Add support for shareable pages and additional access privileges
Detail:
This set of changes:
* Refactors page table entry encoding/decoding so that it's (mostly) performed via functions in the MMU files (s.ARM600, s.VMSAv6) rather than on an ad-hoc basis as was the case previously
* Page table entry encoding/decoding performed during ROM init is also handled via the MMU functions, which resolves some cases where the wrong cache policy was in use on ARMv6+
* Adds basic support for shareable pages - on non-uniprocessor systems all pages will be marked as shareable (however, we are currently lacking ARMops which broadcast cache maintenance operations to other cores, so safe sharing of cacheable regions isn't possible yet)
* Adds support for the VMSA XN flag and the "privileged ROM" access permission. These are exposed via RISC OS access privileges 4 and above, taking advantage of the fact that 4 bits have always been reserved for AP values but only 4 values were defined
* Adds OS_Memory 17 and 18 to convert RWX-style access flags to and from RISC OS access privelege numbers; this allows us to make arbitrary changes to the mappings of AP values 4+ between different OS/hardware versions, and allows software to more easily cope with cases where the most precise AP isn't available (e.g. no XN on <=ARMv5)
* Extends OS_Memory 24 (CheckMemoryAccess) to return executability information
* Adds exported OSMem header containing definitions for OS_Memory and OS_DynamicArea
File changes:
- Makefile - export C and assembler versions of hdr/OSMem
- Resources/UK/Messages - Add more text for OS_Memory errors
- hdr/KernelWS - Correct comment regarding DCacheCleanAddress. Allocate workspace for MMU_PPLTrans and MMU_PPLAccess.
- hdr/OSMem - New file containing exported OS_Memory and OS_DynamicArea constants, and public page flags
- hdr/Options - Reduce scope of ARM6support to only cover builds which require ARMv3 support
- s/AMBControl/Workspace - Clarify AMBNode_PPL usage
- s/AMBControl/growp, mapslot, mapsome, memmap - Use AreaFlags_ instead of AP_
- s/AMBControl/main, memmap - Use GetPTE instead of generating page table entry manually
- s/ARM600 - Remove old coments relating to lack of stack. Update BangCam to use GetPTE. Update PPL tables, removing PPLTransL1 (L1 entries are now derived from L2 table on demand) and adding a separate table for ARM6. Implement the ARM600 versions of the Get*PTE ('get page table entry') and Decode*Entry functions
- s/ARMops - Add Init_PCBTrans function to allow relevant MMU_PPLTrans/MMU_PCBTrans pointers to be set up during the pre-MMU stage of ROM init. Update ARM_Analyse to set up the pointers that are used post MMU init.
- s/ChangeDyn - Move a bunch of flags to hdr/OSMem. Rename the AP_ dynamic area flags to AreaFlags_ to avoid name clashes and confusion with the page table AP_ values exported by Hdr:MEMM.ARM600/Hdr:MEMM.VMSAv6. Also generate the relevant flags for OS_Memory 24 so that it can refer to the fixed areas by their name instead of hardcoding the permissions.
- s/GetAll - GET Hdr:OSMem
- s/HAL - Change initial page table setup to use DA/page flags and GetPTE instead of building page table entries manually. Simplify AllocateL2PT by removing the requirement for the user to supply the access perimssions that will be used for the area; instead for ARM6 we just assume that cacheable memory is the norm and set L1_U for any L1 entry we create here.
- s/Kernel - Add GetPTE macro (for easier integration of Get*PTE functions) and GenPPLAccess macro (for easy generation of OS_Memory 24 flags)
- s/MemInfo - Fixup OS_Memory 0 to not fail on seeing non-executable pages. Implement OS_Memory 17 & 18. Tidy up some error generation. Make OS_Memory 13 use GetPTE. Extend OS_Memory 24 to return (non-) executability information, to use the named CMA_ constants generated by s/ChangeDyn, and to use the Decode*Entry functions when it's necessary to decode page table entries.
- s/NewReset - Use AreaFlags_ instead of AP_
- s/VMSAv6 - Remove old comments relating to lack of stack. Update BangCam to use GetPTE. Update PPL tables, removing PPLTransL1 (L1 entries are now derived from L2 table on demand) and adding a separate table for shareable pages. Implement the VMSAv6 versions of the Get*PTE and Decode*Entry functions.
Admin:
Tested on Raspberry Pi 1, Raspberry Pi 3, Iyonix, RPCEmu (ARM6 & ARM7), comparing before and after CAM and page table dumps to check for any unexpected differences
Version 5.55. Tagged as 'Kernel-5_55'
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hdr/OSMem
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