Linux 将虚拟内存范围映射到现有虚拟内存范围？

发布于 2024-10-07 02:31:29 字数 339 浏览 3 评论 0原文

在Linux中，有没有一种方法（在用户空间中）将虚拟地址范围映射到支持现有虚拟地址范围的物理页面？ mmap() 函数只允许映射文件或“新”物理页。我需要能够做这样的事情：

int* addr1 = malloc(SIZE);
int* addr2 = 0x60000;      // Assume nothing is allocated here
fancy_map_function(addr1, addr2, SIZE);
assert(*addr1 == *addr2);  // Should succeed
assert(addr1 != addr2);    // Should succeed

原文

In Linux, is there a way (in user space) to map a virtual address range to the physical pages that back an existing virtual address range? The mmap() function only allows one to map files or "new" physical pages. I need to be able to do something like this:

int* addr1 = malloc(SIZE);
int* addr2 = 0x60000;      // Assume nothing is allocated here
fancy_map_function(addr1, addr2, SIZE);
assert(*addr1 == *addr2);  // Should succeed
assert(addr1 != addr2);    // Should succeed

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沉鱼一梦 2024-10-14 02:31:29

我很好奇，所以我测试了问题评论中建议的共享内存想法，它似乎有效：（

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <assert.h>

#define SIZE 256
int main (int argc, char ** argv) {
  int fd;
  int *addr1, *addr2;

  fd = shm_open("/example_shm", O_RDWR | O_CREAT, 0777);
  ftruncate( fd, SIZE);
  addr1 = mmap(0, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  addr2 = mmap(0, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

  printf("addr1 = %p addr2 = %p\n", addr1, addr2);
  *addr1 = 0x12345678;
  assert(*addr1 == *addr2);  // Should succeed
  assert(addr1 != addr2);    // Should succeed

  return 0;
}

显然真实的代码会想要检查系统调用的返回值是否有错误并自行清理）

I was curious so I tested the shared memory idea suggested in question comments, and it seems to work:

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/mman.h>
#include <assert.h>

#define SIZE 256
int main (int argc, char ** argv) {
  int fd;
  int *addr1, *addr2;

  fd = shm_open("/example_shm", O_RDWR | O_CREAT, 0777);
  ftruncate( fd, SIZE);
  addr1 = mmap(0, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
  addr2 = mmap(0, SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);

  printf("addr1 = %p addr2 = %p\n", addr1, addr2);
  *addr1 = 0x12345678;
  assert(*addr1 == *addr2);  // Should succeed
  assert(addr1 != addr2);    // Should succeed

  return 0;
}

(Obviously real code will want to check the return value of the syscalls for errors and clean up after itself)

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