Re: [PATCH] i386 - sys_clone from vsyscall

[Daniel fernandez <ergot86@gmail.com>]

Thanks for your work on the patch

> Your patch almost works but it copies the stack into the parent's address space.
> Using access_process_vm() fixes it.  However, that still leaves unfixed the case
> where vsyscall-int80 is used.

I copy the stack into the parent's address space becuase in this case
the memory is shared, but  access_process_vm() is more elegant :).
About vsyscall-int80, I don't know how to test that case in my
computer but I think a solution could be:

add a INT80H_RETURN symbol:

 .LSTART_vsyscall:
          int $0x80
 .globl INT80H_RETURN
 INT80H_RETURN:
          ret
  .LEND_vsyscall:

and then in process.c:

  int size = 0 ;
  childregs->eax = 0;

    if ((void *)regs->eip == SYSENTER_RETURN)
                size = sizeof(vsyscall_stack) ;
    if ((void *)regs->eip == INT80H_RETURN)
                size = sizeof(unsigned long) ;

       if (regs->esp != esp && size) {
               if (copy_from_user(vsyscall_stack, (void *)regs->esp, size))
                       return -EFAULT;
               if (access_process_vm(p, esp - size, vsyscall_stack,
size, 1) != size)
                       return -EFAULT;
               esp -= size;
       }
       childregs->esp = esp;

I hope somebody can test if it works that way.
Regards