linux中断导读之--初始化<2>
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继续上一篇，看一下中断向量表初始化部分：
代码在init/main.c-start_kernel/setup_arch(&command_line);
early_trap_init
调用arch/arm/kernel/traps.c中
void __init early_trap_init(void)
{
#if defined(CONFIG_CPU_USE_DOMAINS)
unsigned long vectors = CONFIG_VECTORS_BASE; //可以配置trap基地址
#else
unsigned long vectors = (unsigned long)vectors_page;
#endif
extern char __stubs_start[], __stubs_end[];
extern char __vectors_start[], __vectors_end[];
extern char __kuser_helper_start[], __kuser_helper_end[];
int kuser_sz = __kuser_helper_end - __kuser_helper_start;
/*
* Copy the vectors, stubs and kuser helpers (in entry-armv.S)
* into the vector page, mapped at 0xffff0000, and ensure these
* are visible to the instruction stream.
*/
//将entry-armv.s对应部分copy到该地址，
memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
memcpy((void *)vectors + 0x200, __stubs_start, __stubs_end - __stubs_start);
memcpy((void *)vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);
/*
* Do processor specific fixups for the kuser helpers
*/
kuser_get_tls_init(vectors);
/*
* Copy signal return handlers into the vector page, and
* set sigreturn to be a pointer to these.
*/
memcpy((void *)(vectors + KERN_SIGRETURN_CODE - CONFIG_VECTORS_BASE),
sigreturn_codes, sizeof(sigreturn_codes));
memcpy((void *)(vectors + KERN_RESTART_CODE - CONFIG_VECTORS_BASE),
syscall_restart_code, sizeof(syscall_restart_code));
flush_icache_range(vectors, vectors + PAGE_SIZE);
modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
}
#在arch/arm/kernel/entry-armv.s中
__vectors_start:
ARM( swi SYS_ERROR0 )
THUMB( svc #0 )
THUMB( nop ) //复位
W(b) vector_und + stubs_offset //未定义模式
W(ldr) pc, .LCvswi + stubs_offset //swi，系统调用进入
W(b) vector_pabt + stubs_offset //指令预取
W(b) vector_dabt + stubs_offset //data
W(b) vector_addrexcptn + stubs_offset //reserve
W(b) vector_irq + stubs_offset //irq
W(b) vector_fiq + stubs_offset //fiq，没有用到
.globl __vectors_end
__vectors_end:
.equ stubs_offset, __vectors_start + 0x200 - __stubs_start
#先看宏：
/*
* Vector stubs.
*
* This code is copied to 0xffff0200 so we can use branches in the
* vectors, rather than ldr's. Note that this code must not
* exceed 0x300 bytes.
*
* Common stub entry macro:
* Enter in IRQ mode, spsr = SVC/USR CPSR, lr = SVC/USR PC
*
* SP points to a minimal amount of processor-private memory, the address
* of which is copied into r0 for the mode specific abort handler.
*/
.macro vector_stub, name, mode, correction=0
.align 5
vector_\name:
.if \correction
sub lr, lr, #\correction
.endif
@
@ Save r0, lr_<exception> (parent PC) and spsr_<exception>
@ (parent CPSR)
@
stmia sp, {r0, lr} @ save r0, lr
mrs lr, spsr
str lr, [sp, #8] @ save spsr
@
@ Prepare for SVC32 mode. IRQs remain disabled.
@
mrs r0, cpsr
eor r0, r0, #(\mode ^ SVC_MODE | PSR_ISETSTATE)
msr spsr_cxsf, r0
@
@ the branch table must immediately follow this code
@
and lr, lr, #0x0f
THUMB( adr r0, 1f )
THUMB( ldr lr, [r0, lr, lsl #2] )
mov r0, sp
ARM( ldr lr, [pc, lr, lsl #2] )
movs pc, lr @ branch to handler in SVC mode
/*
* Interrupt dispatcher
*/
vector_stub irq, IRQ_MODE, 4
.long __irq_usr @ 0 (USR_26 / USR_32)
.long __irq_invalid @ 1 (FIQ_26 / FIQ_32)
.long __irq_invalid @ 2 (IRQ_26 / IRQ_32)
.long __irq_svc @ 3 (SVC_26 / SVC_32)
.long __irq_invalid @ 4
.long __irq_invalid @ 5
.long __irq_invalid @ 6
.long __irq_invalid @ 7
.long __irq_invalid @ 8
.long __irq_invalid @ 9
.long __irq_invalid @ a
.long __irq_invalid @ b
.long __irq_invalid @ c
.long __irq_invalid @ d
.long __irq_invalid @ e
.long __irq_invalid @ f
#代进去可以得到：
vector_irq:
.if 4
sub lr, lr, #4
.endif
@
@ Save r0, lr_<exception> (parent PC) and spsr_<exception>
@ (parent CPSR)
@
stmia sp, {r0, lr} @ save r0, lr
mrs lr, spsr
str lr, [sp, #8] @ save spsr
@
@ Prepare for SVC32 mode. IRQs remain disabled.
@
mrs r0, cpsr
eor r0, r0, #(\IRQ_MODE ^ SVC_MODE | PSR_ISETSTATE)
msr spsr_cxsf, r0
@
@ the branch table must immediately follow this code
@
and lr, lr, #0x0f
THUMB( adr r0, 1f )
THUMB( ldr lr, [r0, lr, lsl #2] )
mov r0, sp
ARM( ldr lr, [pc, lr, lsl #2] ) @如果进入中断前是usr，
则取出PC+4*0的内容，即__irq_usr @如果进入中断前 是svc，则取出PC+4*3的内容，即__irq_svc
@根据进入前的状态判断进入哪个处理流程
movs pc, lr @ branch to handler in SVC mode
ENDPROC(vector_irq)
=================
usr_entry
kuser_cmpxchg_check
irq_handler
get_thread_info tsk @得到当前进程信息
mov why, #0
b ret_to_user_from_irq
=================
/*
* Interrupt handling.
*/
.macro irq_handler
#ifdef CONFIG_MULTI_IRQ_HANDLER
ldr r1, =handle_arch_irq
mov r0, sp
ldr r1, [r1]
adr lr, BSYM(9997f)
teq r1, #0
movne pc, r1
#endif
arch_irq_handler_default
9997:
.endm
=================
###arch/arm/kernel/setup.c
handle_arch_irq = mdesc->handle_irq;
####arch/arm/include/asm/entry-macro-multi.s
/*
* Interrupt handling. Preserves r7, r8, r9
*/
.macro arch_irq_handler_default
get_irqnr_preamble r6, lr
1: get_irqnr_and_base r0, r2, r6, lr //******取得中断号，根据平台相关中断状态寄存器地址
movne r1, sp
@
@ routine called with r0 = irq number, r1 = struct pt_regs *
@
adrne lr, BSYM(1b)
bne asm_do_IRQ
##arm/kernel/irq.c
继续##arm/kernel/irq.c
/*
* asm_do_IRQ is the interface to be used from assembly code.
*/
asmlinkage void __exception_irq_entry
asm_do_IRQ(unsigned int irq, struct pt_regs *regs)
{
handle_IRQ(irq, regs);
}
/*
* handles all hardware IRQ's. Decoded IRQs should
* not come via this function. Instead, they should provide their
* own 'handler'. Used by platform code implementing C-based 1st
* level decoding.
*/
void handle_IRQ(unsigned int irq, struct pt_regs *regs)
{
struct pt_regs *old_regs = set_irq_regs(regs);
irq_enter();
/*
* Some hardware gives randomly wrong interrupts. Rather
* than crashing, do something sensible.
*/
if (unlikely(irq >= nr_irqs)) {
if (printk_ratelimit())
printk(KERN_WARNING "Bad IRQ%u\n", irq);
ack_bad_irq(irq);
} else {
generic_handle_irq(irq);
}
/* AT91 specific workaround */
irq_finish(irq);
irq_exit();
set_irq_regs(old_regs);
}
#kernel/irq/irqdesc.c
/**
* generic_handle_irq - Invoke the handler for a particular irq
* @irq: The irq number to handle
*
*/
int generic_handle_irq(unsigned int irq)
{
struct irq_desc *desc = irq_to_desc(irq);
if (!desc)
return -EINVAL;
generic_handle_irq_desc(irq, desc);
return 0;
}
EXPORT_SYMBOL_GPL(generic_handle_irq);
#include/linux/irqdesc.h
static inline void generic_handle_irq_desc(unsigned int irq, struct irq_desc *desc)
{
desc->handle_irq(irq, desc);
}