1 files changed, 41 insertions, 42 deletions

diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c
index d7fcbedc9c43..63ce838e5a54 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 +69,26 @@ static void call_on_stack(void *func, void *stack)
                      : "memory", "cc", "edx", "ecx", "eax");
 }
 
+/* how to get the current stack pointer from C */
+#define current_stack_pointer ({                \
+        unsigned long sp;                       \
+        asm("mov %%esp,%0" : "=g" (sp));        \
+        sp;                                     \
+})
+
+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;
-        u32 *isp, arg1, arg2;
+        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
@@ -92,13 +96,14 @@ 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;
-        irqctx->tinfo.previous_esp = current_stack_pointer;
+        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))
                 call_on_stack(print_stack_overflow, isp);
@@ -118,46 +123,40 @@ 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_ctx, cpu) = irqctx;
+        per_cpu(hardirq_stack, cpu) = irqstk;
 
-        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;
-        u32 *isp;
+        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;
-        irqctx->tinfo.previous_esp = current_stack_pointer;
+        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 *)irqstk;
+        *prev_esp = current_stack_pointer;
 
         call_on_stack(__do_softirq, isp);
 }