btf_encoder: Fix a dwarf type DW_ATE_unsigned_1024 to btf encoding issue
Nick Desaulniers reported an issue ([1]) where an 128-byte sized type
(DW_ATE_unsigned_1024) cannot be encoded into BTF with failure message
likes below:
$ pahole -J reduced.o
[2] INT DW_ATE_unsigned_1024 Error emitting BTF type
Encountered error while encoding BTF.
See [1] for how to reproduce the issue.
The failure is due to currently BTF int type only supports upto 16
bytes (__int128) and in this case the dwarf int type is 128-byte.
The DW_ATE_unsigned_1024 is not a normal type for variable/func
declaration etc. It is used in DW_AT_location. There are two
ways to resolve this issue.
(1). If btf encoding is expected, remove all dwarf int types
where btf encoding will failure, e.g., non-power-of-2
bytes, or greater than 16 bytes.
(2). do a sanitization in btf_encoder ([2]).
This patch uses method (2) since it is a simple fix in btf_encoder.
I checked my local built vmlinux with latest
bpf-next. There is only one instance of DW_ATE_unsigned_24 (used in
DW_AT_location) so I expect irregular int types should be very rare.
[1] https://github.com/libbpf/libbpf/pull/680
[2] commit 7d8e829f636f ("btf_encoder: Sanitize non-regular int base type")
Bug: 279144929
Change-Id: Ie93d2b0cc5a232cb1853f44dbe395ad3c95210a3
Signed-off-by: Yonghong Song <yhs@fb.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Matthias Maennich <maennich@google.com>
1 file changed
