IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

[linux-2.6-block.git] / arch / i386 / kernel / irq.c

/*
 *	linux/arch/i386/kernel/irq.c
 *
 *	Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
 *
 * This file contains the lowest level x86-specific interrupt
 * entry, irq-stacks and irq statistics code. All the remaining
 * irq logic is done by the generic kernel/irq/ code and
 * by the x86-specific irq controller code. (e.g. i8259.c and
 * io_apic.c.)
 */

#include <asm/uaccess.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/delay.h>

DEFINE_PER_CPU(irq_cpustat_t, irq_stat) ____cacheline_internodealigned_in_smp;
EXPORT_PER_CPU_SYMBOL(irq_stat);

#ifndef CONFIG_X86_LOCAL_APIC
/*
 * 'what should we do if we get a hw irq event on an illegal vector'.
 * each architecture has to answer this themselves.
 */
void ack_bad_irq(unsigned int irq)
{
	printk("unexpected IRQ trap at vector %02x\n", irq);
}
#endif

#ifdef CONFIG_4KSTACKS
/*
 * 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] __read_mostly;
static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
#endif

/*
 * do_IRQ handles all normal device IRQ's (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */
fastcall unsigned int do_IRQ(struct pt_regs *regs)
{	
	struct pt_regs *old_regs;
	/* high bit used in ret_from_ code */
	int irq = ~regs->orig_eax;
	struct irq_desc *desc = irq_desc + irq;
#ifdef CONFIG_4KSTACKS
	union irq_ctx *curctx, *irqctx;
	u32 *isp;
#endif

	if (unlikely((unsigned)irq >= NR_IRQS)) {
		printk(KERN_EMERG "%s: cannot handle IRQ %d\n",
					__FUNCTION__, irq);
		BUG();
	}

	old_regs = set_irq_regs(regs);
	irq_enter();
#ifdef CONFIG_DEBUG_STACKOVERFLOW
	/* Debugging check for stack overflow: is there less than 1KB free? */
	{
		long esp;

		__asm__ __volatile__("andl %%esp,%0" :
					"=r" (esp) : "0" (THREAD_SIZE - 1));
		if (unlikely(esp < (sizeof(struct thread_info) + STACK_WARN))) {
			printk("do_IRQ: stack overflow: %ld\n",
				esp - sizeof(struct thread_info));
			dump_stack();
		}
	}
#endif

#ifdef CONFIG_4KSTACKS

	curctx = (union irq_ctx *) current_thread_info();
	irqctx = hardirq_ctx[smp_processor_id()];

	/*
	 * this is where we switch to the IRQ stack. However, if we are
	 * already using the IRQ stack (because we interrupted a hardirq
	 * handler) we can't do that and just have to keep using the
	 * current stack (which is the irq stack already after all)
	 */
	if (curctx != irqctx) {
		int arg1, arg2, ebx;

		/* 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;