[Xen-devel] [PATCH] Avoid double faults in stacktrace

["Robert S. Phillips" <rphillips@xxxxxxxxxxxxxxx>]

This patch changes the guest_mode macro so it does not double-fault
when faced with a bogus stack pointer.

Signed-off-by: Robert S. Phillips (rphillips@xxxxxxxxxxxxxxx)

# HG changeset patch
# User rphillips@rphillips
# Node ID 4ba740e1027492b5c12daa1447b2d2c71d1cc753
# Parent  ac69f504f7c1fd7415927f2c9ca460de70f71b53

This patch changes the guest_mode macro so it does not double-fault
when faced with a bogus stack pointer.

Signed-off-by: Robert S. Phillips (rphillips@xxxxxxxxxxxxxxx)

diff -r ac69f504f7c1 -r 4ba740e10274 xen/include/asm-x86/regs.h
--- a/xen/include/asm-x86/regs.h        Tue May 16 11:50:02 2006 -0400
+++ b/xen/include/asm-x86/regs.h        Tue May 16 11:53:49 2006 -0400
@@ -35,13 +35,13 @@
 ({                                                                            \
     unsigned long diff = (char *)guest_cpu_user_regs() - (char *)(r);         \
     /* Frame pointer must point into current CPU stack. */                    \
-    ASSERT(diff < STACK_SIZE);                                                \
+    if (diff >= STACK_SIZE) printk("guestregs:%p r:%p\n", 
guest_cpu_user_regs(), r); else { \
     /* If a guest frame, it must be have guest privs (unless HVM guest).   */ \
     /* We permit CS==0 which can come from an uninitialised trap entry. */    \
     ASSERT((diff != 0) || vm86_mode(r) || ((r->cs&3) >= GUEST_KERNEL_RPL) ||  \
            (r->cs == 0) || hvm_guest(current));                              \
     /* If not a guest frame, it must be a hypervisor frame. */                \
-    ASSERT((diff == 0) || (!vm86_mode(r) && (r->cs == __HYPERVISOR_CS)));     \
+    ASSERT((diff == 0) || (!vm86_mode(r) && (r->cs == __HYPERVISOR_CS))); } \
     /* Return TRUE if it's a guest frame. */                                  \
     (diff == 0);                                                              \
 })

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