virt_to_phys_user.cpp

#include <fcntl.h> /* open */
#include <stdint.h> /* uint64_t  */
#include <stdio.h> /* printf */
#include <stdlib.h> /* size_t */
#include <unistd.h> /* pread, sysconf */

typedef struct {
	    uint64_t pfn : 55;
	        unsigned int soft_dirty : 1;
		    unsigned int file_page : 1;
		        unsigned int swapped : 1;
			    unsigned int present : 1;
} PagemapEntry;

/* 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, char* fname, uintptr_t vaddr)
{
	int pagemap_fd = open(fname, O_RDONLY);
	if (pagemap_fd < 0) {
		printf("COULDNT OPEN FILE %s", fname);
		        return 1;
	}
	PagemapEntry entry;
	if (pagemap_get_entry(&entry, pagemap_fd, vaddr)) {
		printf("ERROR READING Pagemap File!!!");
		return 1;
        }
	close(pagemap_fd );
	printf("_SC_PAGE_SIZE: %i", _SC_PAGE_SIZE);
	*paddr = (entry.pfn * sysconf(_SC_PAGE_SIZE)) + (vaddr % sysconf(_SC_PAGE_SIZE));
	return 0;
}

// Inputs: 1. filename containing pagemap, 2. Virt addr to be converted, in hex
int main(int argc, char **argv)
{
	uintptr_t vaddr, paddr = 0;
	char* pagemap_fname = argv[1];
	 vaddr = strtoull(argv[2], NULL, 0);
	if (virt_to_phys_user(&paddr, pagemap_fname , vaddr))
	{
		printf("ERROR converting VA->PA!!! \n");
		return EXIT_FAILURE;
	}
	printf("\n FOUND VA->PA: va: %li, PA: 0x%jx \n", vaddr, paddr);
}