linux-kernel - Re: [PATCH v4 05/10] objtool: Handle unreachable entry of rodata

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Message-ID: <20241126072557.b6qt7jaiikvkcswn@jpoimboe>
Date: Mon, 25 Nov 2024 23:25:57 -0800
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Huacai Chen <chenhuacai@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 05/10] objtool: Handle unreachable entry of rodata

On Fri, Nov 22, 2024 at 12:50:00PM +0800, Tiezhu Yang wrote:
> When compling with Clang on LoongArch, there exists unreachable entry of
> rodata which points to a position after the function return instruction,
> this is generated by compiler to fill the non-existent switch case, just
> skip the entry when parsing the relocation section of rodata.
> 
> This is preparation for later patch on LoongArch, there is no effect for
> the other archs with this patch.
> 
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
>  tools/objtool/check.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 8733ca620cca..b21e47d8d3d1 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -2144,6 +2144,13 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
>  		if (!dest_insn)
>  			break;
>  
> +		/* Handle the special cases compiled with Clang on LoongArch */
> +		if (file->elf->ehdr.e_machine == EM_LOONGARCH && reloc->sym->type == STT_SECTION &&
> +		    (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)) {
> +			prev_offset = reloc_offset(reloc);
> +			continue;

Are you sure this is specific to loongarch?

-- 
Josh