c - sparc_do_fork() 究竟做了什么？

Question

我试图找出这个函数的功能，但我找不到。它在 Linux/arch/sparc/kernel/process_32.c 中定义，谢谢

asmlinkage int sparc_do_fork(unsigned long clone_flags,
                             unsigned long stack_start,
                             struct pt_regs *regs,
                             unsigned long stack_size)
{
    unsigned long parent_tid_ptr, child_tid_ptr;
    unsigned long orig_i1 = regs->u_regs[UREG_I1];
    long ret;

    parent_tid_ptr = regs->u_regs[UREG_I2];
    child_tid_ptr = regs->u_regs[UREG_I4];

    ret = do_fork(clone_flags, stack_start, stack_size,
        (int __user *) parent_tid_ptr,
        (int __user *) child_tid_ptr);

    /* If we get an error and potentially restart the system
     * call, we're screwed because copy_thread() clobbered
     * the parent's %o1.  So detect that case and restore it
     * here.
     */
    if ((unsigned long)ret >= -ERESTART_RESTARTBLOCK)
        regs->u_regs[UREG_I1] = orig_i1;

    return ret;
}

Answer 1

它似乎就在源代码中。

它是常规 Linux do_fork() 调用的包装器，用于保存和恢复数据(具体来说，regs->u_regs[UREG_I1]，等同于SPARC 输出寄存器 1)，否则在某些情况下会损坏:

/* If we get an error and potentially restart the system
     * call, we're screwed because copy_thread() clobbered
     * the parent's %o1.  So detect that case and restore it
     * here.
     */

它用:

unsigned long orig_i1 = regs->u_regs[UREG_I1];      // Save it.

ret = do_fork(...);

if ((unsigned long)ret >= -ERESTART_RESTARTBLOCK)   // It may be corrupt
    regs->u_regs[UREG_I1] = orig_i1;                //   so restore it.