99 lines
3.9 KiB
C
99 lines
3.9 KiB
C
/*
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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StarForth — Steady-State Virtual Machine Runtime
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Copyright (c) 2023–2025 Robert A. James
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All rights reserved.
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This file is part of the StarForth project.
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Licensed under the StarForth License, Version 1.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at:
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https://github.com/star.4th@proton.me/StarForth/LICENSE.txt
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This software is provided "AS IS", WITHOUT WARRANTY OF ANY KIND,
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express or implied, including but not limited to the warranties of
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merchantability, fitness for a particular purpose, and noninfringement.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/**
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* reloc_stub.c - Provide a minimal .reloc section for PE/COFF EFI loader
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*
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* Some firmware refuses to load images without a Base Relocation Directory.
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* This stub supplies an empty relocation block to satisfy the loader.
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*/
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#include <stdint.h>
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/**
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* @brief PE/COFF Base Relocation Block header.
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*
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* Mirrors the @c IMAGE_BASE_RELOCATION layout from the PE specification:
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* - @c page_rva — RVA of the 4 KB page that the following entries apply to.
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* - @c block_size — total byte size of this block including the header and
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* all entries (minimum 8 bytes for the header alone).
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* - @c entry — one or more 16-bit relocation entries packed as
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* TYPE (4 bits) | OFFSET (12 bits); TYPE=0 / OFFSET=0
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* is a no-op padding entry used to 32-bit-align the block.
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*
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* Marked @c packed to suppress any padding the compiler might insert between
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* fields; @c aligned(4) ensures the block sits on a 4-byte boundary as
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* required by the PE loader.
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*/
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struct reloc_block {
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uint32_t page_rva;
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uint32_t block_size;
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uint16_t entry; /* TYPE=0, OFFSET=0 */
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} __attribute__((packed, aligned(4)));
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/**
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* @brief Minimal @c .reloc section stub to satisfy UEFI firmware loaders.
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*
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* Some UEFI implementations (notably certain hardware vendor firmware and
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* strict OVMF builds) refuse to load a PE32+ image that lacks a Base
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* Relocation Directory entry in the optional-header Data Directory. Even
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* for monolithic position-independent images that require no run-time fix-ups,
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* the presence of the @c .reloc section with a well-formed (but empty)
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* relocation block is required to pass the firmware's image validation.
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*
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* This single statically-allocated @c reloc_block satisfies the requirement:
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* - @c page_rva = 0 — applies to the first 4 KB page (convention for stubs).
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* - @c block_size = sizeof(reloc_block) — minimal well-formed block (8 bytes
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* + 2 bytes for the single no-op entry = 10 bytes).
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* - @c entry = 0 — TYPE=0 (absolute, no-op) / OFFSET=0; ignored by the loader.
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*
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* The @c used attribute prevents the compiler/linker from discarding the
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* symbol as unreferenced; the @c section(".reloc") attribute places it
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* in the named PE section so the linker emits the correct Data Directory.
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*/
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__attribute__((section(".reloc"), used))
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static const struct reloc_block reloc_stub = {
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.page_rva = 0,
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.block_size = sizeof(struct reloc_block),
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.entry = 0
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};
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