From: Vivek Goyal <vgoyal@in.ibm.com>
To: Andrew Morton <akpm@osdl.org>, lkml <linux-kernel@vger.kernel.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
fastboot <fastboot@lists.osdl.org>
Subject: [RFC/PATCH 6/17][Kdump] NMI handler segment selector, stack pointer fix
Date: Mon, 28 Mar 2005 18:56:34 +0530 [thread overview]
Message-ID: <1112016394.4001.77.camel@localhost.localdomain> (raw)
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[-- Attachment #2: x86-nmi-handler-ss-esp-fix.patch --]
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From:
Subject: No Subject
Date: Mon, 28 Mar 2005 17:35:11 +0530
Message-ID: <1112011511.4001.22.camel@localhost.localdomain>
From: "Vivek Goyal" <vgoyal@in.ibm.com>
o 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 <vgoyal@in.ibm.com>
---
linux-2.6.12-rc1-mm3-1M-root/arch/i386/kernel/crash.c | 13 +++++++++++++
1 files changed, 13 insertions(+)
diff -puN arch/i386/kernel/crash.c~x86-nmi-handler-ss-esp-fix arch/i386/kernel/crash.c
--- linux-2.6.12-rc1-mm3-1M/arch/i386/kernel/crash.c~x86-nmi-handler-ss-esp-fix 2005-03-27 18:50:50.000000000 +0530
+++ linux-2.6.12-rc1-mm3-1M-root/arch/i386/kernel/crash.c 2005-03-27 18:56:16.000000000 +0530
@@ -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);
_
reply other threads:[~2005-03-28 13:47 UTC|newest]
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