6 files changed, 75 insertions, 56 deletions

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 8e28bf2fc3ef..29c1944a98ac 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1078,6 +1078,10 @@ static __init int setup_disablecpuid(char *arg)
 }
 __setup("clearcpuid=", setup_disablecpuid);
 
+DEFINE_PER_CPU(unsigned long, kernel_stack) =
+        (unsigned long)&init_thread_union - KERNEL_STACK_OFFSET + THREAD_SIZE;
+EXPORT_PER_CPU_SYMBOL(kernel_stack);
+
 #ifdef CONFIG_X86_64
 struct desc_ptr idt_descr = { NR_VECTORS * 16 - 1, (unsigned long) idt_table };
 struct desc_ptr debug_idt_descr = { NR_VECTORS * 16 - 1,
@@ -1094,10 +1098,6 @@ DEFINE_PER_CPU(struct task_struct *, current_task) ____cacheline_aligned =
         &init_task;
 EXPORT_PER_CPU_SYMBOL(current_task);
 
-DEFINE_PER_CPU(unsigned long, kernel_stack) =
-        (unsigned long)&init_thread_union - KERNEL_STACK_OFFSET + THREAD_SIZE;
-EXPORT_PER_CPU_SYMBOL(kernel_stack);
-
 DEFINE_PER_CPU(char *, irq_stack_ptr) =
         init_per_cpu_var(irq_stack_union.irq_stack) + IRQ_STACK_SIZE - 64;
 
diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 187d6a749c19..dca820b627d6 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -16,11 +16,33 @@
 
 #include <asm/stacktrace.h>
 
+static void *is_irq_stack(void *p, void *irq)
+{
+        if (p < irq || p >= (irq + THREAD_SIZE))
+                return NULL;
+        return irq + THREAD_SIZE;
+}
+
+
+static void *is_hardirq_stack(unsigned long *stack, int cpu)
+{
+        void *irq = per_cpu(hardirq_stack, cpu);
+
+        return is_irq_stack(stack, irq);
+}
+
+static void *is_softirq_stack(unsigned long *stack, int cpu)
+{
+        void *irq = per_cpu(softirq_stack, cpu);
+
+        return is_irq_stack(stack, irq);
+}
 
 void dump_trace(struct task_struct *task, struct pt_regs *regs,
                 unsigned long *stack, unsigned long bp,
                 const struct stacktrace_ops *ops, void *data)
 {
+        const unsigned cpu = get_cpu();
         int graph = 0;
         u32 *prev_esp;
 
@@ -40,18 +62,22 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
 
         for (;;) {
                 struct thread_info *context;
+                void *end_stack;
+
+                end_stack = is_hardirq_stack(stack, cpu);
+                if (!end_stack)
+                        end_stack = is_softirq_stack(stack, cpu);
 
-                context = (struct thread_info *)
-                        ((unsigned long)stack & (~(THREAD_SIZE - 1)));
-                bp = ops->walk_stack(context, stack, bp, ops, data, NULL, &graph);
+                context = task_thread_info(task);
+                bp = ops->walk_stack(context, stack, bp, ops, data,
+                                     end_stack, &graph);
 
                 /* Stop if not on irq stack */
-                if (task_stack_page(task) == context)
+                if (!end_stack)
                         break;
 
-                /* The previous esp is just above the context */
-                prev_esp = (u32 *) ((char *)context + sizeof(struct thread_info) -
-                                    sizeof(long));
+                /* The previous esp is saved on the bottom of the stack */
+                prev_esp = (u32 *)(end_stack - THREAD_SIZE);
                 stack = (unsigned long *)*prev_esp;
                 if (!stack)
                         break;
@@ -60,6 +86,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                         break;
                 touch_nmi_watchdog();
         }
+        put_cpu();
 }
 EXPORT_SYMBOL(dump_trace);
 
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index f135cc2ff301..988dc8bcaebf 100644
--- a/arch/x86/kernel/irq_32.c
+++ b/arch/x86/kernel/irq_32.c
@@ -55,16 +55,8 @@ static inline int check_stack_overflow(void) { return 0; }
 static inline void print_stack_overflow(void) { }
 #endif
 
-/*
- * per-CPU IRQ handling contexts (thread information and stack)
- */
-union irq_ctx {
-        struct thread_info      tinfo;
-        u32                     stack[THREAD_SIZE/sizeof(u32)];
-} __attribute__((aligned(THREAD_SIZE)));
-
-static DEFINE_PER_CPU(union irq_ctx *, hardirq_ctx);
-static DEFINE_PER_CPU(union irq_ctx *, softirq_ctx);
+DEFINE_PER_CPU(struct irq_stack *, hardirq_stack);
+DEFINE_PER_CPU(struct irq_stack *, softirq_stack);
 
 static void call_on_stack(void *func, void *stack)
 {
@@ -77,14 +69,22 @@ static void call_on_stack(void *func, void *stack)
                      : "memory", "cc", "edx", "ecx", "eax");
 }
 
+/* how to get the current stack pointer from C */
+register unsigned long current_stack_pointer asm("esp") __used;
+
+static inline void *current_stack(void)
+{
+        return (void *)(current_stack_pointer & ~(THREAD_SIZE - 1));
+}
+
 static inline int
 execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
 {
-        union irq_ctx *curctx, *irqctx;
+        struct irq_stack *curstk, *irqstk;
         u32 *isp, *prev_esp, arg1, arg2;
 
-        curctx = (union irq_ctx *) current_thread_info();
-        irqctx = __this_cpu_read(hardirq_ctx);
+        curstk = (struct irq_stack *) current_stack();
+        irqstk = __this_cpu_read(hardirq_stack);
 
         /*
          * this is where we switch to the IRQ stack. However, if we are
@@ -92,15 +92,13 @@ execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
          * handler) we can't do that and just have to keep using the
          * current stack (which is the irq stack already after all)
          */
-        if (unlikely(curctx == irqctx))
+        if (unlikely(curstk == irqstk))
                 return 0;
 
-        /* build the stack frame on the IRQ stack */
-        isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
-        irqctx->tinfo.task = curctx->tinfo.task;
-        /* Save the next esp after thread_info */
-        prev_esp = (u32 *) ((char *)irqctx + sizeof(struct thread_info) -
-                            sizeof(long));
+        isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
+
+        /* Save the next esp at the bottom of the stack */
+        prev_esp = (u32 *)irqstk;
         *prev_esp = current_stack_pointer;
 
         if (unlikely(overflow))
@@ -121,49 +119,39 @@ execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
  */
 void irq_ctx_init(int cpu)
 {
-        union irq_ctx *irqctx;
+        struct irq_stack *irqstk;
 
-        if (per_cpu(hardirq_ctx, cpu))
+        if (per_cpu(hardirq_stack, cpu))
                 return;
 
-        irqctx = page_address(alloc_pages_node(cpu_to_node(cpu),
+        irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
                                                THREADINFO_GFP,
                                                THREAD_SIZE_ORDER));
-        memset(&irqctx->tinfo, 0, sizeof(struct thread_info));
-        irqctx->tinfo.cpu               = cpu;
-        irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
+        per_cpu(hardirq_stack, cpu) = irqstk;
 
-        per_cpu(hardirq_ctx, cpu) = irqctx;
-
-        irqctx = page_address(alloc_pages_node(cpu_to_node(cpu),
+        irqstk = page_address(alloc_pages_node(cpu_to_node(cpu),
                                                THREADINFO_GFP,
                                                THREAD_SIZE_ORDER));
-        memset(&irqctx->tinfo, 0, sizeof(struct thread_info));
-        irqctx->tinfo.cpu               = cpu;
-        irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);
-
-        per_cpu(softirq_ctx, cpu) = irqctx;
+        per_cpu(softirq_stack, cpu) = irqstk;
 
         printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
-               cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
+               cpu, per_cpu(hardirq_stack, cpu),  per_cpu(softirq_stack, cpu));
 }
 
 void do_softirq_own_stack(void)
 {
-        struct thread_info *curctx;
-        union irq_ctx *irqctx;
+        struct thread_info *curstk;
+        struct irq_stack *irqstk;
         u32 *isp, *prev_esp;
 
-        curctx = current_thread_info();
-        irqctx = __this_cpu_read(softirq_ctx);
-        irqctx->tinfo.task = curctx->task;
+        curstk = current_stack();
+        irqstk = __this_cpu_read(softirq_stack);
 
         /* build the stack frame on the softirq stack */
-        isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));
+        isp = (u32 *) ((char *)irqstk + sizeof(*irqstk));
 
         /* Push the previous esp onto the stack */
-        prev_esp = (u32 *) ((char *)irqctx + sizeof(struct thread_info) -
-                            sizeof(long));
+        prev_esp = (u32 *)irqstk;
         *prev_esp = current_stack_pointer;
 
         call_on_stack(__do_softirq, isp);
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 0de43e98ce08..7bc86bbe7485 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -314,6 +314,10 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
          */
         arch_end_context_switch(next_p);
 
+        this_cpu_write(kernel_stack,
+                  (unsigned long)task_stack_page(next_p) +
+                  THREAD_SIZE - KERNEL_STACK_OFFSET);
+
         /*
          * Restore %gs if needed (which is common)
          */
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index f352a7cc43a1..678c0ada3b3c 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -189,7 +189,7 @@ unsigned long kernel_stack_pointer(struct pt_regs *regs)
         if (context == (sp & ~(THREAD_SIZE - 1)))
                 return sp;
 
-        prev_esp = (u32 *)(context + sizeof(struct thread_info) - sizeof(long));
+        prev_esp = (u32 *)(context);
         if (prev_esp)
                 return (unsigned long)prev_esp;
 
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index a32da804252e..867d53ea88a3 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -758,10 +758,10 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
 #else
         clear_tsk_thread_flag(idle, TIF_FORK);
         initial_gs = per_cpu_offset(cpu);
+#endif
         per_cpu(kernel_stack, cpu) =
                 (unsigned long)task_stack_page(idle) -
                 KERNEL_STACK_OFFSET + THREAD_SIZE;
-#endif
         early_gdt_descr.address = (unsigned long)get_cpu_gdt_table(cpu);
         initial_code = (unsigned long)start_secondary;
         stack_start  = idle->thread.sp;