c – 如何确定哪个动态库负责创建指针？

假设您有一个使用dlopen()加载多个共享对象/动态库的程序.给定指向全局对象的指针(例如静态成员变量),是否可以确定指针是在哪个库的边界中分配的？

解决方法:

您可以使用文件/ proc / self / maps解析流程图,并查看指针地址的界限,全局变量将位于.data或.bss段中.

示例库lib.c：

static int object;

int *
dummy(void)
{
  return &object;
}

test.c,为简单起见,未处理错误：

#include <stdio.h>
#include <dlfcn.h>
#include <unistd.h>
#include <inttypes.h>
#include <assert.h>
#include <linux/limits.h>

static void which_library(void *p);

int
main(int argc, char **argv)
{
  void *handle;
  void *object;

  handle = dlopen("./lib.so", RTLD_NOW);
  assert(handle);

  object = ((int *(*)(void)) dlsym(handle, "dummy"))();
  which_library(object);
  dlclose(handle);

  return 0;
}

static void
which_library(void *p)
{
  FILE *maps;
  char buffer[49+PATH_MAX+1];

  maps = fopen("/proc/self/maps", "r");
  assert(maps);

  while(fgets(buffer, sizeof(buffer) - 1, maps)) {
    char path[PATH_MAX+1];
    uintptr_t starts;
    uintptr_t ends;

    sscanf(buffer, "%" PRIxPTR "-%" PRIxPTR " %*s %*x %*x:%*x %*d %s", &starts, &ends, path);
    if((uintptr_t)p >= starts && (uintptr_t)p < ends) {
      printf("%p => %s\n", p, path);
      break;
    }
  }

  fclose(maps);
}

测试：

$gcc -Wall -shared lib.c -o lib.so 
$gcc -Wall test.c -ldl
$./a.out 
0xb779f5f8 => /home/barakat/Desktop/lib.so
$

标签：c-2,c-3,linux,dynamic-library,shared-objects
来源： https://codeday.me/bug/20190609/1206880.html