如何判断给定内存地址是否对应有效的文件偏移量

First, let's recap the formula you already use to calculate the file offset from a valid virtual address:
ByteOffset = ByteVirtualAddress - (ImageBase + SectionRelativeVirtualAddress) + PointerToRawdata

To confirm if a given virtual address corresponds to a valid, editable file offset (i.e., data that actually exists in the PE file on disk, not just zero-padded virtual memory), follow these practical steps tailored to your manual hex editor workflow:

Step 1: Extract Critical PE Section Data #

First, pull these values directly from the PE file's header (you can navigate to the PE header in your hex editor, then locate the section table):

• ImageBase: The base address the PE is loaded into memory (found in the Optional Header)
• For each section in the section table:
  • SectionRVA: Relative Virtual Address of the section's start in memory
  • SectionVirtualSize: Total size of the section in memory
  • PointerToRawData: Offset of the section's data in the disk file
  • SizeOfRawData: Size of the section's data stored on disk

Step 2: Verify the Virtual Address Lives Within a Valid Section #

For each section, calculate the memory range it occupies when loaded:

• Section start in memory: ImageBase + SectionRVA
• Section end in memory: ImageBase + SectionRVA + SectionVirtualSize

If your ByteVirtualAddress does not fall within any section's memory range, it's not a valid address—it’s either unallocated memory or part of the PE header that doesn’t map to a section’s raw data.

Step 3: Calculate the Offset and Validate It Against Disk Data #

Once you’ve matched the virtual address to a section:

1. Use your formula to compute the ByteOffset
2. Check if this offset falls within the section’s raw data range on disk:
   • Raw data start: PointerToRawData
   • Raw data end: PointerToRawData + SizeOfRawData

If ByteOffset is between these two values (inclusive of the start, exclusive of the end), it’s a valid file offset you can safely edit in your hex editor. If it’s outside this range, the address corresponds to zero-padded memory that doesn’t exist in the disk file—editing it won’t affect the loaded PE.

Example Walkthrough #

Let’s use concrete values to make this tangible:

• ImageBase = 0x00400000
• Target ByteVirtualAddress = 0x00401500
• Section data: SectionRVA=0x1000, PointerToRawData=0x400, SizeOfRawData=0x2000, SectionVirtualSize=0x3000

1. Check section memory range:

   • Start: 0x400000 + 0x1000 = 0x401000
   • End: 0x401000 + 0x3000 = 0x404000
   • 0x401500 sits within this range → valid section match.

2. Calculate offset:

   • 0x401500 - (0x400000 + 0x1000) + 0x400 = 0x500 + 0x400 = 0x900

3. Validate offset against raw data:

   • Raw data end: 0x400 + 0x2000 = 0x2400
   • 0x900 is between 0x400 and 0x2400 → valid file offset

Key Tips #

• Skip sections marked as IMAGE_SCN_CNT_UNINITIALIZED_DATA (like .bss): These sections have no raw data on disk (SizeOfRawData=0), so any virtual address here won’t map to a valid file offset.
• For PE header fields (like export tables), their RVAs point to data within existing sections—follow the same steps to validate their corresponding offsets.

内容的提问来源于stack exchange，提问作者JohnSmith