hwreport: describe a machine onto a USB stick, from a Linux-style /sys
hwreport writes one folder to the first read-write FAT mount, or mounts the first USB stick that takes vfat itself and unmounts it afterwards: summary.txt (machine, firmware, CPU, memory, every PCI and USB device with its driver or "-- no driver"), dmesg.txt, lspci.txt in the shape of lspci -nnk -xxx, lsusb.txt, dmi.txt, memmap.txt, the ACPI tables as raw .dat files iasl -d reads, and copies of /proc. Serials, the UUID and the MSDM/SLIC tables (a Windows licence key) are left out. It reads /sys, which is new: sysfs at Linux's paths and in Linux's formats -- /sys/bus/pci/devices with uevent, config and resource, /sys/bus/usb/devices, /sys/firmware/acpi/tables, dmi/tables, memmap and efi, /sys/class/dmi/id. toybox's lspci and lsusb work unmodified against it. The USB core now keeps a table of attached devices for it. The machine's name comes from SMBIOS (kernel/dev/dmi.c). The UEFI loader hands over the entry point from the configuration table, the kernel falls back to the 0xF0000 scan, and the log gets Linux's "DMI:" line. Two bugs found on the way: - The loader handed over at most 40 memory-map entries, in firmware order. A laptop's UEFI map is 60-150 descriptors with RAM above 4 GB listed last, so that is what was dropped. The entries now have their own area at 0x31000 with room for 256, are sorted before merging, and the kernel's 32 usable regions keep the largest when there are more. - MemTotal and sysinfo's totalram were PHYSTOP, an address, which counts the PCI hole: a 6 GB machine reported 8. Now the usable RAM, summed. usb.ids moves to /usr/share/hwdata, where lsusb looks for it, and pci.ids joins it (`make pci-ids`, BSD-3-Clause like usb.ids). Checked under QEMU q35: the report written to a FAT32 stick, fsck.fat clean, DSDT.dat disassembled by iasl on the host, lspci -k and lsusb showing names, 6 GB of RAM seen as 6137 MB. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
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@ -119,8 +119,8 @@ during path resolution. `/proc` is mounted by init:
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mount("proc", "/proc", "proc", 0, 0);
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```
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The filesystem types are `proc`, `devtmpfs`, `schfs` and `vfat` (also accepted
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as `msdos` and `fat`). Unmounting a FAT volume while anything on it is open, or
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The filesystem types are `proc`, `devtmpfs`, `sysfs`, `schfs` and `vfat` (also
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accepted as `msdos` and `fat`). Unmounting a FAT volume while anything on it is open, or
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is some process's working directory, fails with `EBUSY`.
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## procfs
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@ -222,6 +222,46 @@ selftest, `t` text specimen, `n` the netdev ARP selftest.
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---
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## sysfs
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`/sys`, in Linux's layout for the parts that exist here. `kernel/fs/sysfs.c`,
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mounted by init with `mount("sysfs", "/sys", "sysfs", 0, 0)`.
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| path | contents |
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|------|----------|
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| `/sys/bus/pci/devices/0000:BB:DD.F/` | `vendor device class revision subsystem_vendor subsystem_device irq resource config uevent` |
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| `/sys/bus/usb/devices/B-P[.P...]/` | `idVendor idProduct bcdDevice busnum devnum speed bDeviceClass bDeviceSubClass bDeviceProtocol bNumConfigurations uevent` |
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| `/sys/firmware/acpi/tables/` | each ACPI table, raw; a repeated signature is numbered from 1 (`SSDT1`, `SSDT2`) |
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| `/sys/firmware/dmi/tables/` | `smbios_entry_point` and `DMI`, raw |
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| `/sys/firmware/memmap/N/` | `start end type`, the firmware's map as the loader handed it over |
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| `/sys/firmware/efi/` | present when UEFI booted the kernel; empty |
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| `/sys/class/dmi/id/` | `sys_vendor product_name product_version board_name bios_version`, and the rest Linux has, except serials and the UUID |
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**Linux's layout because everything that reads hardware reads it from there.**
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toybox's `lspci` and `lsusb` walk `/sys/bus/*/devices` and parse each `uevent`
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(`DRIVER=`, `PCI_ID=`, `PRODUCT=`, `BUSNUM=`), so with these files they work
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unmodified, with names from `/usr/share/hwdata/pci.ids` and `usb.ids`. Formats
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follow Linux to the character: `0x8086` in `vendor`, `%04x` in `idVendor`,
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`PCI_CLASS` in upper case.
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Like `/proc`, nothing is stored: a listing comes from the live PCI list, the
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USB core's table of attached devices, the ACPI root table and the SMBIOS table
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at the moment it is read, so a stick shows up in `/sys/bus/usb/devices` as soon
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as it is attached. Text files report size 0, as `/proc`'s do; binary ones (the
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tables, `config`) report their real length, since tools copy them by it.
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What is missing, compared with Linux: `/sys/devices` and its symlinks (the
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`bus/*/devices` entries are directories rather than links into it),
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`/sys/class` beyond `dmi`, `/sys/block`, and anything writable. PCI `config` is
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256 bytes, because config space is read through port `0xCF8`, which reaches
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no further.
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The machine's identity comes from SMBIOS (`kernel/dev/dmi.c`): the UEFI loader
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hands over the entry point from the firmware's configuration table, and the
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kernel falls back to scanning `0xF0000`-`0xFFFFF`. The boot log carries Linux's
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line for it, `DMI: <vendor> <product>/<board>, BIOS <version> <date>`.
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## Errno, and why `return -1` is a bug
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A syscall that fails returns a negative errno. `-1` is therefore **`-EPERM`**,
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