85bd316d08
Small improvements to the documentation based on Sphinx HTML doc output. Fixes:14b8f0bbe5("doc: add BPF library guide") Fixes:b901d92836("bpf: support packet data load instructions") Cc: stable@dpdk.org Signed-off-by: Harry van Haaren <harry.van.haaren@intel.com> Acked-by: Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>
67 lines
2.5 KiB
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67 lines
2.5 KiB
ReStructuredText
.. SPDX-License-Identifier: BSD-3-Clause
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Copyright(c) 2018 Intel Corporation.
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Berkeley Packet Filter Library
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==============================
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The DPDK provides an BPF library that gives the ability
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to load and execute Enhanced Berkeley Packet Filter (eBPF) bytecode within
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user-space dpdk application.
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It supports basic set of features from eBPF spec.
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Please refer to the
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`eBPF spec <https://www.kernel.org/doc/Documentation/networking/filter.txt>`_
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for more information.
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Also it introduces basic framework to load/unload BPF-based filters
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on eth devices (right now only via SW RX/TX callbacks).
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The library API provides the following basic operations:
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* Create a new BPF execution context and load user provided eBPF code into it.
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* Destroy an BPF execution context and its runtime structures and free the associated memory.
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* Execute eBPF bytecode associated with provided input parameter.
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* Provide information about natively compiled code for given BPF context.
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* Load BPF program from the ELF file and install callback to execute it on given ethdev port/queue.
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Packet data load instructions
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-----------------------------
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DPDK supports two non-generic instructions: ``(BPF_ABS | size | BPF_LD)``
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and ``(BPF_IND | size | BPF_LD)`` which are used to access packet data.
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These instructions can only be used when execution context is a pointer to
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``struct rte_mbuf`` and have seven implicit operands.
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Register ``R6`` is an implicit input that must contain pointer to ``rte_mbuf``.
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Register ``R0`` is an implicit output which contains the data fetched from the
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packet. Registers ``R1-R5`` are scratch registers
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and must not be used to store the data across these instructions.
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These instructions have implicit program exit condition as well. When
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eBPF program is trying to access the data beyond the packet boundary,
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the interpreter will abort the execution of the program. JIT compilers
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therefore must preserve this property. ``src_reg`` and ``imm32`` fields are
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explicit inputs to these instructions.
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For example, ``(BPF_IND | BPF_W | BPF_LD)`` means:
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.. code-block:: c
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uint32_t tmp;
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R0 = rte_pktmbuf_read((const struct rte_mbuf *)R6, src_reg + imm32, sizeof(tmp), &tmp);
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if (R0 == NULL)
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return FAILED;
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R0 = ntohl(*(uint32_t *)R0);
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and ``R1-R5`` were scratched.
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Not currently supported eBPF features
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-------------------------------------
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- JIT support only available for X86_64 and arm64 platforms
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- cBPF
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- tail-pointer call
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- eBPF MAP
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- external function calls for 32-bit platforms
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