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@suse.de>
Link: http://lkml.kernel.org/r/1368093749-31296-1-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c198b7e13e7bba5be02fdd04db10681bdda97337..b6a770132b67315cc7d07b3da152f2027447e2d6 100644 (file)
--- 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 22224b3b43bb4587562ea1dd1374a1f8f9e571bb..5b87d52eed0b4339262f3510ce5cf1bf46992482 100644 (file)
--- 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 7bd3bd31010623367c540755d1dcf3ba0186bdf9..4ce822ed58f5f528059012c956d5b855d6cd5c6c 100644 (file)
--- 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.c b/arch/x86/kernel/doublefault.c
new file mode 100644 (file)
index 0000000..5d3fe8d
--- /dev/null
+++ b/arch/x86/kernel/doublefault.c
@@ -0,0 +1,84 @@
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/init_task.h>
+#include <linux/fs.h>
+
+#include <asm/uaccess.h>
+#include <asm/pgtable.h>
+#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)
+
+#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)
+
+static void doublefault_fn(void)
+{
+       struct desc_ptr gdt_desc = {0, 0};
+       unsigned long gdt, tss;
+
+       native_store_gdt(&gdt_desc);
+       gdt = gdt_desc.address;
+
+       printk(KERN_EMERG "PANIC: double fault, gdt at %08lx [%d bytes]\n", gdt, gdt_desc.size);
+
+       if (ptr_ok(gdt)) {
+               gdt += GDT_ENTRY_TSS << 3;
+               tss = get_desc_base((struct desc_struct *)gdt);
+               printk(KERN_EMERG "double fault, tss at %08lx\n", tss);
+
+               if (ptr_ok(tss)) {
+                       struct x86_hw_tss *t = (struct x86_hw_tss *)tss;
+
+                       printk(KERN_EMERG "eip = %08lx, esp = %08lx\n",
+                              t->ip, t->sp);
+
+                       printk(KERN_EMERG "eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n",
+                               t->ax, t->bx, t->cx, t->dx);
+                       printk(KERN_EMERG "esi = %08lx, edi = %08lx\n",
+                               t->si, t->di);
+               }
+       }
+
+       for (;;)
+               cpu_relax();
+}
+
+struct tss_struct doublefault_tss __cacheline_aligned = {
+       .x86_tss = {
+               .sp0            = STACK_START,
+               .ss0            = __KERNEL_DS,
+               .ldt            = 0,
+               .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
+
+               .ip             = (unsigned long) doublefault_fn,
+               /* 0x2 bit is always set */
+               .flags          = X86_EFLAGS_SF | 0x2,
+               .sp             = STACK_START,
+               .es             = __USER_DS,
+               .cs             = __KERNEL_CS,
+               .ss             = __KERNEL_DS,
+               .ds             = __USER_DS,
+               .fs             = __KERNEL_PERCPU,
+
+               .__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/doublefault_32.c b/arch/x86/kernel/doublefault_32.c
deleted file mode 100644 (file)
index 155a13f..0000000
--- a/arch/x86/kernel/doublefault_32.c
+++ /dev/null
@@ -1,69 +0,0 @@
-#include <linux/mm.h>
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/init_task.h>
-#include <linux/fs.h>
-
-#include <asm/uaccess.h>
-#include <asm/pgtable.h>
-#include <asm/processor.h>
-#include <asm/desc.h>
-
-#define DOUBLEFAULT_STACKSIZE (1024)
-static unsigned long doublefault_stack[DOUBLEFAULT_STACKSIZE];
-#define STACK_START (unsigned long)(doublefault_stack+DOUBLEFAULT_STACKSIZE)
-
-#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)
-
-static void doublefault_fn(void)
-{
-       struct desc_ptr gdt_desc = {0, 0};
-       unsigned long gdt, tss;
-
-       native_store_gdt(&gdt_desc);
-       gdt = gdt_desc.address;
-
-       printk(KERN_EMERG "PANIC: double fault, gdt at %08lx [%d bytes]\n", gdt, gdt_desc.size);
-
-       if (ptr_ok(gdt)) {
-               gdt += GDT_ENTRY_TSS << 3;
-               tss = get_desc_base((struct desc_struct *)gdt);
-               printk(KERN_EMERG "double fault, tss at %08lx\n", tss);
-
-               if (ptr_ok(tss)) {
-                       struct x86_hw_tss *t = (struct x86_hw_tss *)tss;
-
-                       printk(KERN_EMERG "eip = %08lx, esp = %08lx\n",
-                              t->ip, t->sp);
-
-                       printk(KERN_EMERG "eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n",
-                               t->ax, t->bx, t->cx, t->dx);
-                       printk(KERN_EMERG "esi = %08lx, edi = %08lx\n",
-                               t->si, t->di);
-               }
-       }
-
-       for (;;)
-               cpu_relax();
-}
-
-struct tss_struct doublefault_tss __cacheline_aligned = {
-       .x86_tss = {
-               .sp0            = STACK_START,
-               .ss0            = __KERNEL_DS,
-               .ldt            = 0,
-               .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
-
-               .ip             = (unsigned long) doublefault_fn,
-               /* 0x2 bit is always set */
-               .flags          = X86_EFLAGS_SF | 0x2,
-               .sp             = STACK_START,
-               .es             = __USER_DS,
-               .cs             = __KERNEL_CS,
-               .ss             = __KERNEL_DS,
-               .ds             = __USER_DS,
-               .fs             = __KERNEL_PERCPU,
-
-               .__cr3          = __pa_nodebug(swapper_pg_dir),
-       }
-};

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 772e2a846deca5a125e06a694a6dd3ae58ceb364..167d481c5fd302a43e636716a36dd7364369bc6e 100644 (file)
--- 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).