mirror of
https://github.com/ukui/kernel.git
synced 2026-03-09 10:07:04 -07:00
Yonghong Song
9de2640b06
For multiple dimensional arrays like below,
int a[2][3]
both llvm and pahole generated one BTF_KIND_ARRAY type like
. element_type: int
. index_type: unsigned int
. number of elements: 6
Such a collapsed BTF_KIND_ARRAY type will cause the divergence
in BTF vs. the user code. In the compile-once-run-everywhere
project, the header file is generated from BTF and used for bpf
program, and the definition in the header file will be different
from what user expects.
But the kernel actually supports chained multi-dimensional array
types properly. The above "int a[2][3]" can be represented as
Type #n:
. element_type: int
. index_type: unsigned int
. number of elements: 3
Type #(n+1):
. element_type: type #n
. index_type: unsigned int
. number of elements: 2
The following llvm commit
https://reviews.llvm.org/rL357215
also enables llvm to generated proper chained multi-dimensional arrays.
The test_btf already has a raw test ("struct test #1") for chained
multi-dimensional arrays. This patch added amended bpffs test for
chained multi-dimensional arrays.
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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 Restructured Text 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.