From 3dab307e527f2a9bbb4f9d00240374bb93d1945f Mon Sep 17 00:00:00 2001 From: Chuck Ebbert Date: Fri, 10 Aug 2007 22:31:11 +0200 Subject: [PATCH] i386: Fix double fault handler The new percpu code has apparently broken the doublefault handler when CONFIG_DEBUG_SPINLOCK is set. Doublefault is handled by a hardware task, making the check SPIN_BUG_ON(lock->owner == current, lock, "recursion"); fault because it uses the FS register to access the percpu data for current, and that register is zero in the new TSS. (The trace I saw was on 2.6.20 where it was GS, but it looks like this will still happen with FS on 2.6.22.) Initializing FS in the doublefault_tss should fix it. AK: Also fix broken ptr_ok() and turn printks into KERN_EMERG AK: And add a PANIC prefix to make clear the system will hang AK: (e.g. x86-64 will recover) Signed-off-by: Chuck Ebbert Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/i386/kernel/doublefault.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/i386/kernel/doublefault.c b/arch/i386/kernel/doublefault.c index 265c5597efb..40978af630e 100644 --- a/arch/i386/kernel/doublefault.c +++ b/arch/i386/kernel/doublefault.c @@ -13,7 +13,7 @@ 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 + 0x1000000) +#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM) static void doublefault_fn(void) { @@ -23,23 +23,23 @@ static void doublefault_fn(void) store_gdt(&gdt_desc); gdt = gdt_desc.address; - printk("double fault, gdt at %08lx [%d bytes]\n", gdt, gdt_desc.size); + 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 = *(u16 *)(gdt+2); tss += *(u8 *)(gdt+4) << 16; tss += *(u8 *)(gdt+7) << 24; - printk("double fault, tss at %08lx\n", tss); + printk(KERN_EMERG "double fault, tss at %08lx\n", tss); if (ptr_ok(tss)) { struct i386_hw_tss *t = (struct i386_hw_tss *)tss; - printk("eip = %08lx, esp = %08lx\n", t->eip, t->esp); + printk(KERN_EMERG "eip = %08lx, esp = %08lx\n", t->eip, t->esp); - printk("eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n", + printk(KERN_EMERG "eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n", t->eax, t->ebx, t->ecx, t->edx); - printk("esi = %08lx, edi = %08lx\n", + printk(KERN_EMERG "esi = %08lx, edi = %08lx\n", t->esi, t->edi); } } @@ -63,6 +63,7 @@ struct tss_struct doublefault_tss __cacheline_aligned = { .cs = __KERNEL_CS, .ss = __KERNEL_DS, .ds = __USER_DS, + .fs = __KERNEL_PERCPU, .__cr3 = __pa(swapper_pg_dir) } -- 2.20.1