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

[Peter Zijlstra <peterz@infradead.org>]

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?