[PATCH 4/5] bpf, docs: move handling of maps to Documentation/bpf/maps.rst
From: Christoph Hellwig <hch@lst.de>
Date: 2021-11-19 16:32:36
Also in:
bpf, linux-doc
Subsystem:
bpf [general] (safe dynamic programs and tools), documentation, networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Jonathan Corbet, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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> --- Documentation/bpf/maps.rst | 43 ++++++++++++++++++++++++++ Documentation/networking/filter.rst | 47 ++--------------------------- 2 files changed, 46 insertions(+), 44 deletions(-)
diff --git a/Documentation/bpf/maps.rst b/Documentation/bpf/maps.rst
index 2084b0e7cde88..f41619e312ace 100644
--- a/Documentation/bpf/maps.rst
+++ b/Documentation/bpf/maps.rst@@ -1,4 +1,47 @@ + +========= +eBPF maps ========= + +'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 + Map Types =========
diff --git a/Documentation/networking/filter.rst b/Documentation/networking/filter.rst
index 83ffcaa5b91aa..43ef05b91f986 100644
--- a/Documentation/networking/filter.rst
+++ b/Documentation/networking/filter.rst@@ -1232,9 +1232,9 @@ pointer type. The types of pointers describe their base, as follows: Pointer to the value stored in a map element. PTR_TO_MAP_VALUE_OR_NULL Either a pointer to a map value, or NULL; map accesses - (see section 'eBPF maps', below) return this type, - which becomes a PTR_TO_MAP_VALUE when checked != NULL. - Arithmetic on these pointers is forbidden. + (see maps.rst) return this type, which becomes a + a PTR_TO_MAP_VALUE when checked != NULL. Arithmetic on + these pointers is forbidden. PTR_TO_STACK Frame pointer. PTR_TO_PACKET
@@ -1402,47 +1402,6 @@ using normal C code as:: which makes such programs easier to write comparing to LD_ABS insn and significantly faster. -eBPF maps ---------- -'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 - Pruning ------- The verifier does not actually walk all possible paths through the program. For
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2.30.2