Robert Allan JamesandClaude Sonnet 5
2c45744995
Real, complete verification logic -- not yet wired to any write path. homeblocks_sig_check(dev, sig_start_fblock, out_sig) reads the 4 consecutive 1KB blkio forth-blocks the 4KB header spans, verifies magic -> version -> CRC-64 in order, returns HOMEBLOCKS_SIG_OK/_BLANK/ _BAD_VERSION/_BAD_CRC/_READ_ERROR. Reuses block_subsystem.c's existing CRC-64/ISO (compute_crc64, previously static/file-local, now exposed via block_subsystem.h) rather than a second CRC implementation -- same algorithm already proven via per-block checksums. Takes the header's starting block as a plain parameter rather than resolving it internally: verifies a signature given a location, finding that location (GPT-partition-relative) stays the caller's job. Verified against the actual shipped code, not a reimplementation: a standalone host test links the real homeblocks_sig.c against a fake in-memory blkio_dev and exercises all four outcomes -- blank media, a correctly-minted header (round-trips drive_uuid/minted_time_ns), a flipped CRC, an unrecognized version. All four pass. A full QEMU-hotplug live test isn't proportionate yet since nothing calls this function from the live kernel path -- wiring it into the attach path is the next punch-list item. Clean zero-warning compile and clean boot on all three architectures confirms no build/link regression from exposing compute_crc64 and adding the new source file to every kernel build. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01CXjAPTEKrgY2Mrk25KoLDn
88 lines
3.1 KiB
C
88 lines
3.1 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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*/
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/**
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* homeblocks_sig.c - Drive signature check (FABRIC-3.md, Milestone 4).
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* See starkernel/homeblocks_sig.h for the format and interface design.
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*/
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#include "starkernel/homeblocks_sig.h"
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#include <stddef.h>
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#include <string.h>
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#include "blkio.h"
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#include "block_subsystem.h" /* compute_crc64() -- same CRC-64/ISO this file's
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* check reuses rather than duplicating */
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uint64_t homeblocks_sig_compute_crc(const homeblocks_sig_t *sig) {
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/* Covers every field up to but not including hdr_crc itself (and never
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* _pad, which sits after it) -- offsetof is the exact boundary, not a
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* hand-counted byte offset that could drift out of sync with the
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* struct's own field list. */
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size_t crc_span = offsetof(homeblocks_sig_t, hdr_crc);
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return compute_crc64((const uint8_t *)sig, crc_span);
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}
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homeblocks_sig_result_t homeblocks_sig_check(struct blkio_dev *dev,
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uint32_t sig_start_fblock,
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homeblocks_sig_t *out_sig) {
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uint8_t buf[4096];
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uint32_t i;
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homeblocks_sig_t local;
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uint64_t expected_crc;
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if (!dev) return HOMEBLOCKS_SIG_READ_ERROR;
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/* homeblocks_sig_t is exactly one 4KiB devblock; blkio's own unit is a
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* 1KiB "forth block" (BLKIO_FORTH_BLOCK_SIZE), so the header spans 4
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* consecutive reads starting at sig_start_fblock. */
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for (i = 0; i < 4; i++) {
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if (blkio_read((blkio_dev_t *)dev, sig_start_fblock + i,
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buf + (size_t)i * BLKIO_FORTH_BLOCK_SIZE) != BLKIO_OK) {
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return HOMEBLOCKS_SIG_READ_ERROR;
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}
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}
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/* Copy into a properly-aligned local rather than reinterpreting buf's
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* address directly -- buf is only byte-aligned, and homeblocks_sig_t
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* has uint64_t members; a raw cast would be a strict-aliasing and
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* alignment violation for no benefit over one memcpy. */
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memcpy(&local, buf, sizeof(local));
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if (HOMEBLOCKS_SIG_GET_MAGIC(local.magic) != (uint32_t)(HOMEBLOCKS_SIG_MAGIC & 0xFFFFFFFFULL)) {
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return HOMEBLOCKS_SIG_BLANK;
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}
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if (HOMEBLOCKS_SIG_GET_VERSION(local.magic) != HOMEBLOCKS_SIG_VERSION_0) {
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return HOMEBLOCKS_SIG_BAD_VERSION;
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}
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expected_crc = homeblocks_sig_compute_crc(&local);
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if (expected_crc != local.hdr_crc) {
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return HOMEBLOCKS_SIG_BAD_CRC;
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}
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if (out_sig) *out_sig = local;
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return HOMEBLOCKS_SIG_OK;
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}
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