x86: uaccess: introduce try and catch framework
Impact: introduce new uaccess exception handling framework
Introduce {get|put}_user_try and {get|put}_user_catch as new uaccess exception
handling framework.
{get|put}_user_try begins exception block and {get|put}_user_catch(err) ends
the block and gets err if an exception occured in {get|put}_user_ex() in the
block. The exception is stored thread_info->uaccess_err.
The example usage of this framework is below;
int func()
{
int err = 0;
get_user_try {
get_user_ex(...);
get_user_ex(...);
:
} get_user_catch(err);
return err;
}
Note: get_user_ex() is not clear the value when an exception occurs, it's
different from the behavior of __get_user(), but I think it doesn't matter.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 7e8db53..61b41ca 100644
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -23,6 +23,12 @@
fixup = search_exception_tables(regs->ip);
if (fixup) {
+ /* If fixup is less than 16, it means uaccess error */
+ if (fixup->fixup < 16) {
+ current_thread_info()->uaccess_err = -EFAULT;
+ regs->ip += fixup->fixup;
+ return 1;
+ }
regs->ip = fixup->fixup;
return 1;
}