虚拟地址到物理地址的分段故障(segmentation fault in virtual address to physical address)

当我运行此代码的二进制文件时，它会抛出分段错误核心转储错误。而dmesg是：

segfault at 0 ip b7651747 sp bfb312d0 error 4 in libc-2.21.so[b75e9000+1b4000]

该代码用于将虚拟地址转换为物理地址。

#include <stdio.h> #include <string.h> #include <stdlib.h> #include <unistd.h> #include <sys/mman.h> #include <errno.h> #include <fcntl.h> #include <stdint.h> // ORIG_BUFFER will be placed in memory and will then be changed to NEW_BUFFER // They must be the same length #define ORIG_BUFFER "Hello, World!" #define NEW_BUFFER "Hello, Linux!" // The page frame shifted left by PAGE_SHIFT will give us the physcial address of the frame // Note that this number is architecture dependent. For me on x86_64 with 4096 page sizes, // it is defined as 12. If you're running something different, check the kernel source // for what it is defined as. #define PAGE_SHIFT 12 #define PAGEMAP_LENGTH 8 void* create_buffer(void); unsigned long get_page_frame_number_of_address(void *addr); int open_memory(void); void seek_memory(int fd, unsigned long offset); int main(void) { // Create a buffer with some data in it void *buffer = create_buffer(); // Get the page frame the buffer is on unsigned int page_frame_number = get_page_frame_number_of_address(buffer); printf("Page frame: 0x%x\n", page_frame_number); // Find the difference from the buffer to the page boundary unsigned int distance_from_page_boundary = (unsigned long)buffer % getpagesize(); // Determine how far to seek into memory to find the buffer uint64_t offset = (page_frame_number << PAGE_SHIFT) + distance_from_page_boundary; // Open /dev/mem, seek the calculated offset, and // map it into memory so we can manipulate it // CONFIG_STRICT_DEVMEM must be disabled for this int mem_fd = open_memory(); seek_memory(mem_fd, offset); printf("Buffer: %s\n", buffer); puts("Changing buffer through /dev/mem..."); // Change the contents of the buffer by writing into /dev/mem // Note that since the strings are the same length, there's no purpose in // copying the NUL terminator again if(write(mem_fd, NEW_BUFFER, strlen(NEW_BUFFER)) == -1) { fprintf(stderr, "Write failed: %s\n", strerror(errno)); } printf("Buffer: %s\n", buffer); // Clean up free(buffer); close(mem_fd); return 0; } void* create_buffer(void) { size_t buf_size = strlen(ORIG_BUFFER) + 1; // Allocate some memory to manipulate void *buffer = malloc(buf_size); if(buffer == NULL) { fprintf(stderr, "Failed to allocate memory for buffer\n"); exit(1); } // Lock the page in memory // Do this before writing data to the buffer so that any copy-on-write // mechanisms will give us our own page locked in memory if(mlock(buffer, buf_size) == -1) { fprintf(stderr, "Failed to lock page in memory: %s\n", strerror(errno)); exit(1); } // Add some data to the memory strncpy(buffer, ORIG_BUFFER, strlen(ORIG_BUFFER)); return buffer; } unsigned long get_page_frame_number_of_address(void *addr) { // Open the pagemap file for the current process FILE *pagemap = fopen("/proc/self/pagemap", "rb"); // Seek to the page that the buffer is on unsigned long offset = (unsigned long)addr / getpagesize() * PAGEMAP_LENGTH; if(fseek(pagemap, (unsigned long)offset, SEEK_SET) != 0) { fprintf(stderr, "Failed to seek pagemap to proper location\n"); exit(1); } // The page frame number is in bits 0-54 so read the first 7 bytes and clear the 55th bit unsigned long page_frame_number = 0; fread(&page_frame_number, 1, PAGEMAP_LENGTH-1, pagemap); page_frame_number &= 0x7FFFFFFFFFFFFF; fclose(pagemap); return page_frame_number; } int open_memory(void) { // Open the memory (must be root for this) int fd = open("/dev/mem", O_RDWR); if(fd == -1) { fprintf(stderr, "Error opening /dev/mem: %s\n", strerror(errno)); exit(1); } return fd; } void seek_memory(int fd, unsigned long offset) { unsigned pos = lseek(fd, offset, SEEK_SET); if(pos == -1) { fprintf(stderr, "Failed to seek /dev/mem: %s\n", strerror(errno)); exit(1); } }

When i run the binary file of this code it throws an segmentation fault core dumped error. And the dmesg is: