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Re: [Xen-devel] [BUG] double fault for sale ;)

Keir Fraser wrote:
> The few stack frames you looked at already look quite innocent. They
> don't take up much stack space. OTOH it is somewhat weird to be doing
> writable pagetable work that far down the stack. It'll be interesting to
> see what was going on to cause writable pagetable state to be flushed.

Looks like an endless recursion, trace (and patch) attached.

cheers,

  Gerd

-- 
Gerd Hoffmann <kraxel@xxxxxxx>
http://www.suse.de/~kraxel/julika-dora.jpeg

(XEN) Xen stack trace from esp=ffbf4f84:
(XEN)   stack overflow fixup
(XEN) Xen stack trace from esp=ffbf5000:
(XEN)  stack ffbf5030, text ff135035 <get_page_and_type+0x34/0x57>
(XEN)  stack ffbf5050, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf5080, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf50a0, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf50e0, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf5120, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 16
(XEN)  stack ffbf5130, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf51e0, text ff135035 <get_page_and_type+0x34/0x57>, frame 44
(XEN)  stack ffbf5200, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf5230, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf5250, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf5290, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf52d0, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 16
(XEN)  stack ffbf52e0, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf5390, text ff135035 <get_page_and_type+0x34/0x57>, frame 44
(XEN)  stack ffbf53b0, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf53e0, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf5400, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf5440, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf5480, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 16
(XEN)  stack ffbf5490, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf5540, text ff135035 <get_page_and_type+0x34/0x57>, frame 44
(XEN)  stack ffbf5560, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf5590, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf55b0, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf55f0, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf5630, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 16
(XEN)  stack ffbf5640, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf56f0, text ff135035 <get_page_and_type+0x34/0x57>, frame 44
(XEN)  stack ffbf5710, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf5740, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf5760, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf57a0, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf57e0, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 16
(XEN)  stack ffbf57f0, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf58a0, text ff135035 <get_page_and_type+0x34/0x57>, frame 44
(XEN)  stack ffbf58c0, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf58f0, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf5910, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf5950, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf597c, text ff137b63 <__cpus_empty+0x18/0x1a>, frame 11
(XEN)  stack ffbf5990, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 5
(XEN)  stack ffbf59a0, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf59cc, text ff1233f5 <smp_apic_timer_interrupt+0x17/0x19>, 
frame 11
(XEN)  stack ffbf5a1c, text ff183f8e <mapcache_current_vcpu+0xb/0xc5>, frame 20
(XEN)  stack ffbf5a50, text ff135035 <get_page_and_type+0x34/0x57>, frame 13
(XEN)  stack ffbf5a70, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf5aa0, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf5aac, text ff13d1e7 <ptwr_emulated_update+0x5bd/0x5d6>, frame 3
(XEN)  stack ffbf5ac0, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 5
(XEN)  stack ffbf5b00, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf5b40, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 16
(XEN)  stack ffbf5b50, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf5b70, text ff183f8e <mapcache_current_vcpu+0xb/0xc5>, frame 8
(XEN)  stack ffbf5b80, text ff183e85 <map_domain_page+0x3c5/0x3fa>, frame 4
(XEN)  stack ffbf5c00, text ff135035 <get_page_and_type+0x34/0x57>, frame 32
(XEN)  stack ffbf5c20, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf5c50, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf5c70, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf5cb0, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf5cc0, text ff135637 <get_page_from_pagenr+0x43/0x93>, frame 4
(XEN)  stack ffbf5cf0, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 12
(XEN)  stack ffbf5d00, text ff137766 <get_page_type+0x266/0x63d>, frame 4
(XEN)  stack ffbf5d10, text ff12341c <raise_softirq+0x25/0x27>, frame 4
(XEN)  stack ffbf5d20, text ff135c12 <get_page_from_l2e+0xf5/0x131>, frame 4
(XEN)  stack ffbf5d30, text ff137c01 <__next_cpu+0x26/0x48>, frame 4
(XEN)  stack ffbf5db0, text ff135035 <get_page_and_type+0x34/0x57>, frame 32
(XEN)  stack ffbf5dd0, text ff135a93 <get_page_from_l1e+0x17c/0x206>, frame 8
(XEN)  stack ffbf5e00, text ff183b28 <map_domain_page+0x68/0x3fa>, frame 12
(XEN)  stack ffbf5e20, text ff13c80e <revalidate_l1+0xb2/0x17f>, frame 8
(XEN)  stack ffbf5e60, text ff13cb13 <ptwr_flush+0x238/0x34f>, frame 16
(XEN)  stack ffbf5e70, text ff138731 <set_foreigndom+0x13/0x228>, frame 4
(XEN)  stack ffbf5e8c, text ff184169 <unmap_domain_page+0x107/0x33c>, frame 7
(XEN)  stack ffbf5ea0, text ff13d89f <cleanup_writable_pagetable+0x64/0x86>, 
frame 5
(XEN)  stack ffbf5eb0, text ff1389df <do_mmuext_op+0x99/0xa2f>, frame 4
(XEN)  stack ffbf5ecc, text ff13d5e6 <ptwr_do_page_fault+0x37b/0x483>, frame 7
(XEN)  stack ffbf5f3c, text ff144dba <fixup_page_fault+0x39e/0x3ec>, frame 28
(XEN)  stack ffbf5f6c, text ff144fe1 <do_page_fault+0x9f/0x334>, frame 12
(XEN)  stack ffbf5f80, text ff11c5f5 <do_softirq+0xa1/0xb8>, frame 5
(XEN)  stack ffbf5f90, text ff1847df <hypercall+0x8f/0xaf>, frame 4

diff -r 14717dedba02 xen/arch/x86/x86_32/traps.c
--- a/xen/arch/x86/x86_32/traps.c       Sun May 21 19:15:58 2006
+++ b/xen/arch/x86/x86_32/traps.c       Tue May 30 15:59:30 2006
@@ -173,6 +173,51 @@
            tss->esi, tss->edi, tss->ebp, tss->esp);
     printk("ds: %04x   es: %04x   fs: %04x   gs: %04x   ss: %04x\n",
            tss->ds, tss->es, tss->fs, tss->gs, tss->ss);
+
+    {
+#define stack_words_per_line  8
+
+       unsigned long *stack, addr, *lstack;
+       int words;
+
+       addr = tss->esp;
+       stack = (void*)addr;
+       printk("Xen stack trace from "__OP"sp=%p:\n  ", stack);
+
+       if ((addr & 0xfff) > 0xf00) {
+               printk("stack overflow fixup\n");
+               while ((addr & 0xfff) > 0xf00)
+                       addr += 4;
+               stack = (void*)addr;
+               printk("Xen stack trace from "__OP"sp=%p:\n  ", stack);
+       }
+
+       lstack = NULL;
+       for (;; stack++) {
+           if (((long)stack & (STACK_SIZE-BYTES_PER_LONG)) == 0)
+               break;
+           addr = *stack;
+           if (is_kernel_text(addr)) {
+               printk("\n stack %p, text %p <", stack, _p(addr));
+               print_symbol("%s",addr);
+               printk(">");
+               if (lstack)
+                       printk(", frame %d", stack - lstack);
+               lstack = stack;
+               printk("\n");
+               words = 0;
+           } else {
+               if (stack_words_per_line == words) {
+                   printk("\n");
+                   words = 0;
+               }
+               printk(" %p", _p(addr));
+               words++;
+           }
+       }
+       printk("\n");
+    }
+
     printk("************************************\n");
     printk("CPU%d DOUBLE FAULT -- system shutdown\n", cpu);
     printk("System needs manual reset.\n");

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