Re: [PATCH 5.18 13/70] objtool: skip non-text sections when adding return-thunk sites

Jiri Slaby
2022-07-25T05:44:15Z

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