Commit 8045b8f0 authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Josh Poimboeuf
Browse files

objtool: Allocate multiple structures with calloc() 



By using calloc() instead of malloc() in a loop, libc does not have to
keep around bookkeeping information for each single structure.

This reduces maximum memory usage while processing vmlinux.o from
3153325 KB to 3035668 KB (-3.7%) on my notebooks "localmodconfig".

Note this introduces memory leaks, because some additional structs get
added to the lists later after reading the symbols and sections from the
original object.  Luckily we don't really care about memory leaks in
objtool.

Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20221216-objtool-memory-v2-3-17968f85a464@weissschuh.net


Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent cfd66e81

tools/objtool/elf.c

+21 −21
Original line number Diff line number Diff line
@@ -284,13 +284,13 @@ static int read_sections(struct elf *elf) 
	    !elf_alloc_hash(section_name, sections_nr))

		return -1;



	for (i = 0; i < sections_nr; i++) {

		sec = malloc(sizeof(*sec));

		if (!sec) {

			perror("malloc");

	elf->section_data = calloc(sections_nr, sizeof(*sec));

	if (!elf->section_data) {

		perror("calloc");

		return -1;

	}

		memset(sec, 0, sizeof(*sec));

	for (i = 0; i < sections_nr; i++) {

		sec = &elf->section_data[i];



		INIT_LIST_HEAD(&sec->symbol_list);

		INIT_LIST_HEAD(&sec->reloc_list);
@@ -422,13 +422,13 @@ static int read_symbols(struct elf *elf) 
	    !elf_alloc_hash(symbol_name, symbols_nr))

		return -1;



	for (i = 0; i < symbols_nr; i++) {

		sym = malloc(sizeof(*sym));

		if (!sym) {

			perror("malloc");

	elf->symbol_data = calloc(symbols_nr, sizeof(*sym));

	if (!elf->symbol_data) {

		perror("calloc");

		return -1;

	}

		memset(sym, 0, sizeof(*sym));

	for (i = 0; i < symbols_nr; i++) {

		sym = &elf->symbol_data[i];



		sym->idx = i;
@@ -918,13 +918,13 @@ static int read_relocs(struct elf *elf) 
		sec->base->reloc = sec;



		nr_reloc = 0;

		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {

			reloc = malloc(sizeof(*reloc));

			if (!reloc) {

				perror("malloc");

		sec->reloc_data = calloc(sec->sh.sh_size / sec->sh.sh_entsize, sizeof(*reloc));

		if (!sec->reloc_data) {

			perror("calloc");

			return -1;

		}

			memset(reloc, 0, sizeof(*reloc));

		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {

			reloc = &sec->reloc_data[i];

			switch (sec->sh.sh_type) {

			case SHT_REL:

				if (read_rel_reloc(sec, i, reloc, &symndx))
@@ -1453,16 +1453,16 @@ void elf_close(struct elf *elf) 
		list_for_each_entry_safe(sym, tmpsym, &sec->symbol_list, list) {

			list_del(&sym->list);

			hash_del(&sym->hash);

			free(sym);

		}

		list_for_each_entry_safe(reloc, tmpreloc, &sec->reloc_list, list) {

			list_del(&reloc->list);

			hash_del(&reloc->hash);

			free(reloc);

		}

		list_del(&sec->list);

		free(sec);

		free(sec->reloc_data);

	}



	free(elf->symbol_data);

	free(elf->section_data);

	free(elf);

}

tools/objtool/include/objtool/elf.h

+4 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ struct section { 
	char *name;

	int idx;

	bool changed, text, rodata, noinstr, init, truncate;

	struct reloc *reloc_data;

};



struct symbol {
@@ -104,6 +105,9 @@ struct elf { 
	struct hlist_head *section_hash;

	struct hlist_head *section_name_hash;

	struct hlist_head *reloc_hash;



	struct section *section_data;

	struct symbol *symbol_data;

};



#define OFFSET_STRIDE_BITS	4