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>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ac22bb7..ab98cca 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -87,6 +87,10 @@ config GENERIC_IOMAP
 config GENERIC_BUG
        def_bool y
        depends on BUG
+       select GENERIC_BUG_RELATIVE_POINTERS if X86_64
+
+config GENERIC_BUG_RELATIVE_POINTERS
+       bool
 
 config GENERIC_HWEIGHT
        def_bool y

diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
index 3def206..d9cf1cd 100644 (file)
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -9,7 +9,7 @@
 #ifdef CONFIG_X86_32
 # define __BUG_C0      "2:\t.long 1b, %c0\n"
 #else
-# define __BUG_C0      "2:\t.quad 1b, %c0\n"
+# define __BUG_C0      "2:\t.long 1b - 2b, %c0 - 2b\n"
 #endif
 
 #define BUG()                                                  \

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index 12c07c1..4c794d7 100644 (file)
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -8,9 +8,17 @@
 #ifdef CONFIG_GENERIC_BUG
 #ifndef __ASSEMBLY__
 struct bug_entry {
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
        unsigned long   bug_addr;
+#else
+       signed int      bug_addr_disp;
+#endif
 #ifdef CONFIG_DEBUG_BUGVERBOSE
+#ifndef CONFIG_GENERIC_BUG_RELATIVE_POINTERS
        const char      *file;
+#else
+       signed int      file_disp;
+#endif
        unsigned short  line;
 #endif
        unsigned short  flags;

diff --git a/lib/bug.c b/lib/bug.c
index bfeafd6..300e41a 100644 (file)
--- 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;