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Commit 4d067d8e authored by Borislav Petkov's avatar Borislav Petkov Committed by H. Peter Anvin
Browse files

x86: Extend #DF debugging aid to 64-bit 



It is sometimes very helpful to be able to pinpoint the location which
causes a double fault before it turns into a triple fault and the
machine reboots. We have this for 32-bit already so extend it to 64-bit.
On 64-bit we get the register snapshot at #DF time and not from the
first exception which actually causes the #DF. It should be close
enough, though.

[ hpa: and definitely better than nothing, which is what we have now. ]

Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1368093749-31296-1-git-send-email-bp@alien8.de


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent f722406f

arch/x86/Kconfig.debug

+0 −1
Original line number Diff line number Diff line
@@ -122,7 +122,6 @@ config DEBUG_NX_TEST 
config DOUBLEFAULT

	default y

	bool "Enable doublefault exception handler" if EXPERT

	depends on X86_32

	---help---

	  This option allows trapping of rare doublefault exceptions that

	  would otherwise cause a system to silently reboot. Disabling this

arch/x86/include/asm/processor.h

+1 −1
Original line number Diff line number Diff line
@@ -981,5 +981,5 @@ bool xen_set_default_idle(void); 
#endif



void stop_this_cpu(void *dummy);



void df_debug(struct pt_regs *regs, long error_code);

#endif /* _ASM_X86_PROCESSOR_H */

arch/x86/kernel/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ obj-$(CONFIG_KEXEC) += relocate_kernel_$(BITS).o crash.o 
obj-$(CONFIG_CRASH_DUMP)	+= crash_dump_$(BITS).o

obj-y				+= kprobes/

obj-$(CONFIG_MODULES)		+= module.o

obj-$(CONFIG_DOUBLEFAULT) 	+= doublefault_32.o

obj-$(CONFIG_DOUBLEFAULT)	+= doublefault.o

obj-$(CONFIG_KGDB)		+= kgdb.o

obj-$(CONFIG_VM86)		+= vm86_32.o

obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o

arch/x86/kernel/doublefault_32.c→arch/x86/kernel/doublefault.c

+15 −0
Original line number Diff line number Diff line
@@ -9,6 +9,8 @@ 
#include <asm/processor.h>

#include <asm/desc.h>



#ifdef CONFIG_X86_32



#define DOUBLEFAULT_STACKSIZE (1024)

static unsigned long doublefault_stack[DOUBLEFAULT_STACKSIZE];

#define STACK_START (unsigned long)(doublefault_stack+DOUBLEFAULT_STACKSIZE)
@@ -67,3 +69,16 @@ struct tss_struct doublefault_tss __cacheline_aligned = { 
		.__cr3		= __pa_nodebug(swapper_pg_dir),

	}

};



/* dummy for do_double_fault() call */

void df_debug(struct pt_regs *regs, long error_code) {}



#else /* !CONFIG_X86_32 */



void df_debug(struct pt_regs *regs, long error_code)

{

	pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);

	show_regs(regs);

	panic("Machine halted.");

}

#endif

arch/x86/kernel/traps.c

+3 −0
Original line number Diff line number Diff line
@@ -254,6 +254,9 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) 
	tsk->thread.error_code = error_code;

	tsk->thread.trap_nr = X86_TRAP_DF;



#ifdef CONFIG_DOUBLEFAULT

	df_debug(regs, error_code);

#endif

	/*

	 * This is always a kernel trap and never fixable (and thus must

	 * never return).