linux-kernel - Re: [PATCH v2 1/3] x86/boot: Introduce the kernel

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Message-ID: <c9eb5a39-ced5-b35d-616d-6ffbe15c1396@zytor.com>
Date:   Mon, 30 Sep 2019 10:18:43 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Daniel Kiper <daniel.kiper@...cle.com>
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, bp@...en8.de, corbet@....net,
        dpsmith@...rtussolutions.com, eric.snowberg@...cle.com,
        kanth.ghatraju@...cle.com, konrad.wilk@...cle.com,
        mingo@...hat.com, ross.philipson@...cle.com, tglx@...utronix.de
Subject: Re: [PATCH v2 1/3] x86/boot: Introduce the kernel_info

On 2019-09-30 08:01, Daniel Kiper wrote:
> 
> OK.
> 
>> field for the entire .kernel_info section, thus ensuring it is a
>> single self-contained blob.
> 
> .rodata.kernel_info contains its total size immediately behind the
> "InfO" header. Do you suggest that we should add the size of
> .rodata.kernel_info into setup_header too?
> 

No, what I want is a chunked architecture for kernel_info.

That is:

/* Common chunk header */
struct kernel_info_header {
	uint32_t magic;
	uint32_t len;
};

/* Top-level chunk, always first */
#define KERNEL_INFO_MAGIC 0x45fdbe4f

struct kernel_info {
	struct kernel_info_header hdr;
	uint32_t total_size;		/* Total size of all chunks */

	/* Various fixed-sized data objects, OR offsets to other chunks */
};

Also "InfO" is a pretty hideous magic. In general, all-ASCII magics have much
higher risk of collision than *RANDOM* binary numbers. However, for a chunked
architecture they do have the advantage that they can be used also as a human
name or file name for the chunk, e.,g. in sysfs, so maybe something like
"LnuX" or even "LToP" for the top-level chunk might make sense.

How does that sound?

	-hpa