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author | 2023-02-21 18:24:12 -0800 | |
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committer | 2023-02-21 18:24:12 -0800 | |
commit | 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch) | |
tree | cc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/core-api/asm-annotations.rst | |
download | linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip |
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
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().
...
Diffstat (limited to 'Documentation/core-api/asm-annotations.rst')
-rw-r--r-- | Documentation/core-api/asm-annotations.rst | 222 |
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diff --git a/Documentation/core-api/asm-annotations.rst b/Documentation/core-api/asm-annotations.rst new file mode 100644 index 000000000..bc514ed59 --- /dev/null +++ b/Documentation/core-api/asm-annotations.rst @@ -0,0 +1,222 @@ +Assembler Annotations +===================== + +Copyright (c) 2017-2019 Jiri Slaby + +This document describes the new macros for annotation of data and code in +assembly. In particular, it contains information about ``SYM_FUNC_START``, +``SYM_FUNC_END``, ``SYM_CODE_START``, and similar. + +Rationale +--------- +Some code like entries, trampolines, or boot code needs to be written in +assembly. The same as in C, such code is grouped into functions and +accompanied with data. Standard assemblers do not force users into precisely +marking these pieces as code, data, or even specifying their length. +Nevertheless, assemblers provide developers with such annotations to aid +debuggers throughout assembly. On top of that, developers also want to mark +some functions as *global* in order to be visible outside of their translation +units. + +Over time, the Linux kernel has adopted macros from various projects (like +``binutils``) to facilitate such annotations. So for historic reasons, +developers have been using ``ENTRY``, ``END``, ``ENDPROC``, and other +annotations in assembly. Due to the lack of their documentation, the macros +are used in rather wrong contexts at some locations. Clearly, ``ENTRY`` was +intended to denote the beginning of global symbols (be it data or code). +``END`` used to mark the end of data or end of special functions with +*non-standard* calling convention. In contrast, ``ENDPROC`` should annotate +only ends of *standard* functions. + +When these macros are used correctly, they help assemblers generate a nice +object with both sizes and types set correctly. For example, the result of +``arch/x86/lib/putuser.S``:: + + Num: Value Size Type Bind Vis Ndx Name + 25: 0000000000000000 33 FUNC GLOBAL DEFAULT 1 __put_user_1 + 29: 0000000000000030 37 FUNC GLOBAL DEFAULT 1 __put_user_2 + 32: 0000000000000060 36 FUNC GLOBAL DEFAULT 1 __put_user_4 + 35: 0000000000000090 37 FUNC GLOBAL DEFAULT 1 __put_user_8 + +This is not only important for debugging purposes. When there are properly +annotated objects like this, tools can be run on them to generate more useful +information. In particular, on properly annotated objects, ``objtool`` can be +run to check and fix the object if needed. Currently, ``objtool`` can report +missing frame pointer setup/destruction in functions. It can also +automatically generate annotations for the ORC unwinder +(Documentation/x86/orc-unwinder.rst) +for most code. Both of these are especially important to support reliable +stack traces which are in turn necessary for kernel live patching +(Documentation/livepatch/livepatch.rst). + +Caveat and Discussion +--------------------- +As one might realize, there were only three macros previously. That is indeed +insufficient to cover all the combinations of cases: + +* standard/non-standard function +* code/data +* global/local symbol + +There was a discussion_ and instead of extending the current ``ENTRY/END*`` +macros, it was decided that brand new macros should be introduced instead:: + + So how about using macro names that actually show the purpose, instead + of importing all the crappy, historic, essentially randomly chosen + debug symbol macro names from the binutils and older kernels? + +.. _discussion: https://lore.kernel.org/r/20170217104757.28588-1-jslaby@suse.cz + +Macros Description +------------------ + +The new macros are prefixed with the ``SYM_`` prefix and can be divided into +three main groups: + +1. ``SYM_FUNC_*`` -- to annotate C-like functions. This means functions with + standard C calling conventions. For example, on x86, this means that the + stack contains a return address at the predefined place and a return from + the function can happen in a standard way. When frame pointers are enabled, + save/restore of frame pointer shall happen at the start/end of a function, + respectively, too. + + Checking tools like ``objtool`` should ensure such marked functions conform + to these rules. The tools can also easily annotate these functions with + debugging information (like *ORC data*) automatically. + +2. ``SYM_CODE_*`` -- special functions called with special stack. Be it + interrupt handlers with special stack content, trampolines, or startup + functions. + + Checking tools mostly ignore checking of these functions. But some debug + information still can be generated automatically. For correct debug data, + this code needs hints like ``UNWIND_HINT_REGS`` provided by developers. + +3. ``SYM_DATA*`` -- obviously data belonging to ``.data`` sections and not to + ``.text``. Data do not contain instructions, so they have to be treated + specially by the tools: they should not treat the bytes as instructions, + nor assign any debug information to them. + +Instruction Macros +~~~~~~~~~~~~~~~~~~ +This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated above. + +``objtool`` requires that all code must be contained in an ELF symbol. Symbol +names that have a ``.L`` prefix do not emit symbol table entries. ``.L`` +prefixed symbols can be used within a code region, but should be avoided for +denoting a range of code via ``SYM_*_START/END`` annotations. + +* ``SYM_FUNC_START`` and ``SYM_FUNC_START_LOCAL`` are supposed to be **the + most frequent markings**. They are used for functions with standard calling + conventions -- global and local. Like in C, they both align the functions to + architecture specific ``__ALIGN`` bytes. There are also ``_NOALIGN`` variants + for special cases where developers do not want this implicit alignment. + + ``SYM_FUNC_START_WEAK`` and ``SYM_FUNC_START_WEAK_NOALIGN`` markings are + also offered as an assembler counterpart to the *weak* attribute known from + C. + + All of these **shall** be coupled with ``SYM_FUNC_END``. First, it marks + the sequence of instructions as a function and computes its size to the + generated object file. Second, it also eases checking and processing such + object files as the tools can trivially find exact function boundaries. + + So in most cases, developers should write something like in the following + example, having some asm instructions in between the macros, of course:: + + SYM_FUNC_START(memset) + ... asm insns ... + SYM_FUNC_END(memset) + + In fact, this kind of annotation corresponds to the now deprecated ``ENTRY`` + and ``ENDPROC`` macros. + +* ``SYM_FUNC_ALIAS``, ``SYM_FUNC_ALIAS_LOCAL``, and ``SYM_FUNC_ALIAS_WEAK`` can + be used to define multiple names for a function. The typical use is:: + + SYM_FUNC_START(__memset) + ... asm insns ... + SYN_FUNC_END(__memset) + SYM_FUNC_ALIAS(memset, __memset) + + In this example, one can call ``__memset`` or ``memset`` with the same + result, except the debug information for the instructions is generated to + the object file only once -- for the non-``ALIAS`` case. + +* ``SYM_CODE_START`` and ``SYM_CODE_START_LOCAL`` should be used only in + special cases -- if you know what you are doing. This is used exclusively + for interrupt handlers and similar where the calling convention is not the C + one. ``_NOALIGN`` variants exist too. The use is the same as for the ``FUNC`` + category above:: + + SYM_CODE_START_LOCAL(bad_put_user) + ... asm insns ... + SYM_CODE_END(bad_put_user) + + Again, every ``SYM_CODE_START*`` **shall** be coupled by ``SYM_CODE_END``. + + To some extent, this category corresponds to deprecated ``ENTRY`` and + ``END``. Except ``END`` had several other meanings too. + +* ``SYM_INNER_LABEL*`` is used to denote a label inside some + ``SYM_{CODE,FUNC}_START`` and ``SYM_{CODE,FUNC}_END``. They are very similar + to C labels, except they can be made global. An example of use:: + + SYM_CODE_START(ftrace_caller) + /* save_mcount_regs fills in first two parameters */ + ... + + SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) + /* Load the ftrace_ops into the 3rd parameter */ + ... + + SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL) + call ftrace_stub + ... + retq + SYM_CODE_END(ftrace_caller) + +Data Macros +~~~~~~~~~~~ +Similar to instructions, there is a couple of macros to describe data in the +assembly. + +* ``SYM_DATA_START`` and ``SYM_DATA_START_LOCAL`` mark the start of some data + and shall be used in conjunction with either ``SYM_DATA_END``, or + ``SYM_DATA_END_LABEL``. The latter adds also a label to the end, so that + people can use ``lstack`` and (local) ``lstack_end`` in the following + example:: + + SYM_DATA_START_LOCAL(lstack) + .skip 4096 + SYM_DATA_END_LABEL(lstack, SYM_L_LOCAL, lstack_end) + +* ``SYM_DATA`` and ``SYM_DATA_LOCAL`` are variants for simple, mostly one-line + data:: + + SYM_DATA(HEAP, .long rm_heap) + SYM_DATA(heap_end, .long rm_stack) + + In the end, they expand to ``SYM_DATA_START`` with ``SYM_DATA_END`` + internally. + +Support Macros +~~~~~~~~~~~~~~ +All the above reduce themselves to some invocation of ``SYM_START``, +``SYM_END``, or ``SYM_ENTRY`` at last. Normally, developers should avoid using +these. + +Further, in the above examples, one could see ``SYM_L_LOCAL``. There are also +``SYM_L_GLOBAL`` and ``SYM_L_WEAK``. All are intended to denote linkage of a +symbol marked by them. They are used either in ``_LABEL`` variants of the +earlier macros, or in ``SYM_START``. + + +Overriding Macros +~~~~~~~~~~~~~~~~~ +Architecture can also override any of the macros in their own +``asm/linkage.h``, including macros specifying the type of a symbol +(``SYM_T_FUNC``, ``SYM_T_OBJECT``, and ``SYM_T_NONE``). As every macro +described in this file is surrounded by ``#ifdef`` + ``#endif``, it is enough +to define the macros differently in the aforementioned architecture-dependent +header. |