linux-kernel - Re: [PATCH v2 1/2] x86: Check return values from early

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Date:   Wed, 4 Jan 2023 12:58:48 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Ross Philipson <ross.philipson@...cle.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        dpsmith@...rtussolutions.com, tglx@...utronix.de, mingo@...hat.com,
        hpa@...or.com, luto@...capital.net, dave.hansen@...ux.intel.com,
        kanth.ghatraju@...cle.com, trenchboot-devel@...glegroups.com,
        jailhouse-dev@...glegroups.com, jan.kiszka@...mens.com,
        xen-devel@...ts.xenproject.org, jgross@...e.com,
        boris.ostrovsky@...cle.com, andrew.cooper3@...rix.com
Subject: Re: [PATCH v2 1/2] x86: Check return values from early_memremap calls

On Thu, Nov 10, 2022 at 08:07:53AM -0800, Dave Hansen wrote:
> On 11/10/22 07:45, Ross Philipson wrote:
> >  	dt = early_memremap(initial_dtb, map_len);
> > +	if (!dt) {
> > +		pr_warn("failed to memremap initial dtb\n");
> > +		return;
> > +	}
> 
> Are all of these new pr_warn/err()'s really adding much value?  They all
> look pretty generic.  It makes me wonder if we should just spit out a
> generic message in early_memremap() and save all the callers the trouble.

Well, let's see.

early_memremap() calls __early_ioremap() and that one already warns befofe each
NULL return. So I guess we don't need the error messages as we will know where
it starts failing.

I guess we still need the error handling though.

I.e., this above should be:

    dt = early_memremap(initial_dtb, map_len);
+   if (!dt)
+           return;

so that we don't go off into the weeds with a NULL ptr.

Or?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette