debug: add notifier chain debugging, v2

- unbreak ia64 (and powerpc) where function pointers dont point at code but at data (reported by Tony Luck) [ [email protected]: various cleanups ] Signed-off-by: Arjan van de Ven <[email protected]> Signed-off-by: Ingo Molnar <[email protected]>
torvalds · Sep 10, 2008 · ab7476c · ab7476c
1 parent fb822db
commit ab7476c
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Showing 4 changed files with 21 additions and 10 deletions.
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
@@ -187,6 +187,9 @@ extern unsigned long long memparse(char *ptr, char **retptr);
 extern int core_kernel_text(unsigned long addr);
 extern int __kernel_text_address(unsigned long addr);
 extern int kernel_text_address(unsigned long addr);
+extern int func_ptr_is_kernel_text(void *ptr);
+extern void *dereference_function_descriptor(void *ptr);
+
 struct pid;
 extern struct pid *session_of_pgrp(struct pid *pgrp);
 

diff --git a/kernel/extable.c b/kernel/extable.c
@@ -66,3 +66,19 @@ int kernel_text_address(unsigned long addr)
  return 1;
  return module_text_address(addr) != NULL;
 }
+
+/*
+ * On some architectures (PPC64, IA64) function pointers
+ * are actually only tokens to some data that then holds the
+ * real function address. As a result, to find if a function
+ * pointer is part of the kernel text, we need to do some
+ * special dereferencing first.
+ */
+int func_ptr_is_kernel_text(void *ptr)
+{
+ unsigned long addr;
+ addr = (unsigned long) dereference_function_descriptor(ptr);
+ if (core_kernel_text(addr))
+ return 1;
+ return module_text_address(addr) != NULL;
+}
diff --git a/kernel/notifier.c b/kernel/notifier.c
@@ -21,10 +21,6 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list);
 static int notifier_chain_register(struct notifier_block **nl,
  struct notifier_block *n)
 {
- if (!kernel_text_address((unsigned long)n->notifier_call)) {
- WARN(1, "Invalid notifier registered!");
- return 0;
- }
  while ((*nl) != NULL) {
  if (n->priority > (*nl)->priority)
  break;
@@ -38,10 +34,6 @@ static int notifier_chain_register(struct notifier_block **nl,
 static int notifier_chain_cond_register(struct notifier_block **nl,
  struct notifier_block *n)
 {
- if (!kernel_text_address((unsigned long)n->notifier_call)) {
- WARN(1, "Invalid notifier registered!");
- return 0;
- }
  while ((*nl) != NULL) {
  if ((*nl) == n)
  return 0;
@@ -92,7 +84,7 @@ static int __kprobes notifier_call_chain(struct notifier_block **nl,
  next_nb = rcu_dereference(nb->next);
 
 #ifdef CONFIG_DEBUG_NOTIFIERS
- if (!kernel_text_address((unsigned long)nb->notifier_call)) {
+ if (unlikely(!func_ptr_is_kernel_text(nb->notifier_call))) {
  WARN(1, "Invalid notifier called!");
  nb = next_nb;
  continue;

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
@@ -513,7 +513,7 @@ static char *string(char *buf, char *end, char *s, int field_width, int precisio
  return buf;
 }
 
-static inline void *dereference_function_descriptor(void *ptr)
+void *dereference_function_descriptor(void *ptr)
 {
 #if defined(CONFIG_IA64) || defined(CONFIG_PPC64)
  void *p;