f52c894734
Stanislav Fomichev says:
====================
Apparently, only a small subset of cgroup hooks actually falls
back to cgroup_base_func_proto. This leads to unexpected result
where not all cgroup helpers have bpf_{g,s}et_retval.
It's getting harder and harder to manage which helpers are exported
to which hooks. We now have the following call chains:
- cg_skb_func_proto
- sk_filter_func_proto
- bpf_sk_base_func_proto
- bpf_base_func_proto
So by looking at cg_skb_func_proto it's pretty hard to understand
what's going on.
For cgroup helpers, I'm proposing we do the following instead:
func_proto = cgroup_common_func_proto();
if (func_proto) return func_proto;
/* optional, if hook has 'current' */
func_proto = cgroup_current_func_proto();
if (func_proto) return func_proto;
...
switch (func_id) {
/* hook specific helpers */
case BPF_FUNC_hook_specific_helper:
return &xyz;
default:
/* always fall back to plain bpf_base_func_proto */
bpf_base_func_proto(func_id);
}
If this turns out more workable, we can follow up with converting
the rest to the same pattern.
v5:
- remove net/cls_cgroup.h include from patch 1/5 (Martin)
- move endif changes from patch 1/5 to 3/5 (Martin)
- don't define __weak protos, the ones in core.c suffice (Martin)
v4:
- don't touch existing helper.c helpers (Martin)
- drop unneeded CONFIG_CGROUP_BPF in bpf_lsm_func_proto (Martin)
v3:
- expose strtol/strtoul everywhere (Martin)
- move helpers declarations from bpf.h to bpf-cgroup.h (Martin)
- revise bpf_{g,s}et_retval documentation (Martin)
- don't expose bpf_{g,s}et_retval to cg_skb hooks (Martin)
v2:
- move everything into kernel/bpf/cgroup.c instead (Martin)
- use cgroup_common_func_proto in lsm (Martin)
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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README
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.