x86/mm: Expand the exception table logic to allow new handling options

[firefly-linux-kernel-4.4.55.git] / arch / x86 / mm / extable.c

diff --git a/arch/x86/mm/extable.c b/arch/x86/mm/extable.c
index 903ec1e9c3263f7f7ce6e1f5a59e7a32b224dc85..9dd7e4b7fcdee4a847f98937b9a287b826366a2d 100644 (file)
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -3,6 +3,9 @@
 #include <linux/sort.h>
 #include <asm/uaccess.h>
 
+typedef bool (*ex_handler_t)(const struct exception_table_entry *,
+                           struct pt_regs *, int);
+
 static inline unsigned long
 ex_insn_addr(const struct exception_table_entry *x)
 {
@@ -13,11 +16,56 @@ ex_fixup_addr(const struct exception_table_entry *x)
 {
        return (unsigned long)&x->fixup + x->fixup;
 }
+static inline ex_handler_t
+ex_fixup_handler(const struct exception_table_entry *x)
+{
+       return (ex_handler_t)((unsigned long)&x->handler + x->handler);
+}
 
-int fixup_exception(struct pt_regs *regs)
+bool ex_handler_default(const struct exception_table_entry *fixup,
+                      struct pt_regs *regs, int trapnr)
 {
-       const struct exception_table_entry *fixup;
-       unsigned long new_ip;
+       regs->ip = ex_fixup_addr(fixup);
+       return true;
+}
+EXPORT_SYMBOL(ex_handler_default);
+
+bool ex_handler_fault(const struct exception_table_entry *fixup,
+                    struct pt_regs *regs, int trapnr)
+{
+       regs->ip = ex_fixup_addr(fixup);
+       regs->ax = trapnr;
+       return true;
+}
+EXPORT_SYMBOL_GPL(ex_handler_fault);
+
+bool ex_handler_ext(const struct exception_table_entry *fixup,
+                  struct pt_regs *regs, int trapnr)
+{
+       /* Special hack for uaccess_err */
+       current_thread_info()->uaccess_err = 1;
+       regs->ip = ex_fixup_addr(fixup);
+       return true;
+}
+EXPORT_SYMBOL(ex_handler_ext);
+
+bool ex_has_fault_handler(unsigned long ip)
+{
+       const struct exception_table_entry *e;
+       ex_handler_t handler;
+
+       e = search_exception_tables(ip);
+       if (!e)
+               return false;
+       handler = ex_fixup_handler(e);
+
+       return handler == ex_handler_fault;
+}
+
+int fixup_exception(struct pt_regs *regs, int trapnr)
+{
+       const struct exception_table_entry *e;
+       ex_handler_t handler;
 
 #ifdef CONFIG_PNPBIOS
        if (unlikely(SEGMENT_IS_PNP_CODE(regs->cs))) {
@@ -33,42 +81,34 @@ int fixup_exception(struct pt_regs *regs)
        }
 #endif
 
-       fixup = search_exception_tables(regs->ip);
-       if (fixup) {
-               new_ip = ex_fixup_addr(fixup);
-
-               if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
-                       /* Special hack for uaccess_err */
-                       current_thread_info()->uaccess_err = 1;
-                       new_ip -= 0x7ffffff0;
-               }
-               regs->ip = new_ip;
-               return 1;
-       }
+       e = search_exception_tables(regs->ip);
+       if (!e)
+               return 0;
 
-       return 0;
+       handler = ex_fixup_handler(e);
+       return handler(e, regs, trapnr);
 }
 
 /* Restricted version used during very early boot */
 int __init early_fixup_exception(unsigned long *ip)
 {
-       const struct exception_table_entry *fixup;
+       const struct exception_table_entry *e;
        unsigned long new_ip;
+       ex_handler_t handler;
 
-       fixup = search_exception_tables(*ip);
-       if (fixup) {
-               new_ip = ex_fixup_addr(fixup);
+       e = search_exception_tables(*ip);
+       if (!e)
+               return 0;
 
-               if (fixup->fixup - fixup->insn >= 0x7ffffff0 - 4) {
-                       /* uaccess handling not supported during early boot */
-                       return 0;
-               }
+       new_ip  = ex_fixup_addr(e);
+       handler = ex_fixup_handler(e);
 
-               *ip = new_ip;
-               return 1;
-       }
+       /* special handling not supported during early boot */
+       if (handler != ex_handler_default)
+               return 0;
 
-       return 0;
+       *ip = new_ip;
+       return 1;
 }
 
 /*
@@ -133,6 +173,8 @@ void sort_extable(struct exception_table_entry *start,
                i += 4;
                p->fixup += i;
                i += 4;
+               p->handler += i;
+               i += 4;
        }
 
        sort(start, finish - start, sizeof(struct exception_table_entry),
@@ -145,6 +187,8 @@ void sort_extable(struct exception_table_entry *start,
                i += 4;
                p->fixup -= i;
                i += 4;
+               p->handler -= i;
+               i += 4;
        }
 }