From 4d067d8e056d76a3327f0517c7722db55e7888fc Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Thu, 9 May 2013 12:02:29 +0200 Subject: [PATCH] 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: Borislav Petkov Link: http://lkml.kernel.org/r/1368093749-31296-1-git-send-email-bp@alien8.de Signed-off-by: H. Peter Anvin --- arch/x86/Kconfig.debug | 1 - arch/x86/include/asm/processor.h | 2 +- arch/x86/kernel/Makefile | 2 +- .../kernel/{doublefault_32.c => doublefault.c} | 15 +++++++++++++++ arch/x86/kernel/traps.c | 3 +++ 5 files changed, 20 insertions(+), 3 deletions(-) rename arch/x86/kernel/{doublefault_32.c => doublefault.c} (84%) diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index c198b7e13e7b..b6a770132b67 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -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 diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 22224b3b43bb..5b87d52eed0b 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -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 */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 7bd3bd310106..4ce822ed58f5 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -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 diff --git a/arch/x86/kernel/doublefault_32.c b/arch/x86/kernel/doublefault.c similarity index 84% rename from arch/x86/kernel/doublefault_32.c rename to arch/x86/kernel/doublefault.c index 155a13f33ed8..5d3fe8d36e4a 100644 --- a/arch/x86/kernel/doublefault_32.c +++ b/arch/x86/kernel/doublefault.c @@ -9,6 +9,8 @@ #include #include +#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 diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 772e2a846dec..167d481c5fd3 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -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).