linux-kernel - Re: [RFC PATCH 1/2] x86/relocs: Improve diagnostic for rejected absolute references

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Message-ID: <Z7m8-4X0DnPVn-SZ@gmail.com>
Date: Sat, 22 Feb 2025 13:03:07 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Tom Lendacky <thomas.lendacky@....com>,
	Nathan Chancellor <nathan@...nel.org>
Subject: Re: [RFC PATCH 1/2] x86/relocs: Improve diagnostic for rejected
 absolute references


* Ingo Molnar <mingo@...nel.org> wrote:

> So after another 2 weeks there's been no new upstream regressions I'm 
> aware of, so - knock on wood - it seems we can leave the die() in 
> place?
> 
> But could we perhaps make it more debuggable, should it trigger - 
> such as not removing the relevant object file and improving the 
> message? I.e. make the build failure experience Linus had somewhat 
> more palatable...

For example, the new message is far better, even when combined with a 
die() build failure:

-                       die("Absolute reference to symbol '%s' not permitted in .head.text\n",
-                           symname);
-                       break;
+                       fprintf(stderr,
+                               "Absolute reference to symbol '%s+0x%lx' detected in .head.text (0x%lx).\n"
+                               "This kernel might not boot.\n",
+                               symname, rel->r_addend, offset);

as it points out that the underlying bug might result in an unbootable 
kernel image. So the user at least knows what the pain is about ...

Thanks,

	Ingo