系统调用格式
SWI + offset+ 系统调用号
参数 R0，R1，R2
.text
.align 2
.global main
main:
adr r1, msg @ address
mov r0, #1 @ stdout
mov r2, #13 @ length
swi #0x900004 @ sys_write
mov r0, #0
swi #0x900001 @ sys_exit
.align 2
msg:
.asciz "hello, world\n"
//系统调用汇编参数传递格式 include\asm-arm\unistd.h
#define __syscall_return(type, res) \
do { \
if ((unsigned long)(res) >= (unsigned long)(-MAX_ERRNO)) { \
errno = -(res); \
res = -1; \
} \
return (type) (res); \
} while (0)
#define _syscall0(type,name) \
type name(void) { \
__SYS_REG(name) \
register long __res_r0 __asm__("r0"); \
long __res; \
__asm__ __volatile__ ( \
__syscall(name) \
: "=r" (__res_r0) \
: __SYS_REG_LIST() \
: "memory" ); \
__res = __res_r0; \
__syscall_return(type,__res); \
}
#define _syscall1(type,name,type1,arg1) \
type name(type1 arg1) { \
__SYS_REG(name) \
register long __r0 __asm__("r0") = (long)arg1; \
register long __res_r0 __asm__("r0"); \
long __res; \
__asm__ __volatile__ ( \
__syscall(name) \
: "=r" (__res_r0) \
: __SYS_REG_LIST( "0" (__r0) ) \
: "memory" ); \
__res = __res_r0; \
__syscall_return(type,__res); \
}
#define _syscall2(type,name,type1,arg1,type2,arg2) \
type name(type1 arg1,type2 arg2) { \
__SYS_REG(name) \
register long __r0 __asm__("r0") = (long)arg1; \
register long __r1 __asm__("r1") = (long)arg2; \
register long __res_r0 __asm__("r0"); \
long __res; \
__asm__ __volatile__ ( \
__syscall(name) \
: "=r" (__res_r0) \
: __SYS_REG_LIST( "0" (__r0), "r" (__r1) ) \
: "memory" ); \
__res = __res_r0; \
__syscall_return(type,__res); \
}
#define _syscall3(type,name,type1,arg1,type2,arg2,type3,arg3) \
type name(type1 arg1,type2 arg2,type3 arg3) { \
__SYS_REG(name) \
register long __r0 __asm__("r0") = (long)arg1; \
register long __r1 __asm__("r1") = (long)arg2; \
register long __r2 __asm__("r2") = (long)arg3; \
register long __res_r0 __asm__("r0"); \
long __res; \
__asm__ __volatile__ ( \
__syscall(name) \
: "=r" (__res_r0) \
: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2) ) \
: "memory" ); \
__res = __res_r0; \
__syscall_return(type,__res); \
}
#define _syscall4(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4)\
type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4) { \
__SYS_REG(name) \
register long __r0 __asm__("r0") = (long)arg1; \
register long __r1 __asm__("r1") = (long)arg2; \
register long __r2 __asm__("r2") = (long)arg3; \
register long __r3 __asm__("r3") = (long)arg4; \
register long __res_r0 __asm__("r0"); \
long __res; \
__asm__ __volatile__ ( \
__syscall(name) \
: "=r" (__res_r0) \
: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2), "r" (__r3) ) \
: "memory" ); \
__res = __res_r0; \
__syscall_return(type,__res); \
}
#define _syscall5(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4,type5,arg5) \
type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4, type5 arg5) { \
__SYS_REG(name) \
register long __r0 __asm__("r0") = (long)arg1; \
register long __r1 __asm__("r1") = (long)arg2; \
register long __r2 __asm__("r2") = (long)arg3; \
register long __r3 __asm__("r3") = (long)arg4; \
register long __r4 __asm__("r4") = (long)arg5; \
register long __res_r0 __asm__("r0"); \
long __res; \
__asm__ __volatile__ ( \
__syscall(name) \
: "=r" (__res_r0) \
: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2), \
"r" (__r3), "r" (__r4) ) \
: "memory" ); \
__res = __res_r0; \
__syscall_return(type,__res); \
}
#define _syscall6(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4,type5,arg5,type6,arg6) \
type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4, type5 arg5, type6 arg6) { \
__SYS_REG(name) \
register long __r0 __asm__("r0") = (long)arg1; \
register long __r1 __asm__("r1") = (long)arg2; \
register long __r2 __asm__("r2") = (long)arg3; \
register long __r3 __asm__("r3") = (long)arg4; \
register long __r4 __asm__("r4") = (long)arg5; \
register long __r5 __asm__("r5") = (long)arg6; \
register long __res_r0 __asm__("r0"); \
long __res; \
__asm__ __volatile__ ( \
__syscall(name) \
: "=r" (__res_r0) \
: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2), \
"r" (__r3), "r" (__r4), "r" (__r5) ) \
: "memory" ); \
__res = __res_r0; \
__syscall_return(type,__res); \
