ARM Linux中断机制分析

@ We are now ready to fill in the remaining blanks on the stack:

@

@ r4 - lr_, already fixed up for correct return/restart

@ r5 - spsr_

@ r6 - orig_r0 (see pt_regs definition in ptrace.h)

@

@ Also, separately save sp_usr and lr_usr

@

stmia r0, {r4 - r6}//stmia将svc模式下的寄存器r4-r6保存到ARM_pc，ARM_cpsr和

ARM_ORIG_r0,显然ARM_ORIG_r0保存了-1（r6）这个常量

ARM( stmdb r0, {sp, lr}^ )//stmdb指令的^标志表示存储发生中断的模式下的sp,lr寄存器

到ARM_sp和ARM_lr中。

THUMB( store_user_sp_lr r0, r1, S_SP - S_PC )

@ Enable the alignment trap while in kernel mode

alignment_trap r0//alignment_trap在配置CONFIG_ALIGNMENT_TRAP时有效，如果开启了该选

//项，中断处理中将支持对齐跟踪

@ Clear FP to mark the first stack frame

zero_fp//zero_fp用来设置fp栈帧寄存器为0

#ifdef CONFIG_IRQSOFF_TRACER

bl trace_hardirqs_off

#endif

.endm@usr_entry宏定义结束

arch/arm/kernel/entry-header.S

.macroget_thread_info, rd

mov \rd, sp, lsr #13

mov \rd, \rd, lsl #13

.endm

linux/arch/arm/kernel/entry-armv.S

/*

* Interrupt handling. Preserves r7, r8, r9

*/

.macroirq_handler

#ifdef CONFIG_MULTI_IRQ_HANDLER

ldr r5, =handle_arch_irq

mov r0, sp

ldr r5, [r5]

adr lr, BSYM(9997f)

teq r5, #0

movne pc, r5

#endif

arch_irq_handler_default

9997:

.endm

arch/arm/include/asm/entry_macro_multi.S

/*

* Interrupt handling. Preserves r7, r8, r9

*/

.macroarch_irq_handler_default //get_irqnr_preamble用来获取中断状态寄存器基地址

get_irqnr_preamble r5, lr//将中断控制器的状态寄存器的地址存储到r5

1: get_irqnr_and_base r0, r6, r5, lr//判断中断号，通过r0返回

movne r1, sp//如果还存在中断，就将sp作为第二个参数，调用asm_do_IRQ。sp目前指向pt_regs

@

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

@

adrne lr, BSYM(1b)//这里将lr设置为get_irqnr_and_base的第二条指令，因为第二次循环时，不必执行其第一条指令(加载寄存器基址)

bne asm_do_IRQ //将中断号、pt_regs(中断前的寄存器现场)传递给asm_do_IRQ。asm_do_IRQ返回时，

//会返回到get_irqnr_and_base处，直到所有中断都已经处理完毕才退出循环。

#ifdef CONFIG_SMP//针对SMP