linux-kernel - Re: [PATCH v2 52/62] objtool/klp: Introduce klp diff subcommand for diffing object files

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Message-ID: <20250526185716.GU24938@noisy.programming.kicks-ass.net>
Date: Mon, 26 May 2025 20:57:16 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org, Song Liu <song@...nel.org>,
	laokz <laokz@...mail.com>, Jiri Kosina <jikos@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Weinan Liu <wnliu@...gle.com>,
	Fazla Mehrab <a.mehrab@...edance.com>,
	Chen Zhongjin <chenzhongjin@...wei.com>,
	Puranjay Mohan <puranjay@...nel.org>
Subject: Re: [PATCH v2 52/62] objtool/klp: Introduce klp diff subcommand for
 diffing object files

On Fri, May 09, 2025 at 01:17:16PM -0700, Josh Poimboeuf wrote:
> diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
> index 4cfd09e66cb5..f62ac8081f27 100644
> --- a/tools/objtool/include/objtool/elf.h
> +++ b/tools/objtool/include/objtool/elf.h
> @@ -17,6 +17,7 @@
>  #include <objtool/checksum_types.h>
>  #include <arch/elf.h>
>  
> +#define SEC_NAME_LEN		512
>  #define SYM_NAME_LEN		512
>  
>  #ifdef LIBELF_USE_DEPRECATED
> @@ -50,10 +51,12 @@ struct section {
>  	bool _changed, text, rodata, noinstr, init, truncate;
>  	struct reloc *relocs;
>  	unsigned long nr_alloc_relocs;
> +	struct section *twin;
>  };
>  
>  struct symbol {
>  	struct list_head list;
> +	struct list_head global_list;
>  	struct rb_node node;
>  	struct elf_hash_node hash;
>  	struct elf_hash_node name_hash;
> @@ -79,10 +82,13 @@ struct symbol {
>  	u8 cold		     : 1;
>  	u8 prefix	     : 1;
>  	u8 debug_checksum    : 1;
> +	u8 changed	     : 1;
> +	u8 included	     : 1;
>  	struct list_head pv_target;
>  	struct reloc *relocs;
>  	struct section *group_sec;
>  	struct checksum csum;
> +	struct symbol *twin, *clone;
>  };
>  
>  struct reloc {
> @@ -100,6 +106,7 @@ struct elf {
>  	const char *name, *tmp_name;
>  	unsigned int num_files;
>  	struct list_head sections;
> +	struct list_head symbols;
>  	unsigned long num_relocs;
>  
>  	int symbol_bits;

ISTR us spending significant effort shrinking all this stuff. How does
this affect vmlinux.o memory footprint etc?