allow bug table entries to use relative pointers (and use it on x86-64)

Impact: reduce bug table size

This allows reducing the bug table size by half. Perhaps there are
other 64-bit architectures that could also make use of this.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 17 insertions, 2 deletions

diff --git a/lib/bug.c b/lib/bug.c
index bfeafd60ee9f..300e41afbf97 100644
--- a/lib/bug.c
+++ b/lib/bug.c
@@ -5,6 +5,8 @@
 
   CONFIG_BUG - emit BUG traps.  Nothing happens without this.
   CONFIG_GENERIC_BUG - enable this code.
+  CONFIG_GENERIC_BUG_RELATIVE_POINTERS - use 32-bit pointers relative to
+        the containing struct bug_entry for bug_addr and file.
   CONFIG_DEBUG_BUGVERBOSE - emit full file+line information for each BUG
 
   CONFIG_BUG and CONFIG_DEBUG_BUGVERBOSE are potentially user-settable
@@ -43,6 +45,15 @@
 
 extern const struct bug_entry __start___bug_table[], __stop___bug_table[];
 
+static inline unsigned long bug_addr(const struct bug_entry *bug)
+{
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
+        return bug->bug_addr;
+#else
+        return (unsigned long)bug + bug->bug_addr_disp;
+#endif
+}
+
 #ifdef CONFIG_MODULES
 static LIST_HEAD(module_bug_list);
 
@@ -55,7 +66,7 @@ static const struct bug_entry *module_find_bug(unsigned long bugaddr)
                 unsigned i;
 
                 for (i = 0; i < mod->num_bugs; ++i, ++bug)
-                        if (bugaddr == bug->bug_addr)
+                        if (bugaddr == bug_addr(bug))
                                 return bug;
         }
         return NULL;
@@ -108,7 +119,7 @@ const struct bug_entry *find_bug(unsigned long bugaddr)
         const struct bug_entry *bug;
 
         for (bug = __start___bug_table; bug < __stop___bug_table; ++bug)
-                if (bugaddr == bug->bug_addr)
+                if (bugaddr == bug_addr(bug))
                         return bug;
 
         return module_find_bug(bugaddr);
@@ -133,7 +144,11 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
 
         if (bug) {
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
                 file = bug->file;
+#else
+                file = (const char *)bug + bug->file_disp;
+#endif
                 line = bug->line;
 #endif
                 warning = (bug->flags & BUGFLAG_WARNING) != 0;