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

Message ID 1583825550-18606-1-git-send-email-komachi.yoshiki@gmail.com
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Series Fix BTF verification of enum members with a selftest | expand

Message

Yoshiki Komachi March 10, 2020, 7:32 a.m. UTC 
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(-)