irq_32.c

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/*
 *  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 <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>
#include <linux/uaccess.h>
#include <linux/percpu.h>
#include <linux/mm.h>

#include <asm/apic.h>

DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
EXPORT_PER_CPU_SYMBOL(irq_stat);

DEFINE_PER_CPU(struct pt_regs *, irq_regs);
EXPORT_PER_CPU_SYMBOL(irq_regs);

#ifdef CONFIG_DEBUG_STACKOVERFLOW

int sysctl_panic_on_stackoverflow __read_mostly;

/* Debugging check for stack overflow: is there less than 1KB free? */
static int check_stack_overflow(void)
{
    long sp;

    __asm__ __volatile__("andl %%esp,%0" :
                 "=r" (sp) : "0" (THREAD_SIZE - 1));

    return sp < (sizeof(struct thread_info) + STACK_WARN);
}

static void print_stack_overflow(void)
{
    printk(KERN_WARNING "low stack detected by irq handler\n");
    dump_stack();
    if (sysctl_panic_on_stackoverflow)
        panic("low stack detected by irq handler - check messages\n");
}

#else
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);

static void call_on_stack(void *func, void *stack)
{
    asm volatile("xchgl %%ebx,%%esp \n"
             "call  *%%edi      \n"
             "movl  %%ebx,%%esp \n"
             : "=b" (stack)
             : "0" (stack),
               "D"(func)
             : "memory", "cc", "edx", "ecx", "eax");
}

static inline int
execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq)
{
    union irq_ctx *curctx, *irqctx;
    u32 *isp, arg1, arg2;

    curctx = (union irq_ctx *) current_thread_info();
    irqctx = __this_cpu_read(hardirq_ctx);

    /*
     * 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 (unlikely(curctx == irqctx))
        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;

    /* Copy the preempt_count so that the [soft]irq checks work. */
    irqctx->tinfo.preempt_count = curctx->tinfo.preempt_count;

    if (unlikely(overflow))
        call_on_stack(print_stack_overflow, isp);

    asm volatile("xchgl %%ebx,%%esp \n"
             "call  *%%edi      \n"
             "movl  %%ebx,%%esp \n"
             : "=a" (arg1), "=d" (arg2), "=b" (isp)
             :  "0" (irq),   "1" (desc),  "2" (isp),
            "D" (desc->handle_irq)
             : "memory", "cc", "ecx");
    return 1;
}

/*
 * allocate per-cpu stacks for hardirq and for softirq processing
 */
void __cpuinit irq_ctx_init(int cpu)
{
    union irq_ctx *irqctx;

    if (per_cpu(hardirq_ctx, cpu))
        return;

    irqctx = 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.preempt_count = HARDIRQ_OFFSET;
    irqctx->tinfo.addr_limit    = MAKE_MM_SEG(0);

    per_cpu(hardirq_ctx, cpu) = irqctx;

    irqctx = 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;

    printk(KERN_DEBUG "CPU %u irqstacks, hard=%p soft=%p\n",
           cpu, per_cpu(hardirq_ctx, cpu),  per_cpu(softirq_ctx, cpu));
}

asmlinkage void do_softirq(void)
{
    unsigned long flags;
    struct thread_info *curctx;
    union irq_ctx *irqctx;
    u32 *isp;

    if (in_interrupt())
        return;

    local_irq_save(flags);

    if (local_softirq_pending()) {
        curctx = current_thread_info();
        irqctx = __this_cpu_read(softirq_ctx);
        irqctx->tinfo.task = curctx->task;
        irqctx->tinfo.previous_esp = current_stack_pointer;

        /* build the stack frame on the softirq stack */
        isp = (u32 *) ((char *)irqctx + sizeof(*irqctx));

        call_on_stack(__do_softirq, isp);
        /*
         * Shouldn't happen, we returned above if in_interrupt():
         */
        WARN_ON_ONCE(softirq_count());
    }

    local_irq_restore(flags);
}

bool handle_irq(unsigned irq, struct pt_regs *regs)
{
    struct irq_desc *desc;
    int overflow;

    overflow = check_stack_overflow();

    desc = irq_to_desc(irq);
    if (unlikely(!desc))
        return false;

    if (user_mode_vm(regs) || !execute_on_irq_stack(overflow, desc, irq)) {
        if (unlikely(overflow))
            print_stack_overflow();
        desc->handle_irq(irq, desc);
    }

    return true;
}