x86: simplify stackprotector self-check
Clean up the code by removing no longer needed code;
make sure the pda is updated and kept in sync
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/asm-x86/pda.h b/include/asm-x86/pda.h
index 62b7349..a5ff5bb 100644
--- a/include/asm-x86/pda.h
+++ b/include/asm-x86/pda.h
@@ -131,4 +131,5 @@
#define PDA_STACKOFFSET (5*8)
+#define refresh_stack_canary() write_pda(stack_canary, current->stack_canary)
#endif
diff --git a/kernel/panic.c b/kernel/panic.c
index 28153ae..87445a8 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -328,37 +328,21 @@
#ifndef GCC_HAS_SP
#warning You have selected the CONFIG_CC_STACKPROTECTOR option, but the gcc used does not support this.
#endif
+
static unsigned long __stack_check_testing;
+
/*
* Self test function for the stack-protector feature.
* This test requires that the local variable absolutely has
- * a stack slot, hence the barrier()s.
+ * a stack slot.
*/
static noinline void __stack_chk_test_func(void)
{
- unsigned long foo;
- barrier();
- /*
- * we need to make sure we're not about to clobber the return address,
- * while real exploits do this, it's unhealthy on a running system.
- * Besides, if we would, the test is already failed anyway so
- * time to pull the emergency brake on it.
- */
- if ((unsigned long)__builtin_return_address(0) ==
- *(((unsigned long *)&foo)+1)) {
- printk(KERN_ERR "No -fstack-protector-stack-frame!\n");
- }
-#ifdef CONFIG_FRAME_POINTER
- /* We also don't want to clobber the frame pointer */
- if ((unsigned long)__builtin_return_address(0) ==
- *(((unsigned long *)&foo)+2)) {
- printk(KERN_ERR "No -fstack-protector-stack-frame!\n");
- }
-#endif
- if (current->stack_canary != *(((unsigned long *)&foo)+1))
- printk(KERN_ERR "No -fstack-protector canary found\n");
+ unsigned long dummy_buffer[64]; /* force gcc to use the canary */
current->stack_canary = ~current->stack_canary;
+ refresh_stack_canary();
+ dummy_buffer[3] = 1; /* fool gcc into keeping the variable */
}
static int __stack_chk_test(void)
@@ -371,6 +355,7 @@
WARN_ON(1);
};
current->stack_canary = ~current->stack_canary;
+ refresh_stack_canary();
return 0;
}
/*