作为一个编程练习，我正在用 C 编写一个标记和清除垃圾收集器。我希望扫描数据段（全局等）以查找指向已分配内存的指针，但我不知道如何获取该段的地址。我怎么能这样做？
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33
如果你在 Windows 上工作，那么有一些 Windows API 可以帮助你。
//store the base address the loaded Module
dllImageBase = (char*)hModule; //suppose hModule is the handle to the loaded Module (.exe or .dll)
//get the address of NT Header
IMAGE_NT_HEADERS *pNtHdr = ImageNtHeader(hModule);
//after Nt headers comes the table of section, so get the addess of section table
IMAGE_SECTION_HEADER *pSectionHdr = (IMAGE_SECTION_HEADER *) (pNtHdr + 1);
ImageSectionInfo *pSectionInfo = NULL;
//iterate through the list of all sections, and check the section name in the if conditon. etc
for ( int i = 0 ; i < pNtHdr->FileHeader.NumberOfSections ; i++ )
{
char *name = (char*) pSectionHdr->Name;
if ( memcmp(name, ".data", 5) == 0 )
{
pSectionInfo = new ImageSectionInfo(".data");
pSectionInfo->SectionAddress = dllImageBase + pSectionHdr->VirtualAddress;
**//range of the data segment - something you're looking for**
pSectionInfo->SectionSize = pSectionHdr->Misc.VirtualSize;
break;
}
pSectionHdr++;
}
将 ImageSectionInfo 定义为，
struct ImageSectionInfo
{
char SectionName[IMAGE_SIZEOF_SHORT_NAME];//the macro is defined WinNT.h
char *SectionAddress;
int SectionSize;
ImageSectionInfo(const char* name)
{
strcpy(SectioName, name);
}
};
这是一个完整的、最小的 WIN32 控制台程序，您可以在 Visual Studio 中运行，它演示了 Windows API 的使用：
#include <stdio.h>
#include <Windows.h>
#include <DbgHelp.h>
#pragma comment( lib, "dbghelp.lib" )
void print_PE_section_info(HANDLE hModule) // hModule is the handle to a loaded Module (.exe or .dll)
{
// get the location of the module's IMAGE_NT_HEADERS structure
IMAGE_NT_HEADERS *pNtHdr = ImageNtHeader(hModule);
// section table immediately follows the IMAGE_NT_HEADERS
IMAGE_SECTION_HEADER *pSectionHdr = (IMAGE_SECTION_HEADER *)(pNtHdr + 1);
const char* imageBase = (const char*)hModule;
char scnName[sizeof(pSectionHdr->Name) + 1];
scnName[sizeof(scnName) - 1] = '\0'; // enforce nul-termination for scn names that are the whole length of pSectionHdr->Name[]
for (int scn = 0; scn < pNtHdr->FileHeader.NumberOfSections; ++scn)
{
// Note: pSectionHdr->Name[] is 8 bytes long. If the scn name is 8 bytes long, ->Name[] will
// not be nul-terminated. For this reason, copy it to a local buffer that's nul-terminated
// to be sure we only print the real scn name, and no extra garbage beyond it.
strncpy(scnName, (const char*)pSectionHdr->Name, sizeof(pSectionHdr->Name));
printf(" Section %3d: %p...%p %-10s (%u bytes)\n",
scn,
imageBase + pSectionHdr->VirtualAddress,
imageBase + pSectionHdr->VirtualAddress + pSectionHdr->Misc.VirtualSize - 1,
scnName,
pSectionHdr->Misc.VirtualSize);
++pSectionHdr;
}
}
// For demo purpopses, create an extra constant data section whose name is exactly 8 bytes long (the max)
#pragma const_seg(".t_const") // begin allocating const data in a new section whose name is 8 bytes long (the max)
const char const_string1[] = "This string is allocated in a special const data segment named \".t_const\".";
#pragma const_seg() // resume allocating const data in the normal .rdata section
int main(int argc, const char* argv[])
{
print_PE_section_info(GetModuleHandle(NULL)); // print section info for "this process's .exe file" (NULL)
}
如果您对 DbgHelp 库的其他用途感兴趣，此页面可能会有所帮助。
您可以在此处阅读 PE 图像格式，以了解详细信息。一旦你理解了 PE 格式，你就可以使用上面的代码，甚至可以修改它以满足你的需要。
- 体育格式
- Windows API 和结构
我认为这将在很大程度上帮助您，其余的您可以自己研究:-)
顺便说一句，您还可以看到这个线程，因为所有这些都与此相关：
于 2010-11-30T17:50:48.827 回答
21
linux（和其他unix）的文本（程序代码）和数据的界限：
#include <stdio.h>
#include <stdlib.h>
/* these are in no header file, and on some
systems they have a _ prepended
These symbols have to be typed to keep the compiler happy
Also check out brk() and sbrk() for information
about heap */
extern char etext, edata, end;
int
main(int argc, char **argv)
{
printf("First address beyond:\n");
printf(" program text segment(etext) %10p\n", &etext);
printf(" initialized data segment(edata) %10p\n", &edata);
printf(" uninitialized data segment (end) %10p\n", &end);
return EXIT_SUCCESS;
}
于 2010-11-30T00:56:19.547 回答
1
由于您可能必须使垃圾收集器成为程序运行的环境，因此您可以直接从 elf 文件中获取它。
于 2010-11-29T23:10:37.217 回答
0
加载可执行文件来自的文件并解析 PE 标头，用于 Win32。我不知道在其他操作系统上。请记住，如果您的程序包含多个文件（例如 DLL），您可能有多个数据段。
于 2010-11-29T23:09:40.810 回答
0
对于 iOS，您可以使用此解决方案。它显示了如何查找文本段范围，但您可以轻松更改它以找到您喜欢的任何段。
于 2014-08-24T11:20:23.833 回答