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标题: linux下X86架构IDT解析(4) [打印本页]

作者: yuyang911220 时间: 2015-7-30 18:57 标题: linux下X86架构IDT解析(4)

769

770

#ifdef CONFIG_X86_32771

set_system_trap_gate(SYSCALL_VECTOR, &system_call);772

set_bit(SYSCALL_VECTOR, used_vectors);773

#endif774

775

/*776

* Set the IDT descriptor to a fixed read-only location, so that
* the "sidt" instruction will not leak the location of the kernel, and
778

* to defend the IDT against arbitrary memory write vulnerabilities.779

* It will be reloaded in cpu_init() */780

__set_fixmap(FIX_RO_IDT, __pa_symbol(idt_table), PAGE_KERNEL_RO);781

idt_descr.address = fix_to_virt(FIX_RO_IDT);782

783

/*784

* Should be a barrier for any external CPU state:785

*/786

cpu_init();787

788

x86_init.irqs.trap_init();789

795

}
3.对剩余表项的初始化由init_IRQ()完成。init_IRQ()通过调用native_init_IRQ()函数完成初始化。
void __init
native_init_IRQ(void)193

{194

int i;195

196

/* Execute any quirks before the call gates are initialised: */197

x86_init.irqs.pre_vector_init();198

199

apic_intr_init();200

201

/*202

* Cover the whole vector space, no vector can escape203

* us. (some of these will be overridden and become204

* 'special' SMP interrupts)205

*/206

i = FIRST_EXTERNAL_VECTOR;207

for_each_clear_bit_from(i, used_vectors, NR_VECTORS) {
/* IA32_SYSCALL_VECTOR could be used in trap_init already. */
209

set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);210

}211

212

if (!acpi_ioapic && !of_ioapic)213

setup_irq(2, &irq2);214

215

#ifdef CONFIG_X86_32216

irq_ctx_init(smp_processor_id());217

#endif218

} 可以看出调用set_intr_gate()将剩下的233项全部初始化为中断门。其中的NR_VECTOR为256，FIRST_EXTERNAL_VECTOR为0x20(也就是32)，所以循环共进行224次，其中当要初始化的中断号等于SYSCALL_VECTOR(系统调用中断号)时，就跳过，所以也就是前面说的初始化剩下的223项。现在的关键是给这些中断的处理程序是什么？这又要说到interrupt数组了。该数组定义在arch/x86_64/kernel/i8259.c中：
#define IRQ(x,y)
IRQ##x##y##_interrupt

#define IRQLIST_16(x) \

IRQ(x,0), IRQ(x,1), IRQ(x,2), IRQ(x,3), \

IRQ(x,4), IRQ(x,5), IRQ(x,6), IRQ(x,7), \

IRQ(x,8), IRQ(x,9), IRQ(x,a), IRQ(x,b), \

IRQ(x,c), IRQ(x,d), IRQ(x,e), IRQ(x,f)

/* for the irq vectors */

static void (*interrupt[NR_VECTORS - FIRST_EXTERNAL_VECTOR])(void) = {

IRQLIST_16(0x2), IRQLIST_16(0x3),

IRQLIST_16(0x4), IRQLIST_16(0x5), IRQLIST_16(0x6), IRQLIST_16(0x7),

IRQLIST_16(0x8), IRQLIST_16(0x9), IRQLIST_16(0xa), IRQLIST_16(0xb),

IRQLIST_16(0xc), IRQLIST_16(0xd), IRQLIST_16(0xe), IRQLIST_16(0xf)

};
现在结合native_init_IRQ()分析一下。当进行第一次循环也就是i=0的时候，vector=32，所以set_intr_gate()的调用是:
set_intr_gate(32,interrupt[0]);
对应的是：

IRQLIST_16(0x2)
--->IRQ(0x2,0)

|--->IRQ0x20_interrupt()
这样就将IRQ0x20_interrupt()设置为0x20中断的处理程序了。
下来我们看看这些IRQn_interrupt()(n=0x20~0xff)是如何建立的。
#define BUILD_IRQ(nr) \
asmlinkage void IRQ_NAME(nr); \
__asm__( \
"\n.p2align\n" \
"IRQ" #nr "_interrupt:\n\t" \
"push $~(" #nr ") ; " \
"jmp common_interrupt");
common_interrupt是一个汇编标号，在它里面会调用do_IRQ()函数去处理中断。

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