netdev - [PATCH v2 bpf 0/2] Fix BTF verification of enum members with a selftest

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Message-Id: <1583825550-18606-1-git-send-email-komachi.yoshiki@gmail.com>
Date:   Tue, 10 Mar 2020 16:32:28 +0900
From:   Yoshiki Komachi <komachi.yoshiki@...il.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>
Cc:     Yoshiki Komachi <komachi.yoshiki@...il.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH v2 bpf 0/2] Fix BTF verification of enum members with a selftest

btf_enum_check_member() checked if the size of "enum" as a struct
member exceeded struct_size or not. Then, the function compared it
with the size of "int". Although the size of "enum" is 4-byte by
default (i.e., equivalent to "int"), the packing feature enables
us to reduce it, as illustrated by the following example:

struct A {
        char m;
        enum { E0, E1 } __attribute__((packed)) n;
};

With such a setup above, the bpf loader gave an error attempting
to load it:

------------------------------------------------------------------
...

[3] ENUM (anon) size=1 vlen=2
        E0 val=0
        E1 val=1
[4] STRUCT A size=2 vlen=2
        m type_id=2 bits_offset=0
        n type_id=3 bits_offset=8

[4] STRUCT A size=2 vlen=2
        n type_id=3 bits_offset=8 Member exceeds struct_size

libbpf: Error loading .BTF into kernel: -22.

------------------------------------------------------------------

The related issue was previously fixed by the commit 9eea98497951 ("bpf:
fix BTF verification of enums"). On the other hand, this series fixes
this issue as well, and adds a selftest program for it.

Changes in v2:
- change an example in commit message based on Andrii's review
- add a selftest program for packed "enum" type members in struct/union

Yoshiki Komachi (2):
  bpf/btf: Fix BTF verification of enum members in struct/union
  selftests/bpf: Add test for the packed enum member in struct/union

 kernel/bpf/btf.c                       |  2 +-
 tools/testing/selftests/bpf/test_btf.c | 42 ++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

-- 
1.8.3.1