linux-2.6.26內(nèi)核中ARM中斷實(shí)現(xiàn)詳解(2)

作者：時(shí)間：2012-08-21 來源：網(wǎng)絡(luò)

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@ r2 - lr_, already fixed up for correct return/restart

@ r3 - spsr_

@ r4 - orig_r0 (see pt_regs definition in ptrace.h)

@ Also, separately save sp_usr and lr_usr

stmia r0, {r2 - r4}

stmdb r0, {sp, lr}^

@ Enable the alignment trap while in kernel mode

alignment_trap r0

@ Clear FP to mark the first stack frame

zero_fp

.endm

上面的這段代碼主要在填充結(jié)構(gòu)體pt_regs ，這里提到的struct pt_regs，在include/asm/ptrace.h中定義。此時(shí)sp指向struct pt_regs。

struct pt_regs {

long uregs[18];

};

#define ARM_cpsr uregs[16]

#define ARM_pc uregs[15]

#define ARM_lr uregs[14]

#define ARM_sp uregs[13]

#define ARM_ip uregs[12]

#define ARM_fp uregs[11]

#define ARM_r10 uregs[10]

#define ARM_r9 uregs[9]

#define ARM_r8 uregs[8]

#define ARM_r7 uregs[7]

#define ARM_r6 uregs[6]

#define ARM_r5 uregs[5]

#define ARM_r4 uregs[4]

#define ARM_r3 uregs[3]

#define ARM_r2 uregs[2]

#define ARM_r1 uregs[1]

#define ARM_r0 uregs[0]

#define ARM_ORIG_r0 uregs[17]

3.4 irq_handler的實(shí)現(xiàn)過程，archarmkernelentry-armv.S

.macro irq_handler

get_irqnr_preamble r5, lr

@在include/asm/arch-s3c2410/entry-macro.s中定義了宏get_irqnr_preamble為空操作，什么都不做

1: get_irqnr_and_base r0, r6, r5, lr @判斷中斷號(hào)，通過R0返回，3.5節(jié)有實(shí)現(xiàn)過程

movne r1, sp

@ routine called with r0 = irq number, r1 = struct pt_regs *

adrne lr, 1b

bne asm_do_IRQ @進(jìn)入中斷處理。

……

.endm

3.5 get_irqnr_and_base中斷號(hào)判斷過程，include/asm/arch-s3c2410/entry-macro.s

.macro get_irqnr_and_base, irqnr, irqstat, base, tmp

mov base, #S3C24XX_VA_IRQ

@@ try the interrupt offset register, since it is there

ldr irqstat, [ base, #INTPND ]

teq irqstat, #0

beq 1002f

ldr irqnr, [ base, #INTOFFSET ] @通過判斷INTOFFSET寄存器得到中斷位置

mov tmp, #1

tst irqstat, tmp, lsl irqnr

bne 1001f

@@ the number specified is not a valid irq, so try

@@ and work it out for ourselves

mov irqnr, #0 @@ start here

@@ work out which irq (if any) we got

movs tmp, irqstat, lsl#16

addeq irqnr, irqnr, #16

moveq irqstat, irqstat, lsr#16

tst irqstat, #0xff

addeq irqnr, irqnr, #8

moveq irqstat, irqstat, lsr#8

tst irqstat, #0xf

addeq irqnr, irqnr, #4

moveq irqstat, irqstat, lsr#4

tst irqstat, #0x3

addeq irqnr, irqnr, #2

moveq irqstat, irqstat, lsr#2

tst irqstat, #0x1

addeq irqnr, irqnr, #1

@@ we have the value

1001:

adds irqnr, irqnr, #IRQ_EINT0 @加上中斷號(hào)的基準(zhǔn)數(shù)值，得到最終的中斷號(hào)，注意：此時(shí)沒有考慮子中斷的具體情況，(子中斷的問題后面會(huì)有講解)。IRQ_EINT0在include/asm/arch-s3c2410/irqs.h中定義.從這里可以看出，中斷號(hào)的具體值是有平臺(tái)相關(guān)的代碼決定的，和硬件中斷掛起寄存器中的中斷號(hào)是不等的。

1002:

@@ exit here, Z flag unset if IRQ

.endm

3.6 asm_do_IRQ實(shí)現(xiàn)過程，arch/arm/kernel/irq.c

asmlinkage void __exception asm_do_IRQ(unsigned int irq, struct pt_regs *regs)

{

struct pt_regs *old_regs = set_irq_regs(regs);

struct irq_desc *desc = irq_desc + irq;//根據(jù)中斷號(hào)找到對(duì)應(yīng)的irq_desc

* Some hardware gives randomly wrong interrupts. Rather

* than crashing, do something sensible.

if (irq >= NR_IRQS)

desc = bad_irq_desc;