linux-kernel - Re: [PATCH 3/3] objtool: check: Handle calling non-function symbols in other sections

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Date:   Mon, 21 Sep 2020 10:56:05 +0100
From:   Julien Thierry <jthierry@...hat.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, mbenes@...e.cz
Subject: Re: [PATCH 3/3] objtool: check: Handle calling non-function symbols
 in other sections

On 9/18/20 9:07 PM, Josh Poimboeuf wrote:
> On Tue, Sep 15, 2020 at 08:53:18AM +0100, Julien Thierry wrote:
>> Relocation for a call destination could point to a symbol that has
>> type STT_NOTYPE.
> 
> Then shouldn't the callee be changed to STT_FUNC?
> 

Not if it's a code symbol that does not follow standard calling convention.

It's really the same case as the !reloc, except this time it's in a 
different .text section. In arm64 there are different sections that are 
used (.text for basic code, .idmap.text for code mapped in a manner 
where virtual address == physical address, .hyp.text for kvm priviledged 
code, .tramp.text for trampolines...). There aren't many cases, but some 
symbols reference symbols in other sections, but the symbol being called 
isn't a proper function.

-- 
Julien Thierry