d7352c0db0
q35 stopped with "no root filesystem" because its disk is SATA, like every PC since 2008, and SchOS only had IDE. And SchFS could only sit on a whole raw device, so nothing could boot from a disk that also carried an ESP. - include/blkdev.h, kernel/dev/blkdev.c: a registry of block devices found at probe time, numbered from 4. A disk's GPT (or MBR) is read when it registers, and each partition becomes a device whose block 0 is the partition's first sector. SchFS needs no format change to live in a partition; a Linux SchFS driver will see the same bytes on /dev/sdX2. SchFS has its own GPT type: 47138FA9-B79C-47A6-9F7D-AC1F7F572D5E. - AHCI driver, written from the AHCI 1.3.1 spec: BIOS handoff, COMRESET when the link is down, IDENTIFY, 48-bit DMA read/write, FLUSH. Completion is polled, so the root disk does not depend on interrupt routing. - USB sticks also register as usb0, so their partitions are found. - The root probe tries registered devices between USB and IDE, SchFS-typed partitions first. - make disk / tools/posix/mkdisk.sh: a GPT image with a 64 MB ESP and a SchFS partition, ready to dd to a stick or a disk. Tested in QEMU q35: the old two-disk setup roots on sata1; disk.img as the only SATA disk roots on sata0p2; disk.img as a USB stick (firmware boots from it) roots on usb0p2. Writes survive sync in each case. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01HH7xukt4aaiGj1nQEAoQf1
73 lines
2.7 KiB
Shell
73 lines
2.7 KiB
Shell
#!/bin/sh
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# SPDX-License-Identifier: GPL-2.0-or-later
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#
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# Build a partitioned SchOS disk: the image a real machine boots from.
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#
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# tools/posix/mkdisk.sh <esp-dir> <schfs.img> <output.img>
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#
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# A GUID partition table with two entries:
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#
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# 1 EFI system partition FAT, holding <esp-dir> (the loader and kernel)
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# 2 SchFS <schfs.img>, byte for byte, typed
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# 47138FA9-B79C-47A6-9F7D-AC1F7F572D5E
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#
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# This is the layout every UEFI machine expects: the firmware finds the ESP by
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# its type and runs EFI/BOOT/BOOTX64.EFI from it, and the kernel finds the root
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# by scanning the same table -- the SchFS type first, anything else after (see
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# rootdev_mount() in kernel/proc/proc.c). Write it to a USB stick or a disk
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# with dd and it boots; attach it to QEMU's q35 as its only disk and it boots
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# the same way.
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#
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# The SchFS partition holds the volume unchanged. A filesystem addresses
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# blocks from the start of whatever it is on, and the kernel hands a partition
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# to it as a device whose block 0 is the partition's first sector -- so the
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# image mkschfs writes for a whole disk is already the right content for a
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# partition, and so is anything a Linux SchFS driver is given as /dev/sdX2.
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#
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# Needs sfdisk (util-linux) and mtools. Nothing here needs root or loop
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# devices: the FAT is built in a file and copied in at its offset.
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set -eu
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esp=$1
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vol=$2
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out=$3
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SCHFS_TYPE=47138FA9-B79C-47A6-9F7D-AC1F7F572D5E
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ESP_TYPE=C12A7328-F81F-11D2-BA4B-00A0C93EC93B
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for t in sfdisk mformat mcopy; do
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command -v $t >/dev/null || { echo "mkdisk: needs $t" >&2; exit 1; }
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done
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# Sizes in 512-byte sectors. The ESP is 64 MB, which leaves room for the
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# kernel to grow by an order of magnitude; partitions start on 1 MB
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# boundaries, which is what every partitioning tool does and what flash
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# media erase in.
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esp_mb=64
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esp_start=2048
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esp_sectors=$((esp_mb * 2048))
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vol_bytes=$(wc -c < "$vol")
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vol_start=$((esp_start + esp_sectors))
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vol_sectors=$(( (vol_bytes + 511) / 512 ))
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# 1 MB at the end for the backup GPT, rounded the same way.
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total=$((vol_start + vol_sectors + 2048))
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rm -f "$out" "$out.esp"
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dd if=/dev/zero of="$out" bs=512 count=0 seek=$total 2>/dev/null
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sfdisk --quiet --label gpt "$out" <<EOF
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start=$esp_start, size=$esp_sectors, type=$ESP_TYPE, name="EFI system"
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start=$vol_start, size=$vol_sectors, type=$SCHFS_TYPE, name="SchOS"
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EOF
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# The ESP, built apart and copied in.
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dd if=/dev/zero of="$out.esp" bs=1M count=$esp_mb 2>/dev/null
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mformat -i "$out.esp" -F -v SCHOS ::
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mcopy -i "$out.esp" -s "$esp"/* ::
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dd if="$out.esp" of="$out" bs=512 seek=$esp_start conv=notrunc 2>/dev/null
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rm -f "$out.esp"
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dd if="$vol" of="$out" bs=512 seek=$vol_start conv=notrunc 2>/dev/null
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echo "mkdisk: $out -- ESP ${esp_mb} MB, SchFS $((vol_bytes >> 20)) MB"
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