df1394eaa3
SCFF, the SchOS Compressed File Format (include/fs/scff.h), is a block image cut into 128 KB chunks, each its own zstd frame, behind an index. tools/mkscff writes it from fs-ram.img on every core (-19, 11 s) and checks each chunk decompresses to itself. The kernel carries the .scff as its ramdisk and unpacks a chunk the first time a block in it is read; zero blocks share one page. The kernel and the ISO are the compressed size, and the root costs memory only for what is touched. See docs/architecture/scff.md. zstd 1.5.7 comes from ports/zstd like uACPI: the decoder is compiled into the kernel at -O2, with a static context and a 64 KB stack of its own, and mkscff builds the whole library from the same release. world now has xorg-server, the fbdev and evdev drivers, xinit, Window Maker, xterm and DejaVu, and /root/.xinitrc runs wmaker. That root is 358 MB, 102 MB as SCFF. The ISO no longer carries the root a third time as an ISO 9660 tree, which nothing read. schos.iso: 1389 MB -> 318 MB. El Torito keeps its own copy of the EFI image, the layout real machines have booted. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
198 lines
9.2 KiB
Shell
198 lines
9.2 KiB
Shell
#!/bin/sh
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# Build a bootable SchOS ISO.
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#
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# tools/posix/mkiso.sh [output.iso]
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#
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# The disc carries one El Torito boot entry and the loader and kernel as files:
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#
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# /boot/efiboot.img a FAT image holding the loader and the kernel
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# /EFI/BOOT/BOOTX64.EFI the same loader, visible as a file on the disc
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# /schos/kernel the same kernel, for chainloaders (below)
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#
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# The root filesystem is inside the kernel, as its ramdisk. The disc used to
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# carry it a third time as an ISO 9660 tree, which nothing reads -- SchOS has
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# no ISO 9660 driver -- and once Xorg was in the root that copy alone was
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# 360 MB.
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#
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# --- Why only one entry -----------------------------------------------------
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#
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# There was a second, for BIOS: cdboot and stage2 concatenated with the kernel
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# and loaded by El Torito in no-emulation mode. The BIOS loader is gone, so the
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# entry that started it is too.
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#
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# What UEFI wants is not that mechanism at all. Firmware does not run
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# no-emulation boot code; it looks for a FAT filesystem containing
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# EFI/BOOT/BOOTX64.EFI and hands that volume to the application it finds. So
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# the entry is a FAT image built with mtools, and it carries the kernel as well
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# as the loader -- BOOTX64.EFI opens \schos\kernel on the volume it was itself
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# loaded from, and for a UEFI boot that volume is this FAT image, not the ISO
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# 9660 tree around it. Without the kernel in here the loader comes up and halts
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# with EFI_NOT_FOUND, which is what it did.
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#
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# The loader is also copied into the ISO tree at /EFI/BOOT/BOOTX64.EFI, because
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# some firmware looks there directly when booting from a USB stick.
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#
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# --- Booting from a USB stick -----------------------------------------------
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#
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# -isohybrid-gpt-basdat adds a GPT that marks the FAT image as a basic data
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# partition, so writing this .iso to a stick with dd produces something UEFI
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# will boot. That was already the only arrangement that worked from a stick:
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# the firmware presents the medium as a hard disk, while the BIOS loader read
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# the kernel back over ATAPI, so it never booted this way even when it existed.
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#
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# --- Rock Ridge and Joliet --------------------------------------------------
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#
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# Plain ISO 9660 gives 8.3 uppercase names with no permissions, so the sysroot
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# would arrive as /BIN/TOYBOX.;1 with every file marked the same. Rock Ridge
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# restores POSIX names, permissions and symlinks for Unix readers; Joliet does
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# long names for Windows. Both are additions to the same image -- a reader that
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# understands neither still sees a valid, if ugly, ISO 9660 disc.
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#
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# -cache-inodes matters more than it looks: the sysroot is a toybox multicall
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# binary with a couple of hundred hard links to it. Without inode caching each
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# link becomes its own copy and the disc grows by two orders of magnitude.
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set -e
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# Run from anywhere: resolve the repo root from this script's own location
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# rather than trusting the caller's working directory. Everything below is
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# relative to it, and running from tools/posix/ used to fail with "missing
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# build/kernel/kernel -- run make first" on a tree that was perfectly built.
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script_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
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repo=$(CDPATH= cd -- "$script_dir/../.." && pwd)
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# An output path given on the command line means where the *caller* is, not
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# where the repo is, so it is made absolute before the cd below moves the goal
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# posts under it. Without an argument the disc lands at the repo root, which is
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# where `make iso` has always put it.
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invoked_from=$(pwd)
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OUT=${1:-schos.iso}
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case $OUT in
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/*) ;;
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*) OUT=$invoked_from/$OUT ;;
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esac
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cd "$repo"
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BUILD=${BUILD:-build}
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STAGING="$BUILD/iso"
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KERNEL="$BUILD/kernel/kernel"
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EFIAPP="$BUILD/uefi/BOOTX64.EFI"
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[ -f "$KERNEL" ] || { echo "mkiso: missing $KERNEL -- run make first" >&2; exit 1; }
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[ -f "$EFIAPP" ] || { echo "mkiso: missing $EFIAPP -- run 'make uefi' first" >&2; exit 1; }
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# mtools is not optional any more. It used to be: without it the disc fell back
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# to being BIOS-only, which was a degraded disc rather than no disc. There is no
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# other entry to fall back to now, so a missing mformat means the ISO would not
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# boot anything, and failing here says so instead of shipping it.
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if ! command -v mformat >/dev/null 2>&1 || ! command -v mcopy >/dev/null 2>&1; then
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echo "mkiso: need mtools (mformat, mcopy) to build the EFI system partition" >&2
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echo " Fedora: sudo dnf install mtools" >&2
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echo " Debian/Ubuntu: apt install mtools" >&2
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exit 1
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fi
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rm -rf "$STAGING"
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mkdir -p "$STAGING/boot" "$STAGING/EFI/BOOT" "$STAGING/schos"
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cp "$EFIAPP" "$STAGING/EFI/BOOT/BOOTX64.EFI"
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# The kernel in the ISO 9660 tree as well as inside the FAT image.
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#
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# Not redundancy for its own sake: it depends on who loaded us. Booting the
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# disc directly, firmware runs the El Torito FAT image and the loader opens
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# \schos\kernel on that volume. But a chainloader -- Ventoy is the common one
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# -- ignores El Torito entirely, mounts the ISO 9660 tree and runs
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# \EFI\BOOT\BOOTX64.EFI from *there*. The loader then looks for the kernel on
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# the volume it was itself loaded from, which is now the ISO tree, and a disc
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# with the kernel only in the FAT image cannot answer.
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#
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# The symptom is precise and was reported from a real machine: the loader comes
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# up, draws its menu, and then dies with EFI_NOT_FOUND.
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cp "$KERNEL" "$STAGING/schos/kernel"
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# The FAT image for the UEFI El Torito entry.
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#
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# It carries the kernel as well as the loader. BOOTX64.EFI opens \schos\kernel
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# on the volume it was itself loaded from, and for a UEFI boot that volume is
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# this FAT image -- not the ISO 9660 tree around it. Without the kernel in here
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# the loader comes up and halts with EFI_NOT_FOUND, which is what it did.
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#
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# Sized from what actually goes in plus slack, rather than fixed: a hardcoded
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# size is a thing that breaks quietly the first time the kernel grows.
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EFI_IMG="$STAGING/boot/efiboot.img"
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payload_kb=$(( ( $(wc -c < "$EFIAPP") + $(wc -c < "$KERNEL") + 1023 ) / 1024 ))
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img_kb=$(( ( (payload_kb + 512 + 31) / 32 ) * 32 ))
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# FAT16, chosen by cluster count: a firmware decides FAT12/16/32 from the
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# number of clusters alone, as the spec says to, and FAT12 is the type older
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# firmware is least likely to read on a removable disk. So at least 8 MB, and
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# the smallest power-of-two cluster that keeps the count under FAT16's 65525.
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[ "$img_kb" -lt 8192 ] && img_kb=8192
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spc=1
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while [ $(( img_kb * 2 / spc )) -gt 65000 ]; do spc=$(( spc * 2 )); done
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rm -f "$EFI_IMG"
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if true; then
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# Create the file first and format it with an explicit geometry.
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#
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# Not `mformat -f`: that takes one of the standard floppy capacities
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# (360, 720, 1440, 2880 KB) and rejects anything else -- "Bad size 512".
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# Giving heads, sectors-per-track and a total sector count instead lets the
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# image be whatever the loader actually needs, which is the point of sizing
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# it from the file rather than hardcoding 1.44 MB.
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dd if=/dev/zero of="$EFI_IMG" bs=1024 count="$img_kb" status=none
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mformat -i "$EFI_IMG" -h 64 -s 32 -c $spc -T $((img_kb * 2)) ::
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mmd -i "$EFI_IMG" ::/EFI ::/EFI/BOOT ::/schos
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mcopy -i "$EFI_IMG" "$EFIAPP" ::/EFI/BOOT/BOOTX64.EFI
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mcopy -i "$EFI_IMG" "$KERNEL" ::/schos/kernel
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fi
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# xorriso if it is here, mkisofs otherwise. Both accept the El Torito flags
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# below unchanged -- xorriso's -as mkisofs mode exists precisely to be
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# argument-compatible with it. The fallback is not academic: there is no xorriso
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# package for Windows in scoop, where this is developed, but cdrtools provides
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# mkisofs.exe.
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if command -v xorriso >/dev/null 2>&1; then
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MKISOFS="xorriso -as mkisofs"
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# The same FAT image again, as a partition of its own in an MBR.
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#
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# This used to be -isohybrid-gpt-basdat, which does nothing without an
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# MBR template (-isohybrid-mbr) -- so the ISO had no partition table at
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# all, and written to a stick it was a CD filesystem at sector 0. A
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# B550's firmware reads that as though it were a disc and boots it; an
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# HP all-in-one from 2012 looks for an EFI system partition on a USB
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# disk, finds none, and lists the stick under Legacy only. A partition
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# of type 0xEF is what every UEFI firmware looks for on a removable
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# disk, MBR rather than GPT because the oldest ones read that best.
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HYBRID="-append_partition 2 0xef $EFI_IMG"
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# El Torito keeps its own copy of the image in the tree, the layout real
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# machines have booted. Pointing it into the partition instead
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# (--interval:appended_partition_2:all::, as Arch does) saves a copy, and
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# an ASUS laptop stopped listing the stick the day that was tried. With
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# the root compressed (SCFF) the copy is only the kernel's size.
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elif command -v mkisofs >/dev/null 2>&1; then
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MKISOFS="mkisofs"
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HYBRID=""
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else
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echo "mkiso: need xorriso or mkisofs on PATH" >&2
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echo " Windows: scoop install cdrtools" >&2
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echo " Debian/Ubuntu: apt install xorriso" >&2
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exit 1
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fi
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# shellcheck disable=SC2086 # EFI_ARGS is a deliberate word list
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$MKISOFS \
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-quiet \
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-V SCHOS \
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-A "SchOS" \
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-R -J -joliet-long \
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-cache-inodes \
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-e boot/efiboot.img \
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-no-emul-boot \
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$HYBRID \
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-o "$OUT" \
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"$STAGING"
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echo "==> $OUT ($(wc -c < "$OUT") bytes)"
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echo " UEFI: qemu-system-x86_64 -bios OVMF_CODE.fd -cdrom $OUT"
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echo " USB: dd if=$OUT of=/dev/sdX bs=4M"
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