Re: [PATCH 5/5] arm64: mte: Document the core dump file format

[Catalin Marinas <catalin.marinas@arm.com>]

Hi Luis,

On Mon, Jan 03, 2022 at 02:27:54PM -0300, Luis Machado wrote:
> On 12/8/21 9:19 AM, Catalin Marinas wrote:
> > diff --git a/Documentation/arm64/memory-tagging-extension.rst b/Documentation/arm64/memory-tagging-extension.rst
> > index 7b99c8f428eb..34c7eb47f61e 100644
> > --- a/Documentation/arm64/memory-tagging-extension.rst
> > +++ b/Documentation/arm64/memory-tagging-extension.rst
> > @@ -213,6 +213,28 @@ address ABI control and MTE configuration of a process as per the
> >   Documentation/arm64/tagged-address-abi.rst and above. The corresponding
> >   ``regset`` is 1 element of 8 bytes (``sizeof(long))``).
> > +Core dump support
> > +-----------------
> > +
> > +The allocation tags for user memory mapped with ``PROT_MTE`` are dumped
> > +in the core file as additional ``PT_ARM_MEMTAG_MTE`` segments. The
> > +program header for such segment is defined as:
> > +
> > +:``p_type``: ``PT_ARM_MEMTAG_MTE``
> > +:``p_flags``: 0
> > +:``p_offset``: segment file offset
> > +:``p_vaddr``: segment virtual address, same as the corresponding
> > +  ``PT_LOAD`` segment
> > +:``p_paddr``: 0
> > +:``p_filesz``: segment size in file, calculated as ``p_mem_sz / 16 / 2``
> 
> For the sake of making things extra clear, I'd describe what the constants
> (16 and 2) mean.

I'll rewrite this as: "``p_mem_sz / 32`` (two 4-bit tags cover 32 bytes
of memory)". I find the "16 / 2" more confusing.

> Acked-by: Luis Machado <luis.machado@linaro.org>

Thanks for the acks.

-- 
Catalin

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