linux-kernel - [tip:x86/cpu] x86: Extend #DF debugging aid to 64-bit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <tip-4d067d8e056d76a3327f0517c7722db55e7888fc@git.kernel.org>
Date:	Mon, 13 May 2013 16:01:37 -0700
From:	tip-bot for Borislav Petkov <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	tglx@...utronix.de, hpa@...ux.intel.com, bp@...e.de
Subject: [tip:x86/cpu] x86: Extend #DF debugging aid to 64-bit

Commit-ID:  4d067d8e056d76a3327f0517c7722db55e7888fc
Gitweb:     http://git.kernel.org/tip/4d067d8e056d76a3327f0517c7722db55e7888fc
Author:     Borislav Petkov <bp@...e.de>
AuthorDate: Thu, 9 May 2013 12:02:29 +0200
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Mon, 13 May 2013 13:42:44 -0700

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 <bp@...e.de>
Link: http://lkml.kernel.org/r/1368093749-31296-1-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
---
 arch/x86/Kconfig.debug                              |  1 -
 arch/x86/include/asm/processor.h                    |  2 +-
 arch/x86/kernel/Makefile                            |  2 +-
 arch/x86/kernel/{doublefault_32.c => doublefault.c} | 15 +++++++++++++++
 arch/x86/kernel/traps.c                             |  3 +++
 5 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c198b7e..b6a7701 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 22224b3..5b87d52 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 7bd3bd3..4ce822e 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 155a13f..5d3fe8d 100644
--- a/arch/x86/kernel/doublefault_32.c
+++ b/arch/x86/kernel/doublefault.c
@@ -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
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 772e2a8..167d481 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).
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/