int copy_thread(unsigned long clone_flags,
unsigned long usp, unsigned long stk_size,
struct task_struct *p, struct pt_regs *regs)
{
unsigned long child_tos = KSTK_TOS(p);
struct pt_regs *childregs;
if(!user_mode(regs)) {
/* kernel thread */
if(usp != 0)
panic("trying to start kernel thread with usp != 0");
/* childregs = full task switch frame on kernel stack of child */
childregs = (struct pt_regs *)(child_tos) - 1;
*childregs = *regs;
childregs->r4 = 0;
regs->r4 = p->pid;
/* return via ret_from_fork */
childregs->lkr = (unsigned long)ret_from_fork;
/* setup ksp/usp */
p->thread.ksp = (unsigned long)childregs - 4; /* perhaps not necessary */
childregs->sp = p->thread.ksp;
p->thread.usp = 0;
p->thread.which_stack = 0; /* kernel stack */
//printk("copy_thread1: ->pid=%d tsp=%lx r5=%lx p->thread.usp=%lx\n",
// p->pid, task_stack_page(p), childregs->r5, p->thread.ksp, p->thread.usp);
} else {
/* userspace thread (vfork, clone) */
unsigned long ra_in_syscall;
struct pt_regs* childsyscallregs;
//asm volatile("break");
/* this was brought to us by sys_tct_vfork in kernel/sys_tct.c */
ra_in_syscall = regs->r1;
/* childsyscallregs = full syscall frame on kernel stack of child */
childsyscallregs = (struct pt_regs *)(child_tos) - 1;
/* no need to return value here, it will be set by task switch frame */
/* copy task switch frame, child shall return with the same register as parent entered the syscall except for return value of syscall */
childregs = childsyscallregs - 1;
/* child shall have same syscall context to restore as parent has */
*childsyscallregs = *regs;
regs->r4 = p->pid; /* parents get child's pid as the retval */
/* user stack pointer is sharef with the parent per definition of vfork */
p->thread.usp = usp;
/* kernel stack pointer is not shared with parent, it is the beginning of the just created new task switch segment on the kernel itself */
p->thread.ksp = (unsigned long)childregs - 4;
p->thread.which_stack = 0; /* resume from ksp */
/* child returns via ret_from_fork */
childregs->lkr = (unsigned long)ret_from_fork;
/* child shall return to where sys_vfork_wrapper has been called */
childregs->r5 = ra_in_syscall;
/* child gets zero as return value from syscall */
childregs->r4 = 0;
/* after task switch segment return the stack pointer shall point to the syscall frame */
childregs->sp = (unsigned long)childsyscallregs - 4;
}
return 0;
}
int copy_thread(unsigned long clone_flags,
unsigned long usp, unsigned long stk_size,
struct task_struct * p, struct pt_regs * regs)
{
unsigned long child_tos = KSTK_TOS(p);
struct pt_regs *childregs;
if (!user_mode(regs)) {
/* kernel thread */
if( usp != 0 )
panic("trying to start kernel thread with usp != 0");
/* childregs = full task switch frame on kernel stack of child */
childregs = (struct pt_regs *)(child_tos) - 1;
*childregs = *regs;
/* return via ret_from_fork */
childregs->ra = (unsigned long)ret_from_fork;
/* setup ksp/usp */
p->thread.ksp = (unsigned long)childregs - 4; /* perhaps not necessary */
childregs->sp = p->thread.ksp;
p->thread.usp = 0;
p->thread.which_stack = 0; /* kernel stack */
//printk("copy_thread1: ->pid=%d tsp=%lx r5=%lx p->thread.ksp=%lx p->thread.usp=%lx\n",
// p->pid, task_stack_page(p), childregs->r5, p->thread.ksp, p->thread.usp);
} else {
/* userspace thread (vfork, clone) */
struct pt_regs* childsyscallregs;
/* childsyscallregs = full syscall frame on kernel stack of child */
childsyscallregs = (struct pt_regs *)(child_tos) - 1; /* 32 = safety */
/* child shall have same syscall context to restore as parent has ... */
*childsyscallregs = *regs;
/* childregs = full task switch frame on kernel stack of child below * childsyscallregs */
childregs = childsyscallregs - 1;
memset(childregs, 0, sizeof(childregs));
/* user stack pointer is shared with the parent per definition of vfork */
p->thread.usp = usp;
/* kernel stack pointer is not shared with parent, it is the beginning of
* the just created new task switch segment on the kernel stack */
p->thread.ksp = (unsigned long)childregs - 4;
p->thread.which_stack = 0; /* resume from ksp */
/* child returns via ret_from_fork */
childregs->ra = (unsigned long)ret_from_fork;
/* child shall return to where sys_vfork_wrapper has been called */
childregs->r13 = (unsigned long)syscall_tail;
/* child gets zero as return value from syscall */
childregs->r11 = 0;
/* after task switch segment return the stack pointer shall point to the
* syscall frame */
childregs->sp = (unsigned long)childsyscallregs - 4;
/*printk("copy_thread2: ->pid=%d p=%lx regs=%lx childregs=%lx r5=%lx ra=%lx "
"dsf=%lx p->thread.ksp=%lx p->thread.usp=%lx\n",
p->pid, p, regs, childregs, childregs->r5, childregs->ra,
dup_syscallframe, p->thread.ksp, p->thread.usp);*/
}
return 0;
}
