/*
* Borrowed from Gist: https://gist.github.com/pleiadesian/41f00ebc41dbe91417866d466ecc62b7
*/
#define _XOPEN_SOURCE 700
#include <fcntl.h> /* open */
#include <stdint.h> /* uint64_t  */
#include <stdio.h> /* printf */
#include <stdlib.h> /* size_t */
#include <unistd.h> /* pread, sysconf */
#include "virt_to_phy.h"


/* Parse the pagemap entry for the given virtual address.
 *
 * @param[out] entry      the parsed entry
 * @param[in]  pagemap_fd file descriptor to an open /proc/pid/pagemap file
 * @param[in]  vaddr      virtual address to get entry for
 * @return 0 for success, 1 for failure
 */
int  pagemap_get_entry(PagemapEntry *entry, int pagemap_fd, uintptr_t vaddr)
{
	size_t nread;
	ssize_t ret;
	uint64_t data;
	uintptr_t vpn;

	vpn = vaddr / sysconf(_SC_PAGE_SIZE);
	nread = 0;
	while (nread < sizeof(data)) {
		ret = pread(pagemap_fd, ((uint8_t*)&data) + nread, sizeof(data) - nread,
			vpn * sizeof(data) + nread);
		nread += ret;
		if (ret <= 0) {
			return 1;
		}
	}
	entry->pfn = data & (((uint64_t)1 << 55) - 1);
	entry->soft_dirty = (data >> 55) & 1;
	entry->file_page = (data >> 61) & 1;
	entry->swapped = (data >> 62) & 1;
	entry->present = (data >> 63) & 1;
	return 0;
}

/* Convert the given virtual address to physical using /proc/PID/pagemap.
 *
 * @param[out] paddr physical address
 * @param[in]  pid   process to convert for
 * @param[in] vaddr virtual address to get entry for
 * @return 0 for success, 1 for failure
 */
int virt_to_phys_user(uintptr_t *paddr, uintptr_t vaddr)
{
	char pagemap_file[BUFSIZ];
	int pagemap_fd;

	snprintf(pagemap_file, sizeof(pagemap_file), "/proc/self/pagemap");
	pagemap_fd = open(pagemap_file, O_RDONLY);
	if (pagemap_fd < 0) {
		return 1;
	}
	PagemapEntry entry;
	if (pagemap_get_entry(&entry, pagemap_fd, vaddr)) {
		return 1;
	}
	close(pagemap_fd);
	*paddr = (entry.pfn * sysconf(_SC_PAGE_SIZE)) + (vaddr % sysconf(_SC_PAGE_SIZE));
	return 0;
}

