linux-kernel - Re: [PATCH v4 01/10] objtool: Handle various symbol types of rodata

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Message-ID: <20241126064458.7ugwqfx5vhnwzvbi@jpoimboe>
Date: Mon, 25 Nov 2024 22:44:58 -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 01/10] objtool: Handle various symbol types of rodata

On Fri, Nov 22, 2024 at 12:49:56PM +0800, Tiezhu Yang wrote:
> @@ -2094,12 +2095,19 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
>  		if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
>  			break;
>  
> +		if (reloc->sym->type == STT_SECTION) {
> +			/* Addend field in the relocation entry associated with the symbol */
> +			offset = reloc_addend(reloc);
> +		} else {
> +			/* The address of the symbol in the relocation entry */
> +			offset = reloc->sym->offset;

The comments don't seem helpful.

In the case of STT_SECTION, sym->offset is always zero.  Therefore the
if-else can be converted to a simple unconditional statement:

	offset = reloc->sym->offset + reloc_addend(reloc);

'prev_offset' needs to be updated as well.

> @@ -2137,6 +2145,7 @@ static struct reloc *find_jump_table(struct objtool_file *file,
>  {
>  	struct reloc *table_reloc;
>  	struct instruction *dest_insn, *orig_insn = insn;
> +	unsigned long offset;
>  
>  	/*
>  	 * Backward search using the @first_jump_src links, these help avoid
> @@ -2160,7 +2169,16 @@ static struct reloc *find_jump_table(struct objtool_file *file,
>  		table_reloc = arch_find_switch_table(file, insn);
>  		if (!table_reloc)
>  			continue;
> -		dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
> +
> +		if (table_reloc->sym->type == STT_SECTION) {
> +			/* Addend field in the relocation entry associated with the symbol */
> +			offset = reloc_addend(table_reloc);
> +		} else {
> +			/* The address of the symbol in the relocation entry */
> +			offset = table_reloc->sym->offset;
> +		}

Same comment here.

-- 
Josh