[PATCH] x86-64: reduce x86-64 bug frame by 4 bytes

As mentioned before, the size of the bug frame can be further reduced while
continuing to use instructions to encode the information.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 8 insertions, 10 deletions

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index 1dfeb07d31cc..b5e09e6b5536 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -321,13 +321,13 @@ void handle_BUG(struct pt_regs *regs)
         if (__copy_from_user(&f, (struct bug_frame *) regs->rip, 
                              sizeof(struct bug_frame)))
                 return; 
-        if ((unsigned long)f.filename < __PAGE_OFFSET || 
+        if (f.filename >= 0 ||
             f.ud2[0] != 0x0f || f.ud2[1] != 0x0b) 
                 return;
-        if (__get_user(tmp, f.filename))
-                f.filename = "unmapped filename"; 
+        if (__get_user(tmp, (char *)(long)f.filename))
+                f.filename = (int)(long)"unmapped filename";
         printk("----------- [cut here ] --------- [please bite here ] ---------\n");
-        printk(KERN_ALERT "Kernel BUG at %.50s:%d\n", f.filename, f.line);
+        printk(KERN_ALERT "Kernel BUG at %.50s:%d\n", (char *)(long)f.filename, f.line);
 } 
 
 #ifdef CONFIG_BUG
diff --git a/include/asm-x86_64/bug.h b/include/asm-x86_64/bug.h
index eed785667289..80ac1fe966ac 100644
--- a/include/asm-x86_64/bug.h
+++ b/include/asm-x86_64/bug.h
@@ -9,10 +9,8 @@
  */
 struct bug_frame {
         unsigned char ud2[2];
-        unsigned char mov;
-        /* should use 32bit offset instead, but the assembler doesn't 
-           like it */
-        char *filename;
+        unsigned char push;
+        signed int filename;
         unsigned char ret;
         unsigned short line;
 } __attribute__((packed));
@@ -25,8 +23,8 @@ struct bug_frame {
    The magic numbers generate mov $64bitimm,%eax ; ret $offset. */
 #define BUG()                                                           \
         asm volatile(                                                   \
-        "ud2 ; .byte 0xa3 ; .quad %c1 ; .byte 0xc2 ; .short %c0" ::     \
-                     "i"(__LINE__), "i" (__stringify(__FILE__)))
+        "ud2 ; pushq $%c1 ; ret $%c0" ::                                \
+                     "i"(__LINE__), "i" (__FILE__))
 void out_of_line_bug(void);
 #else
 static inline void out_of_line_bug(void) { }