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Commit 049cdefe authored by Jan Beulich's avatar Jan Beulich Committed by Linus Torvalds
Browse files

[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: default avatarJan Beulich <jbeulich@novell.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent c47a3167

arch/x86_64/kernel/traps.c

+4 −4
Original line number Original line Diff line number Diff line
@@ -321,13 +321,13 @@ void handle_BUG(struct pt_regs *regs) 
	if (__copy_from_user(&f, (struct bug_frame *) regs->rip, 

	if (__copy_from_user(&f, (struct bug_frame *) regs->rip, 

			     sizeof(struct bug_frame)))

			     sizeof(struct bug_frame)))

		return; 

		return; 

	if ((unsigned long)f.filename < __PAGE_OFFSET || 

	if (f.filename >= 0 ||

	    f.ud2[0] != 0x0f || f.ud2[1] != 0x0b) 

	    f.ud2[0] != 0x0f || f.ud2[1] != 0x0b) 

		return;

		return;

	if (__get_user(tmp, f.filename))

	if (__get_user(tmp, (char *)(long)f.filename))

		f.filename = "unmapped filename"; 

		f.filename = (int)(long)"unmapped filename";

	printk("----------- [cut here ] --------- [please bite here ] ---------\n");

	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

#ifdef CONFIG_BUG

include/asm-x86_64/bug.h

+4 −6
Original line number Original line Diff line number Diff line
@@ -9,10 +9,8 @@ 
 */

 */

struct bug_frame {

struct bug_frame {

	unsigned char ud2[2];

	unsigned char ud2[2];

	unsigned char mov;

	unsigned char push;

	/* should use 32bit offset instead, but the assembler doesn't 

	signed int filename;

	   like it */

	char *filename;

	unsigned char ret;

	unsigned char ret;

	unsigned short line;

	unsigned short line;

} __attribute__((packed));

} __attribute__((packed));
@@ -25,8 +23,8 @@ struct bug_frame { 
   The magic numbers generate mov $64bitimm,%eax ; ret $offset. */

   The magic numbers generate mov $64bitimm,%eax ; ret $offset. */

#define BUG() 								\

#define BUG() 								\

	asm volatile(							\

	asm volatile(							\

	"ud2 ; .byte 0xa3 ; .quad %c1 ; .byte 0xc2 ; .short %c0" :: 	\

	"ud2 ; pushq $%c1 ; ret $%c0" :: 				\

		     "i"(__LINE__), "i" (__stringify(__FILE__)))

		     "i"(__LINE__), "i" (__FILE__))

void out_of_line_bug(void);

void out_of_line_bug(void);

#else

#else

static inline void out_of_line_bug(void) { }

static inline void out_of_line_bug(void) { }