From: Yonghong Song <y...@fb.com>
Date: Thu, 22 Jun 2017 15:07:39 -0700
> Commit 31fd85816dbe ("bpf: permits narrower load from bpf program
> context fields") permits narrower load for certain ctx fields.
> The commit however will already generate a masking even if
> the prog-specific ctx conversion produces the result with
> narrower size.
>
> For example, for __sk_buff->protocol, the ctx conversion
> loads the data into register with 2-byte load.
> A narrower 2-byte load should not generate masking.
> For __sk_buff->vlan_present, the conversion function
> set the result as either 0 or 1, essentially a byte.
> The narrower 2-byte or 1-byte load should not generate masking.
>
> To avoid unnecessary masking, prog-specific *_is_valid_access
> now passes converted_op_size back to verifier, which indicates
> the valid data width after perceived future conversion.
> Based on this information, verifier is able to avoid
> unnecessary marking.
>
> Since we want more information back from prog-specific
> *_is_valid_access checking, all of them are packed into
> one data structure for more clarity.
>
> Acked-by: Daniel Borkmann <dan...@iogearbox.net>
> Signed-off-by: Yonghong Song <y...@fb.com>
Applied, thank you.
