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Subjectcopy_*_user
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I am investigating copy_from_user  and copy_to_user in linux under
i386. These two function both take a pointer with virtual address and
a pointer with physical address.

copy_from_user calls __copy_from_user_ll and copy_to_user calls
__copy_to_user_ll. It make sense to me that __copy_to_user_ll converts
the virtual address to physical address using the current process's
page table.


unsigned long __copy_to_user_ll(void __user *to, const void *from,
unsigned long n)
{
...
retval = get_user_pages(current, current->mm,
(unsigned long)to, 1, 1, 0, &pg, NULL);
if (retval == -ENOMEM && is_global_init(current)) {
up_read(&current->mm->mmap_sem);
congestion_wait(BLK_RW_ASYNC, HZ/50);
goto survive;
}
if (retval != 1) {
up_read(&current->mm->mmap_sem);
break;
}
maddr = kmap_atomic(pg, KM_USER0);
memcpy(maddr + offset, from, len);
...
}
But it seems to be that __copy_from_user_ll is not converted the
address at all before attempting to copy. Can someone help explain to
me why ?


Thanks


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