I've gotten virtual memory working on ARMv8 after crafting the page tables. Oddly, _most_ of my translations are working (identity mapped) save for Flash which sits at physical address zero. I use a single function that edits the page tables, so the fact that _some_ work and _some_ do not is strange to me. Specifically I have only a few ranges mapped:Flash [0x00000000, len = 0x08000000]UART [0x09000000, len = 0x1000 ]RAM [0x40000000, len = 0x0fe00000]Secure RAM [0x4fe00000, len = 0x00200000]And again, they _all_ work except for Flash. My mapping function also works for non-identity maps. There is just something strange about that Flash range.I have an exception handler in place that I'm using to dissect the issue. I found two interesting cases when catching `Data Abort` exceptions. I encountered two Data Abort sub-types depending on the type of memory being accessed: - [1] Flash address range (e.g. 0x00000000) - ESR.ISS = 0x10 (ISS.DFSC = 0x10) - Synchronous External abort, not on translation table walk - [2] An expected unmapped address (e.g. 0x50000000) - ESR.ISS = 0x06 (ISS.DFSC = 0x06) - Synchronous External abort, on translation table walk, level 2When attempting to handle the exception for accessing an address I _do not expect_ to be in the table I get a [2] (fault at level 2 because some nearby addresses were mapped).When I attempt to handle the exception for accessing Flash which I _do expect_ to be in the table I get [1] (not in table walk). So, I am confused on what these two cases represent. What is the difference between [1] and [2]? They seem to represent the same thing. Does [1] somehow represent the case that translation failed before it tried? There are defined level 0 faults I would expect to handle if that were the case. I was expecting the "Not in table" fault for the address I was not expecting to be in the table but instead received the other.
Could it be that your mapping function handles address zero different? What if your try to start from 1MB (leaving the first 1MB of flash "unused")?
Thanks for the response. It turns out that the Flash is MMIO as Secure only. I was mapping the Flash properly but was marking it with NS. This very important bit of information was buried deep in some documentation.
With respect to the title's question I have answered it myself over at Stack Overflow if you, or anyone, wanted to take a look. I would have answered it here but it took a while before my question was even approved for submission.