77 lines
2.3 KiB
C
77 lines
2.3 KiB
C
// XXX: Taken from https://stackoverflow.com/a/45128487
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#define _XOPEN_SOURCE 700
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#include <fcntl.h> /* open */
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#include <stdint.h> /* uint64_t */
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#include <stdio.h> /* printf */
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#include <stdlib.h> /* size_t */
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#include <unistd.h> /* pread, sysconf */
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typedef struct {
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uint64_t pfn : 55;
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unsigned int soft_dirty : 1;
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unsigned int file_page : 1;
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unsigned int swapped : 1;
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unsigned int present : 1;
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} PagemapEntry;
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/* Parse the pagemap entry for the given virtual address.
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*
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* @param[out] entry the parsed entry
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* @param[in] pagemap_fd file descriptor to an open /proc/pid/pagemap file
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* @param[in] vaddr virtual address to get entry for
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* @return 0 for success, 1 for failure
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*/
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int pagemap_get_entry(PagemapEntry *entry, int pagemap_fd, uintptr_t vaddr)
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{
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size_t nread;
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ssize_t ret;
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uint64_t data;
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uintptr_t vpn;
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vpn = vaddr / sysconf(_SC_PAGE_SIZE);
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nread = 0;
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while (nread < sizeof(data)) {
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ret = pread(pagemap_fd, ((uint8_t*)&data) + nread, sizeof(data) - nread,
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vpn * sizeof(data) + nread);
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nread += ret;
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if (ret <= 0) {
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return 1;
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}
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}
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entry->pfn = data & (((uint64_t)1 << 55) - 1);
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entry->soft_dirty = (data >> 55) & 1;
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entry->file_page = (data >> 61) & 1;
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entry->swapped = (data >> 62) & 1;
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entry->present = (data >> 63) & 1;
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return 0;
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}
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/* Convert the given virtual address to physical using /proc/PID/pagemap.
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*
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* @param[name] name of variable
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* @param[in] vaddr virtual address to get entry for
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* @return paddr (physical address) on success, exit on failure
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*/
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int virt_to_phys_user(char* name, uintptr_t vaddr)
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{
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char pagemap_file[BUFSIZ];
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int pagemap_fd;
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snprintf(pagemap_file, sizeof(pagemap_file), "/proc/%ju/pagemap", (uintmax_t)getpid());
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pagemap_fd = open(pagemap_file, O_RDONLY);
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if (pagemap_fd < 0) {
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printf("Failed to open pagemap for process!");
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exit(-1);
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}
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PagemapEntry entry;
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if (pagemap_get_entry(&entry, pagemap_fd, vaddr)) {
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printf("Failed to get entry for pagemap!");
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exit(-1);
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}
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close(pagemap_fd);
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uintptr_t paddr = (entry.pfn * sysconf(_SC_PAGE_SIZE)) + (vaddr % sysconf(_SC_PAGE_SIZE));
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printf("%s: virt @ %p, phys @ %p\n", name, (void *)vaddr, (void*)paddr);
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return paddr;
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}
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