no offset access after 2^32 - 3

[Atilla]

Hey,

I was testing out my gdt to make sure everything is alright. I did this after I loaded gdt and segment registers:

Code: Select all

xor dword eax,[es:0xffffffff]

But bochs triple faulted with:

read_virtual_checks(): write beyond limit

However, this works FINE:

Code: Select all

xor dword eax,[es:0xfffffffc]

0xfffffffc which is 2^32 - 3. This seems to be the maximum value of the offset I can use. Whats going on ??

[Curufir]

Hey,

I was testing out my gdt to make sure everything is alright. I did this after I loaded gdt and segment registers:

Code: Select all

xor dword eax,[es:0xffffffff]

Your trying to operate on the dword (4 bytes long) from 0xffffffff -> 100000002. Now fairly obviously the last 3 bytes of the dword are outside the 32-bit address space.