RISC-V FDPIC/NOMMU toolchain/runtime support

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" summary

Proposes an FDPIC psABI for RISC‑V that reserves an ABI GP register per module so read‑only text can be shared on NOMMU systems while data maps independently; introduces a function descriptor table (FDT) holding (PC, GP) pairs for every external function, forces PLT/PLT‑slot changes (16‑byte slots) and extra prologue stack save/restore of GP, and uses 12‑bit GP‑offset relaxations. Requires GCC/gas/ld changes, dynamic loader updates (glibc/musl) and a small kernel patch; design is early stage, not yet fully implemented.

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" chapters (16)

1. 0:00Intro
2. 0:16Western Digital
3. 2:19Overview
4. 3:44Design Goals and Non-Goals
5. 5:53MMU PIC Shared Program Mapping
6. 8:00NOMMU PIC (Flat) Unshared Program Mapping
7. 9:11NOMMU FDPIC Shared Program Mapping
8. 9:54Text To Data Addressing
9. 11:02GP-Relative Addressing
10. 13:43Local Data Addressing
11. 14:40External (Preemptible) Data Addressing Using the Global Offset Table (GOT)
12. 17:29Procedure Calls
13. 21:25FDT Structure Dynamic relocation required
14. 24:15Taking A Function's Address
15. 25:22Lazy Binding
16. 25:33Implementation Goals

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