How to allocate 500MB+ physically contiguous memory in a Linux kernel module and copy data to that memory from a userspace process?

Question

I tried using kmalloc() but it's not providing more than 4MB. Also, can I use ioctl to transfer that large data from a user process to a kernel module? Is there any limitations for the buffer size?

I also read some documentation about __get_free_page() and dma_alloc_coherent() but these functions also do not provide that much memory.