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acrn-kernel/Documentation/bpf/maps.rst

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bpf, docs: Move handling of maps to Documentation/bpf/maps.rst Move the general maps documentation into the maps.rst file from the overall networking filter documentation and add a link instead. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-5-hch@lst.de
2021-11-20 00:32:14 +08:00
=========
eBPF maps
bpf, docs: Fix ordering of bpf documentation This commit fixes the display of the BPF documentation in the sidebar when rendered as HTML. Before this patch, the sidebar would render as follows for some sections: | BPF Documentation |- BPF Type Format (BTF) |- BPF Type Format (BTF) This was due to creating a heading in index.rst followed by a sphinx toctree, where the file referenced carries the same title as the section heading. To fix this I applied a pattern that has been established in other subfolders of Documentation: 1. Re-wrote index.rst to have a single toctree 2. Split the sections out in to their own files Additionally maps.rst and programs.rst make use of a glob pattern to include map_* or prog_* rst files in their toctree, meaning future map or program type documentation will be automatically included. Signed-off-by: Dave Tucker <dave@dtucker.co.uk> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/1a1eed800e7b9dc13b458de113a489641519b0cc.1636749493.git.dave@dtucker.co.uk
2021-11-13 05:17:24 +08:00
=========
bpf, docs: Move handling of maps to Documentation/bpf/maps.rst Move the general maps documentation into the maps.rst file from the overall networking filter documentation and add a link instead. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20211119163215.971383-5-hch@lst.de
2021-11-20 00:32:14 +08:00
'maps' is a generic storage of different types for sharing data between kernel
and userspace.
The maps are accessed from user space via BPF syscall, which has commands:
- create a map with given type and attributes
``map_fd = bpf(BPF_MAP_CREATE, union bpf_attr *attr, u32 size)``
using attr->map_type, attr->key_size, attr->value_size, attr->max_entries
returns process-local file descriptor or negative error
- lookup key in a given map
``err = bpf(BPF_MAP_LOOKUP_ELEM, union bpf_attr *attr, u32 size)``
using attr->map_fd, attr->key, attr->value
returns zero and stores found elem into value or negative error
- create or update key/value pair in a given map
``err = bpf(BPF_MAP_UPDATE_ELEM, union bpf_attr *attr, u32 size)``
using attr->map_fd, attr->key, attr->value
returns zero or negative error
- find and delete element by key in a given map
``err = bpf(BPF_MAP_DELETE_ELEM, union bpf_attr *attr, u32 size)``
using attr->map_fd, attr->key
- to delete map: close(fd)
Exiting process will delete maps automatically
userspace programs use this syscall to create/access maps that eBPF programs
are concurrently updating.
maps can have different types: hash, array, bloom filter, radix-tree, etc.
The map is defined by:
- type
- max number of elements
- key size in bytes
- value size in bytes
bpf, docs: Fix ordering of bpf documentation This commit fixes the display of the BPF documentation in the sidebar when rendered as HTML. Before this patch, the sidebar would render as follows for some sections: | BPF Documentation |- BPF Type Format (BTF) |- BPF Type Format (BTF) This was due to creating a heading in index.rst followed by a sphinx toctree, where the file referenced carries the same title as the section heading. To fix this I applied a pattern that has been established in other subfolders of Documentation: 1. Re-wrote index.rst to have a single toctree 2. Split the sections out in to their own files Additionally maps.rst and programs.rst make use of a glob pattern to include map_* or prog_* rst files in their toctree, meaning future map or program type documentation will be automatically included. Signed-off-by: Dave Tucker <dave@dtucker.co.uk> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/bpf/1a1eed800e7b9dc13b458de113a489641519b0cc.1636749493.git.dave@dtucker.co.uk
2021-11-13 05:17:24 +08:00
Map Types
=========
.. toctree::
:maxdepth: 1
:glob:
map_*