From 4d55476c3f889e0f30d88e22da4682b5f10394ff Mon Sep 17 00:00:00 2001 From: Vivek Goyal Date: Sat, 25 Jun 2005 14:58:13 -0700 Subject: [PATCH] [PATCH] kdump: NMI handler segment selector, stack pointer fix CPU does not save ss and esp on stack if execution was already in kernel mode at the time of NMI occurrence. This leads to saving of erractic values for ss and esp. This patch fixes the issue. Signed-off-by: Vivek Goyal Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/crash.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/i386/kernel/crash.c b/arch/i386/kernel/crash.c index 3645ad7..31e077b 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); -- 1.8.2.3