Android(安卓)系统调用

另外： http://hamer-blog.logdown.com/posts/174690-android-find-kernel-headers-the-source-needs

http://blog.csdn.net/heqiangflytosky/article/details/8941466

http://www.eoeandroid.com/thread-4668-1-1.html

http://blog.chinaunix.net/uid-9078996-id-2010323.html

http://blog.csdn.net/andyhuabing/article/details/7183369

1、Syscall stub：

每个系统调用函数都由一个小的汇编代码段实现(称为”syscall stub”),这是由tools/gensyscalls.py工具自动生成的，它从SYSCALL.TXT中取得输入参数。
SYSCALLS.TXT包含了一份要生成的系统调用块列表，和相应的系统调用数字标识符（ARM和X86不一样），以及它的签署。
如果你要修改这个文件，你可能要使用tools/checksyscalls.py工具，检查它里面是否包含官方linux核心头文件，如果有不合法的syscall ids，它会报告错误。
有时，C库函数其实就是一个包装，它内部调用相应的syscall名称，例如，exit函数由C库提供，它调用了_exit()这个syscall stub.
详细内容请参考SYSCALLS.TXT文件。

2、比如要增加消息队列的函数：
(1). 修改 SYSCALL.TXT
增加：
long ipc(unsigned int call, int first, unsigned long second, unsigned long third, void __user *ptr, long fifth) 117
(2). 执行 tools/gensyscalls.py
(3). 以下内容会由 tools/gensyscalls.py 自动产生：

bionic/libc/arch-mips/syscalls.mk
----------------------------------------------------------------------------------------------------------------------------
syscall_src += arch-mips/syscalls/ipc.S
----------------------------------------------------------------------------------------------------------------------------

bionic/libc/include/sys/linux-syscalls.h
----------------------------------------------------------------------------------------------------------------------------
#define _NR_ipc (_NR_SYSCALL_BASE + 117)
----------------------------------------------------------------------------------------------------------------------------

bionic/libc/include/sys/linux-unistd.h
----------------------------------------------------------------------------------------------------------------------------
int ipc (unsigned int call, int first, int second, int third, void* ptr, long fifth);
----------------------------------------------------------------------------------------------------------------------------

(4). 手动编写
bionic/libc/Android.mk
----------------------------------------------------------------------------------------------------------------------------
ifeq ($(TARGET_ARCH),mips)
libc_common_src_files += \
arch-mips/bionic/sys_ipc.c \

----------------------------------------------------------------------------------------------------------------------------
bionic/libc/arch-mips/bionic/sys_ipc.c
----------------------------------------------------------------------------------------------------------------------------
[cpp] view plain copy

#include<stdarg.h>
#include<sys/msg.h>
externintipc(unsignedintcall,intfirst,intsecond,intthird,void*ptr,longfifth);
intsemget(key_tkey,intnsems,intsemflg)
{
returnipc(SEMGET,key,nsems,semflg,(void*)NULL,(long)NULL);
}
intsemop(intsemid,structsembuf*sops,size_tnsops)
{
returnipc(SEMOP,semid,(int)nsops,0,sops,(long)NULL);
}
void*shmat(intshmid,constvoid*shmaddr,intshmflg)
{
intrval;
unsignedlongraddr;
rval=ipc(SHMAT,shmid,shmflg,(int)&raddr,(void*)shmaddr,(long)NULL);
if(rval<0)
return(char*)rval;
return(char*)raddr;
}
intshmctl(intshmid,intcmd,structshmid_ds*buf)
{
returnipc(SHMCTL,shmid,cmd,0,buf,(long)NULL);
}
intshmget(key_tkey,size_tsize,intshmflg)
{
returnipc(SHMGET,key,size,shmflg,(void*)NULL,(long)NULL);
}
intmsgctl(intmsqid,intcmd,structmsqid_ds*buf)
{
returnipc(MSGCTL,msqid,cmd,0,buf,(long)NULL);
}
intshmdt(constvoid*shmaddr)
{
returnipc(SHMDT,0,0,0,(void*)shmaddr,(long)NULL);
}
intmsgget(key_tkey,intmsgflg)
{
returnipc(MSGGET,key,msgflg,0,NULL,(long)NULL);
}
ssize_tmsgrcv(intmsqid,void*msgp,size_tmsgsz,longintmsgtyp,intmsgflg)
{
structipc_kludgetmp;
tmp.msgp=msgp;
tmp.msgtyp=msgtyp;
returnipc(MSGRCV,msqid,msgsz,msgflg,&tmp,(long)NULL);
}
intmsgsnd(intmsqid,constvoid*msgp,size_tmsgsz,intmsgflg)
{
returnipc(MSGSND,msqid,msgsz,msgflg,(void*)msgp,(long)NULL);
}

bionic/libc/arch-mips/syscalls/ipc.S
----------------------------------------------------------------------------------------------------------------------------
/* autogenerated by gensyscalls.py */
#include <sys/linux-syscalls.h>
.text
.globl ipc
.align 4
.ent ipc

ipc:
.set noreorder
.cpload $t9
li $v0, __NR_ipc
syscall
bnez $a3, 1f
move $a0, $v0
j $ra
nop
1:
la $t9,__set_errno
j $t9
nop
.set reorder
.end ipc

----------------------------------------------------------------------------------------------------------------------------
bionic/libc/include/sys/msg.h
----------------------------------------------------------------------------------------------------------------------------

[cpp] view plain copy

#ifndef_SYS_MSG_H
#define_SYS_MSG_H
#include<features.h>
#define__need_size_t
#include<stddef.h>
/*GetcommondefinitionofSystemVstyleIPC.*/
#include<sys/ipc.h>
/*Getsystemdependentdefinitionof`structmsqid_ds'andmore.*/
#include<msq.h>
/*Definetypesrequiredbythestandard.*/
#define__need_time_t
#include<time.h>
#ifndef__pid_t_defined
typedef__pid_tpid_t;
#define__pid_t_defined
#endif
#ifndef__ssize_t_defined
typedef__ssize_tssize_t;
#define__ssize_t_defined
#endif
#defineSEMOP1
#defineSEMGET2
#defineSEMCTL3
#defineSEMTIMEDOP4
#defineMSGSND11
#defineMSGRCV12
#defineMSGGET13
#defineMSGCTL14
#defineSHMAT21
#defineSHMDT22
#defineSHMGET23
#defineSHMCTL24
/*ThefollowingSystemVstyleIPCfunctionsimplementamessagequeue
system.ThedefinitionisfoundinXPG2.*/
#ifdef__USE_GNU
/*Templateforstructtobeusedasargumentfor`msgsnd'and`msgrcv'.*/
structmsgbuf
{
longintmtype;/*typeofreceived/sentmessage*/
charmtext[1];/*textofthemessage*/
};
#endif
structipc_kludge{
structmsgbuf__user*msgp;
longmsgtyp;
};
__BEGIN_DECLS
/*Messagequeuecontroloperation.*/
externintmsgctl(int__msqid,int__cmd,structmsqid_ds*__buf);
/*Getmessagesqueue.*/
externintmsgget(key_t__key,int__msgflg);
/*Receivemessagefrommessagequeue.
Thisfunctionisacancellationpointandthereforenotmarkedwith
__THROW.*/
externssize_tmsgrcv(int__msqid,void*__msgp,size_t__msgsz,longint__msgtyp,int__msgflg);
/*Sendmessagetomessagequeue.
Thisfunctionisacancellationpointandthereforenotmarkedwith
__THROW.*/
externintmsgsnd(int__msqid,__constvoid*__msgp,size_t__msgsz,int__msgflg);
__END_DECLS
#endif/*sys/msg.h*/

----------------------------------------------------------------------------------------------------------------------------
Create bionic/libc/include/msq.h

[cpp] view plain copy

#ifndef_SYS_MSG_H
#error"Neveruse<msq.h>directly;include<sys/msg.h>instead."
#endif
#include<sys/types.h>
/*Defineoptionsformessagequeuefunctions.*/
#defineMSG_NOERROR010000/*noerrorifmessageistoobig*/
/*Typesusedinthestructuredefinition.*/
typedefunsignedshortintmsgqnum_t;
typedefunsignedshortintmsglen_t;
/*Structureofrecordforonemessageinsidethekernel.
Thetype`struct__msg'isopaque.*/
structmsqid_ds
{
structipc_permmsg_perm;/*structuredescribingoperationpermission*/
__time_tmsg_stime;/*timeoflastmsgsndcommand*/
__time_tmsg_rtime;/*timeoflastmsgrcvcommand*/
__time_tmsg_ctime;/*timeoflastchange*/
msgqnum_tmsg_qnum;/*numberofmessagescurrentlyonqueue*/
msglen_tmsg_qbytes;/*maxnumberofbytesallowedonqueue*/
__pid_tmsg_lspid;/*pidoflastmsgsnd()*/
__pid_tmsg_lrpid;/*pidoflastmsgrcv()*/
};

更多相关文章

随机推荐