这个函数是跟体系结构相关的。
asmlinkage void ret_from_fork(void) asm("ret_from_fork");
int copy_thread(unsigned long clone_flags, unsigned long stack_start,
unsigned long stk_sz, struct task_struct *p)
{
struct pt_regs *childregs = task_pt_regs(p);
memset(&p->thread.cpu_context, 0, sizeof(struct cpu_context));
if (likely(!(p->flags & PF_KTHREAD))) {
*childregs = *current_pt_regs();
childregs->regs[0] = 0;
/*
* Read the current TLS pointer from tpidr_el0 as it may be
* out-of-sync with the saved value.
*/
*task_user_tls(p) = read_sysreg(tpidr_el0);
if (stack_start) {
if (is_compat_thread(task_thread_info(p)))
childregs->compat_sp = stack_start;
else
childregs->sp = stack_start;
}
/*
* If a TLS pointer was passed to clone (4th argument), use it
* for the new thread.
*/
if (clone_flags & CLONE_SETTLS)
p->thread.tp_value = childregs->regs[3];
} else {
memset(childregs, 0, sizeof(struct pt_regs));
childregs->pstate = PSR_MODE_EL1h;
if (IS_ENABLED(CONFIG_ARM64_UAO) &&
cpus_have_cap(ARM64_HAS_UAO))
childregs->pstate |= PSR_UAO_BIT;
p->thread.cpu_context.x19 = stack_start;
p->thread.cpu_context.x20 = stk_sz;
}
p->thread.cpu_context.pc = (unsigned long)ret_from_fork;
p->thread.cpu_context.sp = (unsigned long)childregs;
ptrace_hw_copy_thread(p);
return 0;
}
