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Subject[PATCH 5/5] stack overflow safe kdump (2.6.15-i386) - private nmi stack
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Date
Use a private NMI stack.

---
diff -urNp linux-2.6.15/arch/i386/kernel/irq.c
linux-2.6.15-sov/arch/i386/kernel/irq.c
--- linux-2.6.15/arch/i386/kernel/irq.c 2006-01-03 12:21:10.000000000
+0900
+++ linux-2.6.15-sov/arch/i386/kernel/irq.c 2006-01-16
22:04:07.000000000 +0900
@@ -37,11 +37,6 @@ void ack_bad_irq(unsigned int irq)
/*
* per-CPU IRQ handling contexts (thread information and stack)
*/
-union irq_ctx {
- struct thread_info tinfo;
- u32 stack[THREAD_SIZE/sizeof(u32)];
-};
-
static union irq_ctx *hardirq_ctx[NR_CPUS];
static union irq_ctx *softirq_ctx[NR_CPUS];
#endif
@@ -154,6 +149,8 @@ void irq_ctx_init(int cpu)

printk("CPU %u irqstacks, hard=%p soft=%p\n",
cpu,hardirq_ctx[cpu],softirq_ctx[cpu]);
+
+ nmi_ctx_init(cpu);
}

void irq_ctx_exit(int cpu)
diff -urNp linux-2.6.15/arch/i386/kernel/traps.c
linux-2.6.15-sov/arch/i386/kernel/traps.c
--- linux-2.6.15/arch/i386/kernel/traps.c 2006-01-16 22:00:54.000000000
+0900
+++ linux-2.6.15-sov/arch/i386/kernel/traps.c 2006-01-16
22:05:51.000000000 +0900
@@ -643,6 +643,13 @@ static int dummy_nmi_callback(struct pt_

static nmi_callback_t nmi_callback = dummy_nmi_callback;

+#ifdef CONFIG_4KSTACKS
+/*
+ * per-CPU NMI handling contexts (thread information and stack)
+ */
+static union irq_ctx *nmi_ctx[NR_CPUS];
+#endif /* CONFIG_4KSTACKS */
+
static fastcall unsigned int __do_nmi(struct pt_regs * regs, long
error_code)
{
int cpu;
@@ -657,7 +664,43 @@ static fastcall unsigned int __do_nmi(st
return 0;
}

+#ifdef CONFIG_4KSTACKS
+#define _do_nmi(regs, error_code, nmih) \
+{ \
+ union irq_ctx *curctx, *nmictx; \
+ u32 *isp; \
+ \
+ curctx = (union irq_ctx *) current_thread_info(); \
+ nmictx = nmi_ctx[safe_smp_processor_id()]; \
+ \
+ /* \
+ * This is where we switch to the NMI stack. \
+ */ \
+ if (curctx != nmictx) { \
+ int arg1, arg2, ebx; \
+ \
+ /* build the stack frame on the IRQ stack */ \
+ isp = (u32*) ((char *)nmictx + sizeof(*nmictx)); \
+ if (!virt_addr_valid(curctx)) \
+ nmictx->tinfo.task = NULL; \
+ else \
+ nmictx->tinfo.task = curctx->tinfo.task; \
+ nmictx->tinfo.previous_esp = current_stack_pointer; \
+ \
+ asm volatile ( \
+ " xchgl %%ebx,%%esp \n" \
+ " call "#nmih" \n" \
+ " movl %%ebx,%%esp \n" \
+ : "=a" (arg1), "=d" (arg2), "=b" (ebx) \
+ : "0" (regs), "1" (error_code), "2" (isp) \
+ : "memory", "cc", "ecx" \
+ ); \
+ } else \
+ nmih(regs, error_code); \
+}
+#else /* CONFIG_4KSTACKS */
#define _do_nmi(regs, error_code, nmih) nmih(regs, error_code);
+#endif /* CONFIG_4KSTACKS */

fastcall void do_nmi(struct pt_regs * regs, long error_code)
{
@@ -696,6 +739,46 @@ void set_crash_nmi_callback(nmi_callback
}
EXPORT_SYMBOL_GPL(set_crash_nmi_callback);

+#ifdef CONFIG_4KSTACKS
+
+/*
+ * These should really be __section__(".bss.page_aligned") as well, but
+ * gcc's 3.0 and earlier don't handle that correctly.
+ * NOTE: support for gcc 3.0 and earlier will eventually be dropped
+ */
+
+static char nmi_stack[NR_CPUS * THREAD_SIZE]
+ __attribute__((__aligned__(THREAD_SIZE)));
+
+/*
+ * Allocate per-cpu stacks for NMI processing
+ */
+void nmi_ctx_init(int cpu)
+{
+ union irq_ctx *irqctx;
+
+ if (nmi_ctx[cpu])
+ return;
+
+ irqctx = (union irq_ctx*) &nmi_stack[cpu*THREAD_SIZE];
+ irqctx->tinfo.task = NULL;
+ irqctx->tinfo.exec_domain = NULL;
+ irqctx->tinfo.cpu = cpu;
+ irqctx->tinfo.preempt_count = HARDIRQ_OFFSET;
+ irqctx->tinfo.addr_limit = MAKE_MM_SEG(0);
+
+ nmi_ctx[cpu] = irqctx;
+
+ printk("CPU %u nmistack=%p\n", cpu, nmi_ctx[cpu]);
+}
+
+void nmi_ctx_exit(int cpu)
+{
+ nmi_ctx[cpu] = NULL;
+}
+
+#endif /* CONFIG_4KSTACKS */
+
#ifdef CONFIG_KPROBES
fastcall void __kprobes do_int3(struct pt_regs *regs, long error_code)
{
diff -urNp linux-2.6.15/include/asm-i386/irq.h
linux-2.6.15-sov/include/asm-i386/irq.h
--- linux-2.6.15/include/asm-i386/irq.h 2006-01-03 12:21:10.000000000
+0900
+++ linux-2.6.15-sov/include/asm-i386/irq.h 2006-01-16
22:04:07.000000000 +0900
@@ -28,12 +28,21 @@ extern void release_vm86_irqs(struct tas
#endif

#ifdef CONFIG_4KSTACKS
- extern void irq_ctx_init(int cpu);
- extern void irq_ctx_exit(int cpu);
+union irq_ctx {
+ struct thread_info tinfo;
+ u32 stack[THREAD_SIZE/sizeof(u32)];
+};
+
+extern void irq_ctx_init(int cpu);
+extern void irq_ctx_exit(int cpu);
+extern void nmi_ctx_init(int cpu);
+extern void nmi_ctx_exit(int cpu);
# define __ARCH_HAS_DO_SOFTIRQ
#else
# define irq_ctx_init(cpu) do { } while (0)
# define irq_ctx_exit(cpu) do { } while (0)
+# define nmi_ctx_init(cpu) do { } while (0)
+# define nmi_ctx_exit(cpu) do { } while (0)
#endif

#ifdef CONFIG_IRQBALANCE

-
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