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0ed5f79987
Eduard Zingerman says:
====================
bpf: allow void* cast using bpf_rdonly_cast()
Currently, pointers returned by `bpf_rdonly_cast()` have a type of
"pointer to btf id", and only casts to structure types are allowed.
Access to memory pointed to by these pointers is done through
`BPF_PROBE_{MEM,MEMSX}` instructions and does not produce errors on
invalid memory access.
This patch set extends `bpf_rdonly_cast()` to allow casts to an
equivalent of 'void *', effectively replacing
`bpf_probe_read_kernel()` calls in situations where access to
individual bytes or integers is necessary.
The mechanism was suggested and explored by Andrii Nakryiko in [1].
To help with detecting support for this feature, an
`enum bpf_features` is added with intended usage as follows:
if (bpf_core_enum_value_exists(enum bpf_features,
BPF_FEAT_RDONLY_CAST_TO_VOID))
...
[1] https://github.com/anakryiko/linux/tree/bpf-mem-cast
Changelog:
v2: https://lore.kernel.org/bpf/20250625000520.2700423-1-eddyz87@gmail.com/
v2 -> v3:
- dropped direct numbering for __MAX_BPF_FEAT.
v1: https://lore.kernel.org/bpf/20250624191009.902874-1-eddyz87@gmail.com/
v1 -> v2:
- renamed BPF_FEAT_TOTAL to __MAX_BPF_FEAT and moved patch introducing
bpf_features enum to the start of the series (Alexei);
- dropped patch #3 allowing optout from CAP_SYS_ADMIN drop in
prog_tests/verifier.c, use a separate runner in prog_tests/*
instead.
====================
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://patch.msgid.link/20250625182414.30659-1-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.