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")
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
btf_encoder.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/btf_encoder.c b/btf_encoder.c
index 65f6e71..1aa0ad0 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -394,7 +394,7 @@ static int32_t btf_encoder__add_base_type(struct btf_encoder *encoder, const str
* these non-regular int types to avoid libbpf/kernel complaints.
*/
byte_sz = BITS_ROUNDUP_BYTES(bt->bit_size);
- if (!byte_sz || (byte_sz & (byte_sz - 1))) {
+ if (!byte_sz || (byte_sz & (byte_sz - 1)) || byte_sz > 16) {
name = "__SANITIZED_FAKE_INT__";
byte_sz = 4;
}
--
2.34.1
