From 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 Feb 2023 18:24:12 -0800 Subject: Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next Pull networking updates from Jakub Kicinski: "Core: - Add dedicated kmem_cache for typical/small skb->head, avoid having to access struct page at kfree time, and improve memory use. - Introduce sysctl to set default RPS configuration for new netdevs. - Define Netlink protocol specification format which can be used to describe messages used by each family and auto-generate parsers. Add tools for generating kernel data structures and uAPI headers. - Expose all net/core sysctls inside netns. - Remove 4s sleep in netpoll if carrier is instantly detected on boot. - Add configurable limit of MDB entries per port, and port-vlan. - Continue populating drop reasons throughout the stack. - Retire a handful of legacy Qdiscs and classifiers. Protocols: - Support IPv4 big TCP (TSO frames larger than 64kB). - Add IP_LOCAL_PORT_RANGE socket option, to control local port range on socket by socket basis. - Track and report in procfs number of MPTCP sockets used. - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path manager. - IPv6: don't check net.ipv6.route.max_size and rely on garbage collection to free memory (similarly to IPv4). - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986). - ICMP: add per-rate limit counters. - Add support for user scanning requests in ieee802154. - Remove static WEP support. - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate reporting. - WiFi 7 EHT channel puncturing support (client & AP). BPF: - Add a rbtree data structure following the "next-gen data structure" precedent set by recently added linked list, that is, by using kfunc + kptr instead of adding a new BPF map type. - Expose XDP hints via kfuncs with initial support for RX hash and timestamp metadata. - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to better support decap on GRE tunnel devices not operating in collect metadata. - Improve x86 JIT's codegen for PROBE_MEM runtime error checks. - Remove the need for trace_printk_lock for bpf_trace_printk and bpf_trace_vprintk helpers. - Extend libbpf's bpf_tracing.h support for tracing arguments of kprobes/uprobes and syscall as a special case. - Significantly reduce the search time for module symbols by livepatch and BPF. - Enable cpumasks to be used as kptrs, which is useful for tracing programs tracking which tasks end up running on which CPUs in different time intervals. - Add support for BPF trampoline on s390x and riscv64. - Add capability to export the XDP features supported by the NIC. - Add __bpf_kfunc tag for marking kernel functions as kfuncs. - Add cgroup.memory=nobpf kernel parameter option to disable BPF memory accounting for container environments. Netfilter: - Remove the CLUSTERIP target. It has been marked as obsolete for years, and we still have WARN splats wrt races of the out-of-band /proc interface installed by this target. - Add 'destroy' commands to nf_tables. They are identical to the existing 'delete' commands, but do not return an error if the referenced object (set, chain, rule...) did not exist. Driver API: - Improve cpumask_local_spread() locality to help NICs set the right IRQ affinity on AMD platforms. - Separate C22 and C45 MDIO bus transactions more clearly. - Introduce new DCB table to control DSCP rewrite on egress. - Support configuration of Physical Layer Collision Avoidance (PLCA) Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of shared medium Ethernet. - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing preemption of low priority frames by high priority frames. - Add support for controlling MACSec offload using netlink SET. - Rework devlink instance refcounts to allow registration and de-registration under the instance lock. Split the code into multiple files, drop some of the unnecessarily granular locks and factor out common parts of netlink operation handling. - Add TX frame aggregation parameters (for USB drivers). - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning messages with notifications for debug. - Allow offloading of UDP NEW connections via act_ct. - Add support for per action HW stats in TC. - Support hardware miss to TC action (continue processing in SW from a specific point in the action chain). - Warn if old Wireless Extension user space interface is used with modern cfg80211/mac80211 drivers. Do not support Wireless Extensions for Wi-Fi 7 devices at all. Everyone should switch to using nl80211 interface instead. - Improve the CAN bit timing configuration. Use extack to return error messages directly to user space, update the SJW handling, including the definition of a new default value that will benefit CAN-FD controllers, by increasing their oscillator tolerance. New hardware / drivers: - Ethernet: - nVidia BlueField-3 support (control traffic driver) - Ethernet support for imx93 SoCs - Motorcomm yt8531 gigabit Ethernet PHY - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA) - Microchip LAN8841 PHY (incl. cable diagnostics and PTP) - Amlogic gxl MDIO mux - WiFi: - RealTek RTL8188EU (rtl8xxxu) - Qualcomm Wi-Fi 7 devices (ath12k) - CAN: - Renesas R-Car V4H Drivers: - Bluetooth: - Set Per Platform Antenna Gain (PPAG) for Intel controllers. - Ethernet NICs: - Intel (1G, igc): - support TSN / Qbv / packet scheduling features of i226 model - Intel (100G, ice): - use GNSS subsystem instead of TTY - multi-buffer XDP support - extend support for GPIO pins to E823 devices - nVidia/Mellanox: - update the shared buffer configuration on PFC commands - implement PTP adjphase function for HW offset control - TC support for Geneve and GRE with VF tunnel offload - more efficient crypto key management method - multi-port eswitch support - Netronome/Corigine: - add DCB IEEE support - support IPsec offloading for NFP3800 - Freescale/NXP (enetc): - support XDP_REDIRECT for XDP non-linear buffers - improve reconfig, avoid link flap and waiting for idle - support MAC Merge layer - Other NICs: - sfc/ef100: add basic devlink support for ef100 - ionic: rx_push mode operation (writing descriptors via MMIO) - bnxt: use the auxiliary bus abstraction for RDMA - r8169: disable ASPM and reset bus in case of tx timeout - cpsw: support QSGMII mode for J721e CPSW9G - cpts: support pulse-per-second output - ngbe: add an mdio bus driver - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing - r8152: handle devices with FW with NCM support - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation - virtio-net: support multi buffer XDP - virtio/vsock: replace virtio_vsock_pkt with sk_buff - tsnep: XDP support - Ethernet high-speed switches: - nVidia/Mellanox (mlxsw): - add support for latency TLV (in FW control messages) - Microchip (sparx5): - separate explicit and implicit traffic forwarding rules, make the implicit rules always active - add support for egress DSCP rewrite - IS0 VCAP support (Ingress Classification) - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS etc.) - ES2 VCAP support (Egress Access Control) - support for Per-Stream Filtering and Policing (802.1Q, 8.6.5.1) - Ethernet embedded switches: - Marvell (mv88e6xxx): - add MAB (port auth) offload support - enable PTP receive for mv88e6390 - NXP (ocelot): - support MAC Merge layer - support for the the vsc7512 internal copper phys - Microchip: - lan9303: convert to PHYLINK - lan966x: support TC flower filter statistics - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x - lan937x: support Credit Based Shaper configuration - ksz9477: support Energy Efficient Ethernet - other: - qca8k: convert to regmap read/write API, use bulk operations - rswitch: Improve TX timestamp accuracy - Intel WiFi (iwlwifi): - EHT (Wi-Fi 7) rate reporting - STEP equalizer support: transfer some STEP (connection to radio on platforms with integrated wifi) related parameters from the BIOS to the firmware. - Qualcomm 802.11ax WiFi (ath11k): - IPQ5018 support - Fine Timing Measurement (FTM) responder role support - channel 177 support - MediaTek WiFi (mt76): - per-PHY LED support - mt7996: EHT (Wi-Fi 7) support - Wireless Ethernet Dispatch (WED) reset support - switch to using page pool allocator - RealTek WiFi (rtw89): - support new version of Bluetooth co-existance - Mobile: - rmnet: support TX aggregation" * tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits) page_pool: add a comment explaining the fragment counter usage net: ethtool: fix __ethtool_dev_mm_supported() implementation ethtool: pse-pd: Fix double word in comments xsk: add linux/vmalloc.h to xsk.c sefltests: netdevsim: wait for devlink instance after netns removal selftest: fib_tests: Always cleanup before exit net/mlx5e: Align IPsec ASO result memory to be as required by hardware net/mlx5e: TC, Set CT miss to the specific ct action instance net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG net/mlx5: Refactor tc miss handling to a single function net/mlx5: Kconfig: Make tc offload depend on tc skb extension net/sched: flower: Support hardware miss to tc action net/sched: flower: Move filter handle initialization earlier net/sched: cls_api: Support hardware miss to tc action net/sched: Rename user cookie and act cookie sfc: fix builds without CONFIG_RTC_LIB sfc: clean up some inconsistent indentings net/mlx4_en: Introduce flexible array to silence overflow warning net: lan966x: Fix possible deadlock inside PTP net/ulp: Remove redundant ->clone() test in inet_clone_ulp(). ... --- Documentation/filesystems/romfs.rst | 194 ++++++++++++++++++++++++++++++++++++ 1 file changed, 194 insertions(+) create mode 100644 Documentation/filesystems/romfs.rst (limited to 'Documentation/filesystems/romfs.rst') diff --git a/Documentation/filesystems/romfs.rst b/Documentation/filesystems/romfs.rst new file mode 100644 index 000000000..465b11efa --- /dev/null +++ b/Documentation/filesystems/romfs.rst @@ -0,0 +1,194 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======================= +ROMFS - ROM File System +======================= + +This is a quite dumb, read only filesystem, mainly for initial RAM +disks of installation disks. It has grown up by the need of having +modules linked at boot time. Using this filesystem, you get a very +similar feature, and even the possibility of a small kernel, with a +file system which doesn't take up useful memory from the router +functions in the basement of your office. + +For comparison, both the older minix and xiafs (the latter is now +defunct) filesystems, compiled as module need more than 20000 bytes, +while romfs is less than a page, about 4000 bytes (assuming i586 +code). Under the same conditions, the msdos filesystem would need +about 30K (and does not support device nodes or symlinks), while the +nfs module with nfsroot is about 57K. Furthermore, as a bit unfair +comparison, an actual rescue disk used up 3202 blocks with ext2, while +with romfs, it needed 3079 blocks. + +To create such a file system, you'll need a user program named +genromfs. It is available on http://romfs.sourceforge.net/ + +As the name suggests, romfs could be also used (space-efficiently) on +various read-only media, like (E)EPROM disks if someone will have the +motivation.. :) + +However, the main purpose of romfs is to have a very small kernel, +which has only this filesystem linked in, and then can load any module +later, with the current module utilities. It can also be used to run +some program to decide if you need SCSI devices, and even IDE or +floppy drives can be loaded later if you use the "initrd"--initial +RAM disk--feature of the kernel. This would not be really news +flash, but with romfs, you can even spare off your ext2 or minix or +maybe even affs filesystem until you really know that you need it. + +For example, a distribution boot disk can contain only the cd disk +drivers (and possibly the SCSI drivers), and the ISO 9660 filesystem +module. The kernel can be small enough, since it doesn't have other +filesystems, like the quite large ext2fs module, which can then be +loaded off the CD at a later stage of the installation. Another use +would be for a recovery disk, when you are reinstalling a workstation +from the network, and you will have all the tools/modules available +from a nearby server, so you don't want to carry two disks for this +purpose, just because it won't fit into ext2. + +romfs operates on block devices as you can expect, and the underlying +structure is very simple. Every accessible structure begins on 16 +byte boundaries for fast access. The minimum space a file will take +is 32 bytes (this is an empty file, with a less than 16 character +name). The maximum overhead for any non-empty file is the header, and +the 16 byte padding for the name and the contents, also 16+14+15 = 45 +bytes. This is quite rare however, since most file names are longer +than 3 bytes, and shorter than 15 bytes. + +The layout of the filesystem is the following:: + + offset content + + +---+---+---+---+ + 0 | - | r | o | m | \ + +---+---+---+---+ The ASCII representation of those bytes + 4 | 1 | f | s | - | / (i.e. "-rom1fs-") + +---+---+---+---+ + 8 | full size | The number of accessible bytes in this fs. + +---+---+---+---+ + 12 | checksum | The checksum of the FIRST 512 BYTES. + +---+---+---+---+ + 16 | volume name | The zero terminated name of the volume, + : : padded to 16 byte boundary. + +---+---+---+---+ + xx | file | + : headers : + +Every multi byte value (32 bit words, I'll use the longwords term from +now on) must be in big endian order. + +The first eight bytes identify the filesystem, even for the casual +inspector. After that, in the 3rd longword, it contains the number of +bytes accessible from the start of this filesystem. The 4th longword +is the checksum of the first 512 bytes (or the number of bytes +accessible, whichever is smaller). The applied algorithm is the same +as in the AFFS filesystem, namely a simple sum of the longwords +(assuming bigendian quantities again). For details, please consult +the source. This algorithm was chosen because although it's not quite +reliable, it does not require any tables, and it is very simple. + +The following bytes are now part of the file system; each file header +must begin on a 16 byte boundary:: + + offset content + + +---+---+---+---+ + 0 | next filehdr|X| The offset of the next file header + +---+---+---+---+ (zero if no more files) + 4 | spec.info | Info for directories/hard links/devices + +---+---+---+---+ + 8 | size | The size of this file in bytes + +---+---+---+---+ + 12 | checksum | Covering the meta data, including the file + +---+---+---+---+ name, and padding + 16 | file name | The zero terminated name of the file, + : : padded to 16 byte boundary + +---+---+---+---+ + xx | file data | + : : + +Since the file headers begin always at a 16 byte boundary, the lowest +4 bits would be always zero in the next filehdr pointer. These four +bits are used for the mode information. Bits 0..2 specify the type of +the file; while bit 4 shows if the file is executable or not. The +permissions are assumed to be world readable, if this bit is not set, +and world executable if it is; except the character and block devices, +they are never accessible for other than owner. The owner of every +file is user and group 0, this should never be a problem for the +intended use. The mapping of the 8 possible values to file types is +the following: + +== =============== ============================================ + mapping spec.info means +== =============== ============================================ + 0 hard link link destination [file header] + 1 directory first file's header + 2 regular file unused, must be zero [MBZ] + 3 symbolic link unused, MBZ (file data is the link content) + 4 block device 16/16 bits major/minor number + 5 char device - " - + 6 socket unused, MBZ + 7 fifo unused, MBZ +== =============== ============================================ + +Note that hard links are specifically marked in this filesystem, but +they will behave as you can expect (i.e. share the inode number). +Note also that it is your responsibility to not create hard link +loops, and creating all the . and .. links for directories. This is +normally done correctly by the genromfs program. Please refrain from +using the executable bits for special purposes on the socket and fifo +special files, they may have other uses in the future. Additionally, +please remember that only regular files, and symlinks are supposed to +have a nonzero size field; they contain the number of bytes available +directly after the (padded) file name. + +Another thing to note is that romfs works on file headers and data +aligned to 16 byte boundaries, but most hardware devices and the block +device drivers are unable to cope with smaller than block-sized data. +To overcome this limitation, the whole size of the file system must be +padded to an 1024 byte boundary. + +If you have any problems or suggestions concerning this file system, +please contact me. However, think twice before wanting me to add +features and code, because the primary and most important advantage of +this file system is the small code. On the other hand, don't be +alarmed, I'm not getting that much romfs related mail. Now I can +understand why Avery wrote poems in the ARCnet docs to get some more +feedback. :) + +romfs has also a mailing list, and to date, it hasn't received any +traffic, so you are welcome to join it to discuss your ideas. :) + +It's run by ezmlm, so you can subscribe to it by sending a message +to romfs-subscribe@shadow.banki.hu, the content is irrelevant. + +Pending issues: + +- Permissions and owner information are pretty essential features of a + Un*x like system, but romfs does not provide the full possibilities. + I have never found this limiting, but others might. + +- The file system is read only, so it can be very small, but in case + one would want to write _anything_ to a file system, he still needs + a writable file system, thus negating the size advantages. Possible + solutions: implement write access as a compile-time option, or a new, + similarly small writable filesystem for RAM disks. + +- Since the files are only required to have alignment on a 16 byte + boundary, it is currently possibly suboptimal to read or execute files + from the filesystem. It might be resolved by reordering file data to + have most of it (i.e. except the start and the end) laying at "natural" + boundaries, thus it would be possible to directly map a big portion of + the file contents to the mm subsystem. + +- Compression might be an useful feature, but memory is quite a + limiting factor in my eyes. + +- Where it is used? + +- Does it work on other architectures than intel and motorola? + + +Have fun, + +Janos Farkas -- cgit v1.2.3