Re: [PATCH v5 0/3] Use BTF to trim return values

On Wed, Sep 2, 2026 at 10:55 PM Masami Hiramatsu [off-list ref] wrote:

On Wed, 2 Sep 2026 11:25:29 +0800
Peng Donglin [off-list ref] wrote:

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   - Do not print a return value for functions with a void return type.
   - Trim integer, enum, struct, and union values to the available return
     value width when the BTF type provides suitable size information.
   - Format integer, enum, and boolean values according to their BTF
     encoding.
   - Mark values as "(trunc)" when the return type is wider than the
     value captured by the function graph tracer.

Hmm, I really don't like the "(trunc)" If it's the real return type, then
it should just print what the real size is. No need to state it was truncated.

Thanks, I agree. We can remove the "(trunc)" suffix and print the actual
type information instead, for example:

     ret=0x5[struct:0x10]

This would indicate that the return type is a struct with a size of 0x10
bytes.

Hmm, shouldn't both the actually applied size and the true size be displayed?
e.g.

ret=0x5 (in 8 bytes, true size: 16 bytes)

Thanks, this is a good suggestion. To keep the trace concise, would this work?

  ret=0x5 (8/16B)

The suffix shows captured size and true BTF size, only when they differ.
WDYT?

Thank you,

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Would this be acceptable?

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--
Masami Hiramatsu (Google) [off-list ref]