of the symbol.
drivers/net/8290.h wants changing to reflect this.
--- ./include/linux/module.h.smpgetsym Sun May 7 16:30:57 2000
+++ ./include/linux/module.h Sun May 7 16:32:43 2000
@@ -144,6 +144,7 @@
/* Find a symbol exported by the kernel or another module */
extern unsigned long get_module_symbol(char *, char *);
+extern void put_module_symbol(unsigned long);
extern int try_inc_mod_count(struct module *mod);
--- ./kernel/module.c.smpgetsym Sun May 7 16:30:57 2000
+++ ./kernel/module.c Sun May 7 16:37:45 2000
@@ -973,7 +973,9 @@
* Gets the address for a symbol in the given module. If modname is
* NULL, it looks for the name in any registered symbol table. If the
* modname is an empty string, it looks for the symbol in kernel exported
- * symbol tables.
+ * symbol tables. Increase the usage count of the module in which the
+ * symbol was found - it's the only way we can guarantee that it's still
+ * there by the time our caller actually uses it.
*/
unsigned long
get_module_symbol(char *modname, char *symname)
@@ -982,20 +984,48 @@
struct module_symbol *sym;
int i;
+ spin_lock(&unload_lock);
for (mp = module_list; mp; mp = mp->next) {
if (((modname == NULL) || (strcmp(mp->name, modname) == 0)) &&
- MOD_CAN_QUERY(mp) &&
+ MOD_CAN_QUERY(mp) && !(mp->flags & MOD_DELETED) &&
(mp->nsyms > 0)) {
for (i = mp->nsyms, sym = mp->syms;
i > 0; --i, ++sym) {
if (strcmp(sym->name, symname) == 0) {
+ __MOD_INC_USE_COUNT(mp);
+ spin_unlock(&unload_lock);
return sym->value;
}
}
}
}
+ spin_unlock(&unload_lock);
return 0;
+}
+
+/* Decrease the use count of the module containing a symbol with the
+ * address passed.
+ */
+void put_module_symbol(unsigned long deadsym)
+{
+ struct module *mp;
+ struct module_symbol *sym;
+ int i;
+
+ for (mp = module_list; mp; mp = mp->next) {
+ if (MOD_CAN_QUERY(mp) &&
+ (mp->nsyms > 0)) {
+ for (i = mp->nsyms, sym = mp->syms;
+ i > 0; --i, ++sym) {
+
+ if (sym->value == deadsym) {
+ __MOD_DEC_USE_COUNT(mp);
+ return;
+ }
+ }
+ }
+ }
}
/*
--- ./kernel/ksyms.c.smpgetsym Sun May 7 16:30:57 2000
+++ ./kernel/ksyms.c Sun May 7 16:31:41 2000
@@ -85,6 +85,7 @@
#ifdef CONFIG_MODULES
EXPORT_SYMBOL(get_module_symbol);
+EXPORT_SYMBOL(put_module_symbol);
EXPORT_SYMBOL(try_inc_mod_count);
#endif
EXPORT_SYMBOL(get_option);
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This archive was generated by hypermail 2b29 : Sun May 07 2000 - 21:00:21 EST