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authorLinus Torvalds <torvalds@linux-foundation.org>2022-10-04 13:38:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-10-04 13:38:03 -0700
commit0326074ff4652329f2a1a9c8685104576bd8d131 (patch)
tree9a7574c7ccb05bf4c7cb34fc5a65457bb8f495cb /Documentation/bpf
parent522667b24f08009591c90e75bfe2ffb67f555498 (diff)
parent681bf011b9b5989c6e9db6beb64494918aab9a43 (diff)
downloadlinux-0326074ff4652329f2a1a9c8685104576bd8d131.tar.gz
Merge tag 'net-next-6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next
Pull networking updates from Jakub Kicinski: "Core: - Introduce and use a single page frag cache for allocating small skb heads, clawing back the 10-20% performance regression in UDP flood test from previous fixes. - Run packets which already went thru HW coalescing thru SW GRO. This significantly improves TCP segment coalescing and simplifies deployments as different workloads benefit from HW or SW GRO. - Shrink the size of the base zero-copy send structure. - Move TCP init under a new slow / sleepable version of DO_ONCE(). BPF: - Add BPF-specific, any-context-safe memory allocator. - Add helpers/kfuncs for PKCS#7 signature verification from BPF programs. - Define a new map type and related helpers for user space -> kernel communication over a ring buffer (BPF_MAP_TYPE_USER_RINGBUF). - Allow targeting BPF iterators to loop through resources of one task/thread. - Add ability to call selected destructive functions. Expose crash_kexec() to allow BPF to trigger a kernel dump. Use CAP_SYS_BOOT check on the loading process to judge permissions. - Enable BPF to collect custom hierarchical cgroup stats efficiently by integrating with the rstat framework. - Support struct arguments for trampoline based programs. Only structs with size <= 16B and x86 are supported. - Invoke cgroup/connect{4,6} programs for unprivileged ICMP ping sockets (instead of just TCP and UDP sockets). - Add a helper for accessing CLOCK_TAI for time sensitive network related programs. - Support accessing network tunnel metadata's flags. - Make TCP SYN ACK RTO tunable by BPF programs with TCP Fast Open. - Add support for writing to Netfilter's nf_conn:mark. Protocols: - WiFi: more Extremely High Throughput (EHT) and Multi-Link Operation (MLO) work (802.11be, WiFi 7). - vsock: improve support for SO_RCVLOWAT. - SMC: support SO_REUSEPORT. - Netlink: define and document how to use netlink in a "modern" way. Support reporting missing attributes via extended ACK. - IPSec: support collect metadata mode for xfrm interfaces. - TCPv6: send consistent autoflowlabel in SYN_RECV state and RST packets. - TCP: introduce optional per-netns connection hash table to allow better isolation between namespaces (opt-in, at the cost of memory and cache pressure). - MPTCP: support TCP_FASTOPEN_CONNECT. - Add NEXT-C-SID support in Segment Routing (SRv6) End behavior. - Adjust IP_UNICAST_IF sockopt behavior for connected UDP sockets. - Open vSwitch: - Allow specifying ifindex of new interfaces. - Allow conntrack and metering in non-initial user namespace. - TLS: support the Korean ARIA-GCM crypto algorithm. - Remove DECnet support. Driver API: - Allow selecting the conduit interface used by each port in DSA switches, at runtime. - Ethernet Power Sourcing Equipment and Power Device support. - Add tc-taprio support for queueMaxSDU parameter, i.e. setting per traffic class max frame size for time-based packet schedules. - Support PHY rate matching - adapting between differing host-side and link-side speeds. - Introduce QUSGMII PHY mode and 1000BASE-KX interface mode. - Validate OF (device tree) nodes for DSA shared ports; make phylink-related properties mandatory on DSA and CPU ports. Enforcing more uniformity should allow transitioning to phylink. - Require that flash component name used during update matches one of the components for which version is reported by info_get(). - Remove "weight" argument from driver-facing NAPI API as much as possible. It's one of those magic knobs which seemed like a good idea at the time but is too indirect to use in practice. - Support offload of TLS connections with 256 bit keys. New hardware / drivers: - Ethernet: - Microchip KSZ9896 6-port Gigabit Ethernet Switch - Renesas Ethernet AVB (EtherAVB-IF) Gen4 SoCs - Analog Devices ADIN1110 and ADIN2111 industrial single pair Ethernet (10BASE-T1L) MAC+PHY. - Rockchip RV1126 Gigabit Ethernet (a version of stmmac IP). - Ethernet SFPs / modules: - RollBall / Hilink / Turris 10G copper SFPs - HALNy GPON module - WiFi: - CYW43439 SDIO chipset (brcmfmac) - CYW89459 PCIe chipset (brcmfmac) - BCM4378 on Apple platforms (brcmfmac) Drivers: - CAN: - gs_usb: HW timestamp support - Ethernet PHYs: - lan8814: cable diagnostics - Ethernet NICs: - Intel (100G): - implement control of FCS/CRC stripping - port splitting via devlink - L2TPv3 filtering offload - nVidia/Mellanox: - tunnel offload for sub-functions - MACSec offload, w/ Extended packet number and replay window offload - significantly restructure, and optimize the AF_XDP support, align the behavior with other vendors - Huawei: - configuring DSCP map for traffic class selection - querying standard FEC statistics - querying SerDes lane number via ethtool - Marvell/Cavium: - egress priority flow control - MACSec offload - AMD/SolarFlare: - PTP over IPv6 and raw Ethernet - small / embedded: - ax88772: convert to phylink (to support SFP cages) - altera: tse: convert to phylink - ftgmac100: support fixed link - enetc: standard Ethtool counters - macb: ZynqMP SGMII dynamic configuration support - tsnep: support multi-queue and use page pool - lan743x: Rx IP & TCP checksum offload - igc: add xdp frags support to ndo_xdp_xmit - Ethernet high-speed switches: - Marvell (prestera): - support SPAN port features (traffic mirroring) - nexthop object offloading - Microchip (sparx5): - multicast forwarding offload - QoS queuing offload (tc-mqprio, tc-tbf, tc-ets) - Ethernet embedded switches: - Marvell (mv88e6xxx): - support RGMII cmode - NXP (felix): - standardized ethtool counters - Microchip (lan966x): - QoS queuing offload (tc-mqprio, tc-tbf, tc-cbs, tc-ets) - traffic policing and mirroring - link aggregation / bonding offload - QUSGMII PHY mode support - Qualcomm 802.11ax WiFi (ath11k): - cold boot calibration support on WCN6750 - support to connect to a non-transmit MBSSID AP profile - enable remain-on-channel support on WCN6750 - Wake-on-WLAN support for WCN6750 - support to provide transmit power from firmware via nl80211 - support to get power save duration for each client - spectral scan support for 160 MHz - MediaTek WiFi (mt76): - WiFi-to-Ethernet bridging offload for MT7986 chips - RealTek WiFi (rtw89): - P2P support" * tag 'net-next-6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1864 commits) eth: pse: add missing static inlines once: rename _SLOW to _SLEEPABLE net: pse-pd: add regulator based PSE driver dt-bindings: net: pse-dt: add bindings for regulator based PoDL PSE controller ethtool: add interface to interact with Ethernet Power Equipment net: mdiobus: search for PSE nodes by parsing PHY nodes. net: mdiobus: fwnode_mdiobus_register_phy() rework error handling net: add framework to support Ethernet PSE and PDs devices dt-bindings: net: phy: add PoDL PSE property net: marvell: prestera: Propagate nh state from hw to kernel net: marvell: prestera: Add neighbour cache accounting net: marvell: prestera: add stub handler neighbour events net: marvell: prestera: Add heplers to interact with fib_notifier_info net: marvell: prestera: Add length macros for prestera_ip_addr net: marvell: prestera: add delayed wq and flush wq on deinit net: marvell: prestera: Add strict cleanup of fib arbiter net: marvell: prestera: Add cleanup of allocated fib_nodes net: marvell: prestera: Add router nexthops ABI eth: octeon: fix build after netif_napi_add() changes net/mlx5: E-Switch, Return EBUSY if can't get mode lock ...
Diffstat (limited to 'Documentation/bpf')
-rw-r--r--Documentation/bpf/clang-notes.rst30
-rw-r--r--Documentation/bpf/index.rst2
-rw-r--r--Documentation/bpf/instruction-set.rst316
-rw-r--r--Documentation/bpf/kfuncs.rst39
-rw-r--r--Documentation/bpf/linux-notes.rst53
5 files changed, 255 insertions, 185 deletions
diff --git a/Documentation/bpf/clang-notes.rst b/Documentation/bpf/clang-notes.rst
new file mode 100644
index 00000000000000..528feddf2db90a
--- /dev/null
+++ b/Documentation/bpf/clang-notes.rst
@@ -0,0 +1,30 @@
+.. contents::
+.. sectnum::
+
+==========================
+Clang implementation notes
+==========================
+
+This document provides more details specific to the Clang/LLVM implementation of the eBPF instruction set.
+
+Versions
+========
+
+Clang defined "CPU" versions, where a CPU version of 3 corresponds to the current eBPF ISA.
+
+Clang can select the eBPF ISA version using ``-mcpu=v3`` for example to select version 3.
+
+Arithmetic instructions
+=======================
+
+For CPU versions prior to 3, Clang v7.0 and later can enable ``BPF_ALU`` support with
+``-Xclang -target-feature -Xclang +alu32``. In CPU version 3, support is automatically included.
+
+Atomic operations
+=================
+
+Clang can generate atomic instructions by default when ``-mcpu=v3`` is
+enabled. If a lower version for ``-mcpu`` is set, the only atomic instruction
+Clang can generate is ``BPF_ADD`` *without* ``BPF_FETCH``. If you need to enable
+the atomics features, while keeping a lower ``-mcpu`` version, you can use
+``-Xclang -target-feature -Xclang +alu32``.
diff --git a/Documentation/bpf/index.rst b/Documentation/bpf/index.rst
index 1bc2c5c58bdbdc..1b50de1983ee2c 100644
--- a/Documentation/bpf/index.rst
+++ b/Documentation/bpf/index.rst
@@ -26,6 +26,8 @@ that goes into great technical depth about the BPF Architecture.
classic_vs_extended.rst
bpf_licensing
test_debug
+ clang-notes
+ linux-notes
other
.. only:: subproject and html
diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
index 0ac7ae40be37c7..5d798437dad47f 100644
--- a/Documentation/bpf/instruction-set.rst
+++ b/Documentation/bpf/instruction-set.rst
@@ -1,7 +1,12 @@
+.. contents::
+.. sectnum::
+
+========================================
+eBPF Instruction Set Specification, v1.0
+========================================
+
+This document specifies version 1.0 of the eBPF instruction set.
-====================
-eBPF Instruction Set
-====================
Registers and calling convention
================================
@@ -11,10 +16,10 @@ all of which are 64-bits wide.
The eBPF calling convention is defined as:
- * R0: return value from function calls, and exit value for eBPF programs
- * R1 - R5: arguments for function calls
- * R6 - R9: callee saved registers that function calls will preserve
- * R10: read-only frame pointer to access stack
+* R0: return value from function calls, and exit value for eBPF programs
+* R1 - R5: arguments for function calls
+* R6 - R9: callee saved registers that function calls will preserve
+* R10: read-only frame pointer to access stack
R0 - R5 are scratch registers and eBPF programs needs to spill/fill them if
necessary across calls.
@@ -24,17 +29,17 @@ Instruction encoding
eBPF has two instruction encodings:
- * the basic instruction encoding, which uses 64 bits to encode an instruction
- * the wide instruction encoding, which appends a second 64-bit immediate value
- (imm64) after the basic instruction for a total of 128 bits.
+* the basic instruction encoding, which uses 64 bits to encode an instruction
+* the wide instruction encoding, which appends a second 64-bit immediate value
+ (imm64) after the basic instruction for a total of 128 bits.
The basic instruction encoding looks as follows:
- ============= ======= =============== ==================== ============
- 32 bits (MSB) 16 bits 4 bits 4 bits 8 bits (LSB)
- ============= ======= =============== ==================== ============
- immediate offset source register destination register opcode
- ============= ======= =============== ==================== ============
+============= ======= =============== ==================== ============
+32 bits (MSB) 16 bits 4 bits 4 bits 8 bits (LSB)
+============= ======= =============== ==================== ============
+immediate offset source register destination register opcode
+============= ======= =============== ==================== ============
Note that most instructions do not use all of the fields.
Unused fields shall be cleared to zero.
@@ -44,30 +49,30 @@ Instruction classes
The three LSB bits of the 'opcode' field store the instruction class:
- ========= ===== ===============================
- class value description
- ========= ===== ===============================
- BPF_LD 0x00 non-standard load operations
- BPF_LDX 0x01 load into register operations
- BPF_ST 0x02 store from immediate operations
- BPF_STX 0x03 store from register operations
- BPF_ALU 0x04 32-bit arithmetic operations
- BPF_JMP 0x05 64-bit jump operations
- BPF_JMP32 0x06 32-bit jump operations
- BPF_ALU64 0x07 64-bit arithmetic operations
- ========= ===== ===============================
+========= ===== =============================== ===================================
+class value description reference
+========= ===== =============================== ===================================
+BPF_LD 0x00 non-standard load operations `Load and store instructions`_
+BPF_LDX 0x01 load into register operations `Load and store instructions`_
+BPF_ST 0x02 store from immediate operations `Load and store instructions`_
+BPF_STX 0x03 store from register operations `Load and store instructions`_
+BPF_ALU 0x04 32-bit arithmetic operations `Arithmetic and jump instructions`_
+BPF_JMP 0x05 64-bit jump operations `Arithmetic and jump instructions`_
+BPF_JMP32 0x06 32-bit jump operations `Arithmetic and jump instructions`_
+BPF_ALU64 0x07 64-bit arithmetic operations `Arithmetic and jump instructions`_
+========= ===== =============================== ===================================
Arithmetic and jump instructions
================================
-For arithmetic and jump instructions (BPF_ALU, BPF_ALU64, BPF_JMP and
-BPF_JMP32), the 8-bit 'opcode' field is divided into three parts:
+For arithmetic and jump instructions (``BPF_ALU``, ``BPF_ALU64``, ``BPF_JMP`` and
+``BPF_JMP32``), the 8-bit 'opcode' field is divided into three parts:
- ============== ====== =================
- 4 bits (MSB) 1 bit 3 bits (LSB)
- ============== ====== =================
- operation code source instruction class
- ============== ====== =================
+============== ====== =================
+4 bits (MSB) 1 bit 3 bits (LSB)
+============== ====== =================
+operation code source instruction class
+============== ====== =================
The 4th bit encodes the source operand:
@@ -84,51 +89,51 @@ The four MSB bits store the operation code.
Arithmetic instructions
-----------------------
-BPF_ALU uses 32-bit wide operands while BPF_ALU64 uses 64-bit wide operands for
+``BPF_ALU`` uses 32-bit wide operands while ``BPF_ALU64`` uses 64-bit wide operands for
otherwise identical operations.
-The code field encodes the operation as below:
-
- ======== ===== =================================================
- code value description
- ======== ===== =================================================
- BPF_ADD 0x00 dst += src
- BPF_SUB 0x10 dst -= src
- BPF_MUL 0x20 dst \*= src
- BPF_DIV 0x30 dst /= src
- BPF_OR 0x40 dst \|= src
- BPF_AND 0x50 dst &= src
- BPF_LSH 0x60 dst <<= src
- BPF_RSH 0x70 dst >>= src
- BPF_NEG 0x80 dst = ~src
- BPF_MOD 0x90 dst %= src
- BPF_XOR 0xa0 dst ^= src
- BPF_MOV 0xb0 dst = src
- BPF_ARSH 0xc0 sign extending shift right
- BPF_END 0xd0 byte swap operations (see separate section below)
- ======== ===== =================================================
-
-BPF_ADD | BPF_X | BPF_ALU means::
+The 'code' field encodes the operation as below:
+
+======== ===== ==========================================================
+code value description
+======== ===== ==========================================================
+BPF_ADD 0x00 dst += src
+BPF_SUB 0x10 dst -= src
+BPF_MUL 0x20 dst \*= src
+BPF_DIV 0x30 dst /= src
+BPF_OR 0x40 dst \|= src
+BPF_AND 0x50 dst &= src
+BPF_LSH 0x60 dst <<= src
+BPF_RSH 0x70 dst >>= src
+BPF_NEG 0x80 dst = ~src
+BPF_MOD 0x90 dst %= src
+BPF_XOR 0xa0 dst ^= src
+BPF_MOV 0xb0 dst = src
+BPF_ARSH 0xc0 sign extending shift right
+BPF_END 0xd0 byte swap operations (see `Byte swap instructions`_ below)
+======== ===== ==========================================================
+
+``BPF_ADD | BPF_X | BPF_ALU`` means::
dst_reg = (u32) dst_reg + (u32) src_reg;
-BPF_ADD | BPF_X | BPF_ALU64 means::
+``BPF_ADD | BPF_X | BPF_ALU64`` means::
dst_reg = dst_reg + src_reg
-BPF_XOR | BPF_K | BPF_ALU means::
+``BPF_XOR | BPF_K | BPF_ALU`` means::
src_reg = (u32) src_reg ^ (u32) imm32
-BPF_XOR | BPF_K | BPF_ALU64 means::
+``BPF_XOR | BPF_K | BPF_ALU64`` means::
src_reg = src_reg ^ imm32
Byte swap instructions
-----------------------
+~~~~~~~~~~~~~~~~~~~~~~
The byte swap instructions use an instruction class of ``BPF_ALU`` and a 4-bit
-code field of ``BPF_END``.
+'code' field of ``BPF_END``.
The byte swap instructions operate on the destination register
only and do not use a separate source register or immediate value.
@@ -136,14 +141,14 @@ only and do not use a separate source register or immediate value.
The 1-bit source operand field in the opcode is used to select what byte
order the operation convert from or to:
- ========= ===== =================================================
- source value description
- ========= ===== =================================================
- BPF_TO_LE 0x00 convert between host byte order and little endian
- BPF_TO_BE 0x08 convert between host byte order and big endian
- ========= ===== =================================================
+========= ===== =================================================
+source value description
+========= ===== =================================================
+BPF_TO_LE 0x00 convert between host byte order and little endian
+BPF_TO_BE 0x08 convert between host byte order and big endian
+========= ===== =================================================
-The imm field encodes the width of the swap operations. The following widths
+The 'imm' field encodes the width of the swap operations. The following widths
are supported: 16, 32 and 64.
Examples:
@@ -156,35 +161,31 @@ Examples:
dst_reg = htobe64(dst_reg)
-``BPF_FROM_LE`` and ``BPF_FROM_BE`` exist as aliases for ``BPF_TO_LE`` and
-``BPF_TO_BE`` respectively.
-
-
Jump instructions
-----------------
-BPF_JMP32 uses 32-bit wide operands while BPF_JMP uses 64-bit wide operands for
+``BPF_JMP32`` uses 32-bit wide operands while ``BPF_JMP`` uses 64-bit wide operands for
otherwise identical operations.
-The code field encodes the operation as below:
-
- ======== ===== ========================= ============
- code value description notes
- ======== ===== ========================= ============
- BPF_JA 0x00 PC += off BPF_JMP only
- BPF_JEQ 0x10 PC += off if dst == src
- BPF_JGT 0x20 PC += off if dst > src unsigned
- BPF_JGE 0x30 PC += off if dst >= src unsigned
- BPF_JSET 0x40 PC += off if dst & src
- BPF_JNE 0x50 PC += off if dst != src
- BPF_JSGT 0x60 PC += off if dst > src signed
- BPF_JSGE 0x70 PC += off if dst >= src signed
- BPF_CALL 0x80 function call
- BPF_EXIT 0x90 function / program return BPF_JMP only
- BPF_JLT 0xa0 PC += off if dst < src unsigned
- BPF_JLE 0xb0 PC += off if dst <= src unsigned
- BPF_JSLT 0xc0 PC += off if dst < src signed
- BPF_JSLE 0xd0 PC += off if dst <= src signed
- ======== ===== ========================= ============
+The 'code' field encodes the operation as below:
+
+======== ===== ========================= ============
+code value description notes
+======== ===== ========================= ============
+BPF_JA 0x00 PC += off BPF_JMP only
+BPF_JEQ 0x10 PC += off if dst == src
+BPF_JGT 0x20 PC += off if dst > src unsigned
+BPF_JGE 0x30 PC += off if dst >= src unsigned
+BPF_JSET 0x40 PC += off if dst & src
+BPF_JNE 0x50 PC += off if dst != src
+BPF_JSGT 0x60 PC += off if dst > src signed
+BPF_JSGE 0x70 PC += off if dst >= src signed
+BPF_CALL 0x80 function call
+BPF_EXIT 0x90 function / program return BPF_JMP only
+BPF_JLT 0xa0 PC += off if dst < src unsigned
+BPF_JLE 0xb0 PC += off if dst <= src unsigned
+BPF_JSLT 0xc0 PC += off if dst < src signed
+BPF_JSLE 0xd0 PC += off if dst <= src signed
+======== ===== ========================= ============
The eBPF program needs to store the return value into register R0 before doing a
BPF_EXIT.
@@ -193,14 +194,26 @@ BPF_EXIT.
Load and store instructions
===========================
-For load and store instructions (BPF_LD, BPF_LDX, BPF_ST and BPF_STX), the
+For load and store instructions (``BPF_LD``, ``BPF_LDX``, ``BPF_ST``, and ``BPF_STX``), the
8-bit 'opcode' field is divided as:
- ============ ====== =================
- 3 bits (MSB) 2 bits 3 bits (LSB)
- ============ ====== =================
- mode size instruction class
- ============ ====== =================
+============ ====== =================
+3 bits (MSB) 2 bits 3 bits (LSB)
+============ ====== =================
+mode size instruction class
+============ ====== =================
+
+The mode modifier is one of:
+
+ ============= ===== ==================================== =============
+ mode modifier value description reference
+ ============= ===== ==================================== =============
+ BPF_IMM 0x00 64-bit immediate instructions `64-bit immediate instructions`_
+ BPF_ABS 0x20 legacy BPF packet access (absolute) `Legacy BPF Packet access instructions`_
+ BPF_IND 0x40 legacy BPF packet access (indirect) `Legacy BPF Packet access instructions`_
+ BPF_MEM 0x60 regular load and store operations `Regular load and store operations`_
+ BPF_ATOMIC 0xc0 atomic operations `Atomic operations`_
+ ============= ===== ==================================== =============
The size modifier is one of:
@@ -213,19 +226,6 @@ The size modifier is one of:
BPF_DW 0x18 double word (8 bytes)
============= ===== =====================
-The mode modifier is one of:
-
- ============= ===== ====================================
- mode modifier value description
- ============= ===== ====================================
- BPF_IMM 0x00 64-bit immediate instructions
- BPF_ABS 0x20 legacy BPF packet access (absolute)
- BPF_IND 0x40 legacy BPF packet access (indirect)
- BPF_MEM 0x60 regular load and store operations
- BPF_ATOMIC 0xc0 atomic operations
- ============= ===== ====================================
-
-
Regular load and store operations
---------------------------------
@@ -256,44 +256,42 @@ by other eBPF programs or means outside of this specification.
All atomic operations supported by eBPF are encoded as store operations
that use the ``BPF_ATOMIC`` mode modifier as follows:
- * ``BPF_ATOMIC | BPF_W | BPF_STX`` for 32-bit operations
- * ``BPF_ATOMIC | BPF_DW | BPF_STX`` for 64-bit operations
- * 8-bit and 16-bit wide atomic operations are not supported.
+* ``BPF_ATOMIC | BPF_W | BPF_STX`` for 32-bit operations
+* ``BPF_ATOMIC | BPF_DW | BPF_STX`` for 64-bit operations
+* 8-bit and 16-bit wide atomic operations are not supported.
-The imm field is used to encode the actual atomic operation.
+The 'imm' field is used to encode the actual atomic operation.
Simple atomic operation use a subset of the values defined to encode
-arithmetic operations in the imm field to encode the atomic operation:
+arithmetic operations in the 'imm' field to encode the atomic operation:
- ======== ===== ===========
- imm value description
- ======== ===== ===========
- BPF_ADD 0x00 atomic add
- BPF_OR 0x40 atomic or
- BPF_AND 0x50 atomic and
- BPF_XOR 0xa0 atomic xor
- ======== ===== ===========
+======== ===== ===========
+imm value description
+======== ===== ===========
+BPF_ADD 0x00 atomic add
+BPF_OR 0x40 atomic or
+BPF_AND 0x50 atomic and
+BPF_XOR 0xa0 atomic xor
+======== ===== ===========
-``BPF_ATOMIC | BPF_W | BPF_STX`` with imm = BPF_ADD means::
+``BPF_ATOMIC | BPF_W | BPF_STX`` with 'imm' = BPF_ADD means::
*(u32 *)(dst_reg + off16) += src_reg
-``BPF_ATOMIC | BPF_DW | BPF_STX`` with imm = BPF ADD means::
+``BPF_ATOMIC | BPF_DW | BPF_STX`` with 'imm' = BPF ADD means::
*(u64 *)(dst_reg + off16) += src_reg
-``BPF_XADD`` is a deprecated name for ``BPF_ATOMIC | BPF_ADD``.
-
In addition to the simple atomic operations, there also is a modifier and
two complex atomic operations:
- =========== ================ ===========================
- imm value description
- =========== ================ ===========================
- BPF_FETCH 0x01 modifier: return old value
- BPF_XCHG 0xe0 | BPF_FETCH atomic exchange
- BPF_CMPXCHG 0xf0 | BPF_FETCH atomic compare and exchange
- =========== ================ ===========================
+=========== ================ ===========================
+imm value description
+=========== ================ ===========================
+BPF_FETCH 0x01 modifier: return old value
+BPF_XCHG 0xe0 | BPF_FETCH atomic exchange
+BPF_CMPXCHG 0xf0 | BPF_FETCH atomic compare and exchange
+=========== ================ ===========================
The ``BPF_FETCH`` modifier is optional for simple atomic operations, and
always set for the complex atomic operations. If the ``BPF_FETCH`` flag
@@ -309,16 +307,10 @@ The ``BPF_CMPXCHG`` operation atomically compares the value addressed by
value that was at ``dst_reg + off`` before the operation is zero-extended
and loaded back to ``R0``.
-Clang can generate atomic instructions by default when ``-mcpu=v3`` is
-enabled. If a lower version for ``-mcpu`` is set, the only atomic instruction
-Clang can generate is ``BPF_ADD`` *without* ``BPF_FETCH``. If you need to enable
-the atomics features, while keeping a lower ``-mcpu`` version, you can use
-``-Xclang -target-feature -Xclang +alu32``.
-
64-bit immediate instructions
-----------------------------
-Instructions with the ``BPF_IMM`` mode modifier use the wide instruction
+Instructions with the ``BPF_IMM`` 'mode' modifier use the wide instruction
encoding for an extra imm64 value.
There is currently only one such instruction.
@@ -331,36 +323,6 @@ There is currently only one such instruction.
Legacy BPF Packet access instructions
-------------------------------------
-eBPF has special instructions for access to packet data that have been
-carried over from classic BPF to retain the performance of legacy socket
-filters running in the eBPF interpreter.
-
-The instructions come in two forms: ``BPF_ABS | <size> | BPF_LD`` and
-``BPF_IND | <size> | BPF_LD``.
-
-These instructions are used to access packet data and can only be used when
-the program context is a pointer to networking packet. ``BPF_ABS``
-accesses packet data at an absolute offset specified by the immediate data
-and ``BPF_IND`` access packet data at an offset that includes the value of
-a register in addition to the immediate data.
-
-These instructions have seven implicit operands:
-
- * Register R6 is an implicit input that must contain pointer to a
- struct sk_buff.
- * Register R0 is an implicit output which contains the data fetched from
- the packet.
- * Registers R1-R5 are scratch registers that are clobbered after a call to
- ``BPF_ABS | BPF_LD`` or ``BPF_IND | BPF_LD`` instructions.
-
-These instructions have an implicit program exit condition as well. When an
-eBPF program is trying to access the data beyond the packet boundary, the
-program execution will be aborted.
-
-``BPF_ABS | BPF_W | BPF_LD`` means::
-
- R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + imm32))
-
-``BPF_IND | BPF_W | BPF_LD`` means::
-
- R0 = ntohl(*(u32 *) (((struct sk_buff *) R6)->data + src_reg + imm32))
+eBPF previously introduced special instructions for access to packet data that were
+carried over from classic BPF. However, these instructions are
+deprecated and should no longer be used.
diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst
index c0b7dae6dbf549..0f858156371de1 100644
--- a/Documentation/bpf/kfuncs.rst
+++ b/Documentation/bpf/kfuncs.rst
@@ -137,14 +137,37 @@ KF_ACQUIRE and KF_RET_NULL flags.
--------------------------
The KF_TRUSTED_ARGS flag is used for kfuncs taking pointer arguments. It
-indicates that the all pointer arguments will always be refcounted, and have
-their offset set to 0. It can be used to enforce that a pointer to a refcounted
-object acquired from a kfunc or BPF helper is passed as an argument to this
-kfunc without any modifications (e.g. pointer arithmetic) such that it is
-trusted and points to the original object. This flag is often used for kfuncs
-that operate (change some property, perform some operation) on an object that
-was obtained using an acquire kfunc. Such kfuncs need an unchanged pointer to
-ensure the integrity of the operation being performed on the expected object.
+indicates that the all pointer arguments will always have a guaranteed lifetime,
+and pointers to kernel objects are always passed to helpers in their unmodified
+form (as obtained from acquire kfuncs).
+
+It can be used to enforce that a pointer to a refcounted object acquired from a
+kfunc or BPF helper is passed as an argument to this kfunc without any
+modifications (e.g. pointer arithmetic) such that it is trusted and points to
+the original object.
+
+Meanwhile, it is also allowed pass pointers to normal memory to such kfuncs,
+but those can have a non-zero offset.
+
+This flag is often used for kfuncs that operate (change some property, perform
+some operation) on an object that was obtained using an acquire kfunc. Such
+kfuncs need an unchanged pointer to ensure the integrity of the operation being
+performed on the expected object.
+
+2.4.6 KF_SLEEPABLE flag
+-----------------------
+
+The KF_SLEEPABLE flag is used for kfuncs that may sleep. Such kfuncs can only
+be called by sleepable BPF programs (BPF_F_SLEEPABLE).
+
+2.4.7 KF_DESTRUCTIVE flag
+--------------------------
+
+The KF_DESTRUCTIVE flag is used to indicate functions calling which is
+destructive to the system. For example such a call can result in system
+rebooting or panicking. Due to this additional restrictions apply to these
+calls. At the moment they only require CAP_SYS_BOOT capability, but more can be
+added later.
2.5 Registering the kfuncs
--------------------------
diff --git a/Documentation/bpf/linux-notes.rst b/Documentation/bpf/linux-notes.rst
new file mode 100644
index 00000000000000..956b0c86699d07
--- /dev/null
+++ b/Documentation/bpf/linux-notes.rst
@@ -0,0 +1,53 @@
+.. contents::
+.. sectnum::
+
+==========================
+Linux implementation notes
+==========================
+
+This document provides more details specific to the Linux kernel implementation of the eBPF instruction set.
+
+Byte swap instructions
+======================
+
+``BPF_FROM_LE`` and ``BPF_FROM_BE`` exist as aliases for ``BPF_TO_LE`` and ``BPF_TO_BE`` respectively.
+
+Legacy BPF Packet access instructions
+=====================================
+
+As mentioned in the `ISA standard documentation <instruction-set.rst#legacy-bpf-packet-access-instructions>`_,
+Linux has special eBPF instructions for access to packet data that have been
+carried over from classic BPF to retain the performance of legacy socket
+filters running in the eBPF interpreter.
+
+The instructions come in two forms: ``BPF_ABS | <size> | BPF_LD`` and
+``BPF_IND | <size> | BPF_LD``.
+
+These instructions are used to access packet data and can only be used when
+the program context is a pointer to a networking packet. ``BPF_ABS``
+accesses packet data at an absolute offset specified by the immediate data
+and ``BPF_IND`` access packet data at an offset that includes the value of
+a register in addition to the immediate data.
+
+These instructions have seven implicit operands:
+
+* Register R6 is an implicit input that must contain a pointer to a
+ struct sk_buff.
+* Register R0 is an implicit output which contains the data fetched from
+ the packet.
+* Registers R1-R5 are scratch registers that are clobbered by the
+ instruction.
+
+These instructions have an implicit program exit condition as well. If an
+eBPF program attempts access data beyond the packet boundary, the
+program execution will be aborted.
+
+``BPF_ABS | BPF_W | BPF_LD`` (0x20) means::
+
+ R0 = ntohl(*(u32 *) ((struct sk_buff *) R6->data + imm))
+
+where ``ntohl()`` converts a 32-bit value from network byte order to host byte order.
+
+``BPF_IND | BPF_W | BPF_LD`` (0x40) means::
+
+ R0 = ntohl(*(u32 *) ((struct sk_buff *) R6->data + src + imm))