linux-kernel - Re: [PATCH v2] x86/EISA: Use memremap() to probe for the EISA BIOS signature

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Message-ID: <alpine.DEB.2.21.2408281109550.33652@angie.orcam.me.uk>
Date: Wed, 28 Aug 2024 11:35:02 +0100 (BST)
From: "Maciej W. Rozycki" <macro@...am.me.uk>
To: Christoph Hellwig <hch@...radead.org>
cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
    Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
    x86@...nel.org, Boris Ostrovsky <boris.ostrovsky@...cle.com>, 
    "H. Peter Anvin" <hpa@...or.com>, 
    "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, 
    Rick Edgecombe <rick.p.edgecombe@...el.com>, 
    Isaku Yamahata <isaku.yamahata@...el.com>, 
    Kevin Loughlin <kevinloughlin@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86/EISA: Use memremap() to probe for the EISA BIOS
 signature

On Wed, 28 Aug 2024, Christoph Hellwig wrote:

> > +	if (p && *p == 'E' + ('I' << 8) + ('S' << 16) + ('A' << 24))
> 
> Should this simply use strcmp now?

 It's not an ASCIIZ string, so I guess memcmp() instead.  I can see there 
is still no clarity as to whether memremap() is enough here (though it 
escapes me why it wouldn't, given that early_memremap() analogously works 
for the MP-table with the scenarios in question), so I'll let things 
settle and look into an update once I'm back from my holiday next week.

 NB sparse chokes on some headers' contents here, so it seems I can't 
really make use of it without figuring out what's wrong first.

  Maciej