Linux中断导读之一--初始化<2>
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