From: Borislav Petkov Date: Thu, 9 May 2013 10:02:29 +0000 (+0200) Subject: x86: Extend #DF debugging aid to 64-bit X-Git-Tag: firefly_0821_release~176^2~5449^2~4 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4d067d8e056d76a3327f0517c7722db55e7888fc;p=firefly-linux-kernel-4.4.55.git 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 --- 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.c b/arch/x86/kernel/doublefault.c new file mode 100644 index 000000000000..5d3fe8d36e4a --- /dev/null +++ b/arch/x86/kernel/doublefault.c @@ -0,0 +1,84 @@ +#include +#include +#include +#include +#include + +#include +#include +#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) + +#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 index 155a13f33ed8..000000000000 --- a/arch/x86/kernel/doublefault_32.c +++ /dev/null @@ -1,69 +0,0 @@ -#include -#include -#include -#include -#include - -#include -#include -#include -#include - -#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 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).