=> create_thread (struct pthread *pd, const struct pthread_attr

*attr,STACK_VARIABLES_PARMS)

3. create_thread (struct pthread *pd, const struct pthread_attr *attr,STACK_VARIABLES_PARMS)

* pd :

pthread_t *tid  =>  ALLOCATE_STACK  分配并初始化

* attr:

default_attr

* STACK_VARIABLES_PARMS:

user thread stack (pd -1)

=> int res = do_clone (pd, attr, clone_flags, start_thread,STACK_VARIABLES_ARGS, 1);

4. static int do_clone (struct pthread *pd, const struct pthread_attr *attr,

int clone_flags, int (*fct) (void *), STACK_VARIABLES_PARMS, int stopped)

* clone_flags:

int clone_flags = (CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGNAL

| CLONE_SETTLS | CLONE_PARENT_SETTID

| CLONE_CHILD_CLEARTID | CLONE_SYSVSEM

* fct ：

start_thread => /* Run the code the user provided.  */

THREAD_SETMEM (pd, result, pd->start_routine (pd->arg));

* stopped

* 其他同上

=> ARCH_CLONE (fct, STACK_VARIABLES_ARGS, clone_flags,

pd, &pd->tid, TLS_VALUE, &pd->tid)

5.  ENTRY(__clone) :

int clone(int (*fn)(void *arg), void *child_stack, int flags, void *arg,

pid_t *ptid, struct user_desc *tls, pid_t *ctid);

R0 => fct (start_thread ,function pointer)

R1 => STACK_VARIABLES_ARGS (user thread stack pointer)

R2 => clone_flags

R3 => pd  (pthead pointer)

user sp => &pd->tid      (ptid pointer)

user sp -4 => TLS_VALUE  (pd+1, tls start addr)

user sp -8 => &pd->tid      (ctid pointer)

R0 <= R2  (clone_flags)

R1 <= R1  STACK_VARIABLES_ARGS (user thread stack pointer)

R2 <= user sp  (ptid pointer)

R3 <= user sp -4 (TLS_VALUE)

R4 <= user sp -8  (ctid pointer)

=> R7 <= sys_clone_wrapper (120)

swi 0

user :

-----------------------------------------------------------------------------------

kernel :

1.     ENTRY(vector_swi)

* 开始构建 c 函数 sys_clone的栈:

High addr:

(FD 栈)

|    ......          |

|--------------------|

上次user sp --->  |    xxxx            |

|--------------------|

ARM_ORIG_r0 --->  |    R0              |

|--------------------|                                          A

ARM_cpsr    --->  |    spsr            |      swi 前的cpsr (user 下的)            |

|--------------------|                                          |

ARM_pc      --->  | swi 指令下一条地址 |                                 #S_FRAME_SIZE

|--------------------|                                          |

ARM_lr      --->  |    LR_usermode     |                                          |

|--------------------|                                          |

ARM_sp      --->  |    SP_usermode     |                                          |

|--------------------|                                          |

ARM_ip      --->  |     R12            |       R12-R1                             |

|     ...            |                                          |

|     ...            |                                          |

ARM_r1      --->  |     R1             |                                          |

|--------------------|                                          V

ARM_r0      --->  |     R0             |

|--------------------|

syscall参数6--->  |    R5              |

|--------------------|

syscall参数5--->  |    R4              |

|--------------------|

Low addr

根据上面的栈

a. syscall 时kernel 栈上ARM_r0和ARM_ORIG_r0 看起来是一样的内容

其他异常不一样

b.  syscall 最大参数 6个放到R0-R5,在具体call kernel 函数前,总认为

传了6个,所以按规则 参数1-4放 R0-R1, 参数5,6压栈

* 根据 scno (R7) 查表到sys_clone_wrapper跳转执行

cmp scno, #NR_syscalls  @ check upper syscall limit

adr lr, ret_fast_syscall  @ return address   @ 注意返回到ret_fast_syscall

在执行完　sys_clone_wrapper后

ldrcc  pc, [tbl, scno, lsl #2]  @ call sys_* routine

2.  sys_clone_wrapper

因为sys clone 没有6个参数,所以根据时间情况调整 上面的栈:

ARM_r0      --->  |   上面不变　       |

|--------------------|

syscall参数--->  |  pt_regs *         |   从R5 改变为上面 pt_regs 所指地址

|--------------------|

syscall参数5--->  |    R4              |

|--------------------|

3.  执行　c 函数　sys_clone:

int sys_clone(unsigned long clone_flags(R0), unsigned long newsp(R1),

int __user *parent_tidptr(R2), int tls_val(R3),

int __user *child_tidptr(svc sp), struct pt_regs *regs (svc sp-4))

4. sys_clone 返回 执行　ret_fast_syscall

如果没有发生调度,那么

恢复swi 前所有用户上下文,并获取 arm_pc (值为swi 0下面那句)

栈如下:

|    ......          |

|--------------------|

上次user sp --->  |    xxxx            |

|--------------------|

下面的部分全部出栈了