Flat Virtual Address Space under Windows CE

On 6/10/05, song titan wrote:

I often read in books about “flat virtual address space.” Combined with what we discussed last time about private data protection within processes in WinCE — I just thought about it, can I understand it this way?

Because embedded storage media includes many types: RAM, ROM, FLASH, etc., the MMU maps all of these to a flat virtual address space. This way, non-contiguous memory can be made contiguous through page tables. Hence the name “flat.”

Also, last time you mentioned that if “Enable kernel debug” is selected, there’s no slot boundary, and process private data can’t be protected. I recall that in desktop Windows, the MMU controls this read/write permission — so here, is this permission mechanism just disabled?

I think “flat” means all processes share a single address space. After enabling Full Kernel Mode, the boundaries between slots are removed — it’s as if all 32 processes are actually one process. However, MMU protection still exists. For example, if a memory region is read-only in process A, then all processes can read it. But if any process tries to write to that memory, it will cause an access violation.