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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/trace/user_events.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/trace/user_events.rst')
-rw-r--r-- | Documentation/trace/user_events.rst | 238 |
1 files changed, 238 insertions, 0 deletions
diff --git a/Documentation/trace/user_events.rst b/Documentation/trace/user_events.rst new file mode 100644 index 000000000..9f181f342 --- /dev/null +++ b/Documentation/trace/user_events.rst @@ -0,0 +1,238 @@ +========================================= +user_events: User-based Event Tracing +========================================= + +:Author: Beau Belgrave + +Overview +-------- +User based trace events allow user processes to create events and trace data +that can be viewed via existing tools, such as ftrace and perf. +To enable this feature, build your kernel with CONFIG_USER_EVENTS=y. + +Programs can view status of the events via +/sys/kernel/debug/tracing/user_events_status and can both register and write +data out via /sys/kernel/debug/tracing/user_events_data. + +Programs can also use /sys/kernel/debug/tracing/dynamic_events to register and +delete user based events via the u: prefix. The format of the command to +dynamic_events is the same as the ioctl with the u: prefix applied. + +Typically programs will register a set of events that they wish to expose to +tools that can read trace_events (such as ftrace and perf). The registration +process gives back two ints to the program for each event. The first int is +the status bit. This describes which bit in little-endian format in the +/sys/kernel/debug/tracing/user_events_status file represents this event. The +second int is the write index which describes the data when a write() or +writev() is called on the /sys/kernel/debug/tracing/user_events_data file. + +The structures referenced in this document are contained within the +/include/uapi/linux/user_events.h file in the source tree. + +**NOTE:** *Both user_events_status and user_events_data are under the tracefs +filesystem and may be mounted at different paths than above.* + +Registering +----------- +Registering within a user process is done via ioctl() out to the +/sys/kernel/debug/tracing/user_events_data file. The command to issue is +DIAG_IOCSREG. + +This command takes a packed struct user_reg as an argument:: + + struct user_reg { + u32 size; + u64 name_args; + u32 status_bit; + u32 write_index; + }; + +The struct user_reg requires two inputs, the first is the size of the structure +to ensure forward and backward compatibility. The second is the command string +to issue for registering. Upon success two outputs are set, the status bit +and the write index. + +User based events show up under tracefs like any other event under the +subsystem named "user_events". This means tools that wish to attach to the +events need to use /sys/kernel/debug/tracing/events/user_events/[name]/enable +or perf record -e user_events:[name] when attaching/recording. + +**NOTE:** *The write_index returned is only valid for the FD that was used* + +Command Format +^^^^^^^^^^^^^^ +The command string format is as follows:: + + name[:FLAG1[,FLAG2...]] [Field1[;Field2...]] + +Supported Flags +^^^^^^^^^^^^^^^ +None yet + +Field Format +^^^^^^^^^^^^ +:: + + type name [size] + +Basic types are supported (__data_loc, u32, u64, int, char, char[20], etc). +User programs are encouraged to use clearly sized types like u32. + +**NOTE:** *Long is not supported since size can vary between user and kernel.* + +The size is only valid for types that start with a struct prefix. +This allows user programs to describe custom structs out to tools, if required. + +For example, a struct in C that looks like this:: + + struct mytype { + char data[20]; + }; + +Would be represented by the following field:: + + struct mytype myname 20 + +Deleting +----------- +Deleting an event from within a user process is done via ioctl() out to the +/sys/kernel/debug/tracing/user_events_data file. The command to issue is +DIAG_IOCSDEL. + +This command only requires a single string specifying the event to delete by +its name. Delete will only succeed if there are no references left to the +event (in both user and kernel space). User programs should use a separate file +to request deletes than the one used for registration due to this. + +Status +------ +When tools attach/record user based events the status of the event is updated +in realtime. This allows user programs to only incur the cost of the write() or +writev() calls when something is actively attached to the event. + +User programs call mmap() on /sys/kernel/debug/tracing/user_events_status to +check the status for each event that is registered. The bit to check in the +file is given back after the register ioctl() via user_reg.status_bit. The bit +is always in little-endian format. Programs can check if the bit is set either +using a byte-wise index with a mask or a long-wise index with a little-endian +mask. + +Currently the size of user_events_status is a single page, however, custom +kernel configurations can change this size to allow more user based events. In +all cases the size of the file is a multiple of a page size. + +For example, if the register ioctl() gives back a status_bit of 3 you would +check byte 0 (3 / 8) of the returned mmap data and then AND the result with 8 +(1 << (3 % 8)) to see if anything is attached to that event. + +A byte-wise index check is performed as follows:: + + int index, mask; + char *status_page; + + index = status_bit / 8; + mask = 1 << (status_bit % 8); + + ... + + if (status_page[index] & mask) { + /* Enabled */ + } + +A long-wise index check is performed as follows:: + + #include <asm/bitsperlong.h> + #include <endian.h> + + #if __BITS_PER_LONG == 64 + #define endian_swap(x) htole64(x) + #else + #define endian_swap(x) htole32(x) + #endif + + long index, mask, *status_page; + + index = status_bit / __BITS_PER_LONG; + mask = 1L << (status_bit % __BITS_PER_LONG); + mask = endian_swap(mask); + + ... + + if (status_page[index] & mask) { + /* Enabled */ + } + +Administrators can easily check the status of all registered events by reading +the user_events_status file directly via a terminal. The output is as follows:: + + Byte:Name [# Comments] + ... + + Active: ActiveCount + Busy: BusyCount + Max: MaxCount + +For example, on a system that has a single event the output looks like this:: + + 1:test + + Active: 1 + Busy: 0 + Max: 32768 + +If a user enables the user event via ftrace, the output would change to this:: + + 1:test # Used by ftrace + + Active: 1 + Busy: 1 + Max: 32768 + +**NOTE:** *A status bit of 0 will never be returned. This allows user programs +to have a bit that can be used on error cases.* + +Writing Data +------------ +After registering an event the same fd that was used to register can be used +to write an entry for that event. The write_index returned must be at the start +of the data, then the remaining data is treated as the payload of the event. + +For example, if write_index returned was 1 and I wanted to write out an int +payload of the event. Then the data would have to be 8 bytes (2 ints) in size, +with the first 4 bytes being equal to 1 and the last 4 bytes being equal to the +value I want as the payload. + +In memory this would look like this:: + + int index; + int payload; + +User programs might have well known structs that they wish to use to emit out +as payloads. In those cases writev() can be used, with the first vector being +the index and the following vector(s) being the actual event payload. + +For example, if I have a struct like this:: + + struct payload { + int src; + int dst; + int flags; + }; + +It's advised for user programs to do the following:: + + struct iovec io[2]; + struct payload e; + + io[0].iov_base = &write_index; + io[0].iov_len = sizeof(write_index); + io[1].iov_base = &e; + io[1].iov_len = sizeof(e); + + writev(fd, (const struct iovec*)io, 2); + +**NOTE:** *The write_index is not emitted out into the trace being recorded.* + +Example Code +------------ +See sample code in samples/user_events. |