libbpf-rs: Fix BTF int offset extraction from aux word#1367
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The auxiliary u32 for BTF_KIND_INT packs several fields; the offset lives in bits 16–23 (see BTF_INT_ENCODING in the kernel UAPI). After masking with 0x00_ff_00_00, shifting by 24 decodes the wrong bit range, so Int::offset was effectively wrong. Shift by 16 to align the mask with the documented layout.
d-e-s-o
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Apr 6, 2026
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The mask 0x00_ff_00_00 must be paired with a shift of 16, not 24, so the field matches the layout used by BTF_INT_ENCODING in the kernel UAPI.
Shouldn't this be about BTF_INT_OFFSET? BTF_INT_ENCODING seems to use 24.
Looks good to me other than that. Thanks!
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Closing pull request as it is stale. |
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What
Correct the shift applied after masking bits 16–23 of the BTF
KIND_INTauxiliaryu32when buildingInt::offset. The mask0x00_ff_00_00must be paired with a shift of 16, not 24, so the field matches the layout used byBTF_INT_ENCODINGin the kernel UAPI.Why
With shift 24, the masked value was decoded from the wrong bit positions, so
Int::offsetdid not reflect the encoded offset.