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Message-ID: <8a4f10b1-70b3-25fe-9ffc-4f24a1531139@kernel.org>
Date:   Mon, 25 Jul 2022 07:44:08 +0200
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Subject: Re: [PATCH 5.18 13/70] objtool: skip non-text sections when adding
 return-thunk sites
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To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-kernel@vger.kernel.org
Cc:     stable@vger.kernel.org,
        Thadeu Lima de Souza Cascardo <cascardo@canonical.com>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Borislav Petkov <bpetkov@suse.de>
References: <20220722090650.665513668@linuxfoundation.org>
 <20220722090651.464856922@linuxfoundation.org>
From:   Jiri Slaby <jirislaby@kernel.org>
In-Reply-To: <20220722090651.464856922@linuxfoundation.org>
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Hi,

I wonder, why this is needed in stable and not mainline?

Isn't this a different (non-upstream) dup of
951ddecf4356 objtool: Treat .text.__x86.* as noinstr
? (That is included in this release too.)

On 22. 07. 22, 11:07, Greg Kroah-Hartman wrote:
> From: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
> 
> The .discard.text section is added in order to reserve BRK, with a
> temporary function just so it can give it a size. This adds a relocation to
> the return thunk, which objtool will add to the .return_sites section.
> Linking will then fail as there are references to the .discard.text
> section.
> 
> Do not add instructions from non-text sections to the list of return thunk
> calls, avoiding the reference to .discard.text.
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>   tools/objtool/check.c |    4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -1308,7 +1308,9 @@ static void add_return_call(struct objto
>   	insn->type = INSN_RETURN;
>   	insn->retpoline_safe = true;
>   
> -	list_add_tail(&insn->call_node, &file->return_thunk_list);
> +	/* Skip the non-text sections, specially .discard ones */
> +	if (insn->sec->text)
> +		list_add_tail(&insn->call_node, &file->return_thunk_list);
>   }
>   
>   static bool same_function(struct instruction *insn1, struct instruction *insn2)
> 
> 

thanks,
-- 
js
suse labs