play-with-physical-addresses-in-linux

= Play with physical addresses in Linux

Convert virtual addresses to physical from user space with `/proc/<pid>/pagemap` and from kernel space with `virt_to_phys`:
* https://stackoverflow.com/questions/5748492/is-there-any-api-for-determining-the-physical-address-from-virtual-address-in-li/45128487#45128487
* https://github.com/cirosantilli/linux-kernel-module-cheat/blob/1f4f7faebacca75267cc1d63bfeffc30080d017d/kernel_module/user/virt_to_phys_user.c
* `virt_to_phys`:
  * https://github.com/cirosantilli/linux-kernel-module-cheat/blob/0677dbd4b582d1a913462d75caad0abf21e87f32/kernel_module/virt_to_phys.c
  * https://github.com/cirosantilli/linux-kernel-module-cheat/blob/1f4f7faebacca75267cc1d63bfeffc30080d017d/kernel_module/user/virt_to_phys_user.c

Dump all page tables from userspace with `/proc/<pid>/maps` and `/proc/<pid>/pagemap`:
* https://github.com/cirosantilli/linux-kernel-module-cheat/blob/1f4f7faebacca75267cc1d63bfeffc30080d017d/kernel_module/user/virt_to_phys_user.c
* https://stackoverflow.com/questions/6284810/proc-pid-pagemaps-and-proc-pid-maps-linux/45500208#45500208

Read and write physical addresses from userspace with `/dev/mem`:
* https://stackoverflow.com/questions/12040303/accessing-physical-address-from-user-space/45127890#45127890
* https://free-electrons.com/pub/mirror/devmem2.c
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