1 files changed, 13 insertions, 0 deletions

diff --git a/arch/i386/kernel/crash.c b/arch/i386/kernel/crash.c
index 3645ad7ac200..31e077bb0caa 100644
--- a/arch/i386/kernel/crash.c
+++ b/arch/i386/kernel/crash.c
@@ -112,7 +112,20 @@ static atomic_t waiting_for_crash_ipi;
 
 static int crash_nmi_callback(struct pt_regs *regs, int cpu)
 {
+        struct pt_regs fixed_regs;
         local_irq_disable();
+
+        /* CPU does not save ss and esp on stack if execution is already
+         * running in kernel mode at the time of NMI occurrence. This code
+         * fixes it.
+         */
+        if (!user_mode(regs)) {
+                memcpy(&fixed_regs, regs, sizeof(*regs));
+                fixed_regs.esp = (unsigned long)&(regs->esp);
+                __asm__ __volatile__("xorl %eax, %eax;");
+                __asm__ __volatile__ ("movw %%ss, %%ax;" :"=a"(fixed_regs.xss));
+                regs = &fixed_regs;
+        }
         crash_save_this_cpu(regs, cpu);
         disable_local_APIC();
         atomic_dec(&waiting_for_crash_ipi);