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Commit c31a0bf3 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Linus Torvalds
Browse files

[PATCH] Generic BUG for x86-64 



This makes x86-64 use the generic BUG machinery.

The main advantage in using the generic BUG machinery for x86-64 is that
the inlined overhead of BUG is just the ud2a instruction; the file+line
information are no longer inlined into the instruction stream.  This
reduces cache pollution.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy@goop.org>
Cc: Andi Kleen <ak@muc.de>
Cc: Hugh Dickens <hugh@veritas.com>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 91768d6c

arch/x86_64/Kconfig

+5 −0
Original line number Diff line number Diff line
@@ -96,6 +96,11 @@ config AUDIT_ARCH 
	bool

	default y



config GENERIC_BUG

	bool

	default y

	depends on BUG



source "init/Kconfig"

arch/x86_64/kernel/module.c

+4 −1
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/string.h>

#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/bug.h>



#include <asm/system.h>

#include <asm/page.h>
@@ -173,10 +174,12 @@ int module_finalize(const Elf_Ehdr *hdr, 
					    lseg, lseg + locks->sh_size,

					    tseg, tseg + text->sh_size);

	}

	return 0;



	return module_bug_finalize(hdr, sechdrs, me);

}



void module_arch_cleanup(struct module *mod)

{

	alternatives_smp_module_del(mod);

	module_bug_cleanup(mod);

}

arch/x86_64/kernel/traps.c

+12 −24
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
#include <linux/kexec.h>

#include <linux/unwind.h>

#include <linux/uaccess.h>

#include <linux/bug.h>



#include <asm/system.h>

#include <asm/io.h>
@@ -524,29 +525,14 @@ bad: 
	printk("\n");

}	



void handle_BUG(struct pt_regs *regs)

int is_valid_bugaddr(unsigned long rip)

{

	struct bug_frame f;

	long len;

	const char *prefix = "";

	unsigned short ud2;



	if (user_mode(regs))

		return; 

	if (__copy_from_user(&f, (const void __user *) regs->rip,

			     sizeof(struct bug_frame)))

		return; 

	if (f.filename >= 0 ||

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

		return;

	len = __strnlen_user((char *)(long)f.filename, PATH_MAX) - 1;

	if (len < 0 || len >= PATH_MAX)

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

	else if (len > 50) {

		f.filename += len - 50;

		prefix = "...";

	}

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

	printk(KERN_ALERT "Kernel BUG at %s%.50s:%d\n", prefix, (char *)(long)f.filename, f.line);

	if (__copy_from_user(&ud2, (const void __user *) rip, sizeof(ud2)))

		return 0;



	return ud2 == 0x0b0f;

}



#ifdef CONFIG_BUG
@@ -627,7 +613,9 @@ void die(const char * str, struct pt_regs * regs, long err) 
{

	unsigned long flags = oops_begin();



	handle_BUG(regs);

	if (!user_mode(regs))

		report_bug(regs->rip);



	__die(str, regs, err);

	oops_end(flags);

	do_exit(SIGSEGV);

arch/x86_64/kernel/vmlinux.lds.S

+2 −0
Original line number Diff line number Diff line
@@ -51,6 +51,8 @@ SECTIONS 


  RODATA



  BUG_TABLE



  . = ALIGN(PAGE_SIZE);        /* Align data segment to page size boundary */

				/* Data */

  .data : AT(ADDR(.data) - LOAD_OFFSET) {

include/asm-x86_64/bug.h

+22 −22
Original line number Diff line number Diff line 
#ifndef __ASM_X8664_BUG_H

#define __ASM_X8664_BUG_H 1



#include <linux/stringify.h>



/*

 * Tell the user there is some problem.  The exception handler decodes 

 * this frame.

 */

struct bug_frame {

	unsigned char ud2[2];

	unsigned char push;

	signed int filename;

	unsigned char ret;

	unsigned short line;

} __attribute__((packed));



#ifdef CONFIG_BUG

#define HAVE_ARCH_BUG

/* We turn the bug frame into valid instructions to not confuse

   the disassembler. Thanks to Jan Beulich & Suresh Siddha

   for nice instruction selection.

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



#ifdef CONFIG_DEBUG_BUGVERBOSE

#define BUG()								\

	asm volatile(							\

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

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

	do {								\

		asm volatile("1:\tud2\n"				\

			     ".pushsection __bug_table,\"a\"\n"		\

			     "2:\t.quad 1b, %c0\n"			\

			     "\t.word %c1, 0\n"				\

			     "\t.org 2b+%c2\n"				\

			     ".popsection"				\

			     : : "i" (__FILE__), "i" (__LINE__),	\

			        "i" (sizeof(struct bug_entry)));	\

		for(;;) ;						\

	} while(0)

#else

#define BUG()								\

	do {								\

		asm volatile("ud2");					\

		for(;;) ;						\

	} while(0)

#endif



void out_of_line_bug(void);

#else

static inline void out_of_line_bug(void) { }