linux-kernel - Re: [PATCH] x86/speculation, objtool: Use absolute relocations for annotations

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Message-ID: <20230921171900.GB29413@noisy.programming.kicks-ass.net>
Date:   Thu, 21 Sep 2023 19:19:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Fangrui Song <maskray@...gle.com>
Cc:     x86@...nel.org, Josh Poimboeuf <jpoimboe@...nel.org>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] x86/speculation, objtool: Use absolute relocations for
 annotations

On Thu, Sep 21, 2023 at 09:26:43AM -0700, Fangrui Song wrote:

> I do not see why absolute things need 12 byte entries.
> We can freely use `.long .text.foo` even in ELFCLASS64 object files.
> There is no risk of overflow (the ultimate link .text.foo may have an
> address of 0xffffffff........) since the section will be discarded.

And you're sure no toolchain is going to be clever and tell me that the
absolute relocation will want to be 8 bytes and does not fit in the 4
bytes allotted?

Because clearly that is something some clever assembler is going to
complain about any day now.