Negative 64-bit addresses fail to be disassembled properly

[10110111]

In 64-bit mode at address of 0xffffffffff600000 usually resides [vsyscall], which contains the following code

48 c7 c0 60 00 00 00   mov rax,0x60
0f 05                  syscall
c3                     ret
cc cc cc ...           times 4086 int3

But EDB disassembles the first two instructions as 9 single-byte invalid instructions. Apparently it fails to read the bulk of memory, but succeeds in reading single bytes...

[10110111]

If you try to double-click this entry in Memory Regions dialog, the data view will show empty contents, apparently also failing to read it in blocks.

I'll look into fixing this.