Re: [Bug 292195] arm64: panic on coredump with sve instructions

Sounds like an investigation candidate for why pkg builder ampere1 crashes now and than?

Ronald.
 
Van: [email protected]
Datum: maandag, 5 januari 2026 09:39
Aan: [email protected]
Onderwerp: [Bug 292195] arm64: panic on coredump with sve instructions
> 
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=292195
> 
>             Bug ID: 292195
>            Summary: arm64: panic on coredump with sve instructions
>            Product: Base System
>            Version: 16.0-CURRENT
>           Hardware: Any
>                 OS: Any
>             Status: New
>           Severity: Affects Some People
>           Priority: ---
>          Component: arm
>           Assignee: [email protected]
>           Reporter: [email protected]
> 
> Created attachment 266838
>   --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=266838&action=edit
> vfp.c.patch
> 
> When trying to reproduce bug 292177 on 16-CURRENT I unexpectedly encountered a
> kernel panic. It looks like the panic was unique to coredumping in SVE code.
> 
> The coredump logic calls get_arm64_sve twice: once to get the note size, and
> once to get the data. The note size calculation depended on the volatile
> PCB_FP_SVEVALID flag. If this flag was cleared between the two calls (e.g., due
> to a context switch clearing the flag to comply with the ABI), the second call
> would expect a smaller buffer size than the first, triggering the KASSERT panic
> ("invalid size").
> 
> Fix this by:
> 1. Using pcb->pcb_svesaved != NULL (a stable indicator of SVE usage) to
> determine the note size.
> 2. Calling vfp_to_sve_sync() if SVE is not currently valid but SVE state is
> saved, ensuring the SVE buffer in the core dump contains the most up-to-date
> register values.
> 
> -- 
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> 
> 
>