Commit dd2c29aa authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool: Generalize elf_create_symbol() 



In preparation for the objtool klp diff subcommand, broaden the
elf_create_symbol() interface to give callers more control and reduce
duplication of some subtle setup logic.

While at it, make elf_create_symbol() and elf_create_section_symbol()
global so sections can be created by the upcoming klp diff code.

Acked-by: default avatarPetr Mladek <pmladek@suse.com>
Tested-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent 02cf323a

tools/objtool/elf.c

+59 −52
Original line number Diff line number Diff line
@@ -763,24 +763,60 @@ static int elf_update_symbol(struct elf *elf, struct section *symtab, 
	return 0;

}



static struct symbol *

__elf_create_symbol(struct elf *elf, struct symbol *sym)

static int elf_add_string(struct elf *elf, struct section *strtab, const char *str);



struct symbol *elf_create_symbol(struct elf *elf, const char *name,

				 struct section *sec, unsigned int bind,

				 unsigned int type, unsigned long offset,

				 size_t size)

{

	struct section *symtab, *symtab_shndx;

	Elf32_Word first_non_local, new_idx;

	struct symbol *old;

	struct symbol *old, *sym;



	symtab = find_section_by_name(elf, ".symtab");

	if (symtab) {

		symtab_shndx = find_section_by_name(elf, ".symtab_shndx");

	sym = calloc(1, sizeof(*sym));

	if (!sym) {

		ERROR_GLIBC("calloc");

		return NULL;

	}



	sym->name = strdup(name);

	if (!sym->name) {

		ERROR_GLIBC("strdup");

		return NULL;

	}



	if (type != STT_SECTION) {

		sym->sym.st_name = elf_add_string(elf, NULL, sym->name);

		if (sym->sym.st_name == -1)

			return NULL;

	}



	if (sec) {

		sym->sec = sec;

	} else {

		sym->sec = find_section_by_index(elf, 0);

		if (!sym->sec) {

			ERROR("no NULL section");

			return NULL;

		}

	}



	sym->sym.st_info  = GELF_ST_INFO(bind, type);

	sym->sym.st_value = offset;

	sym->sym.st_size  = size;



	symtab = find_section_by_name(elf, ".symtab");

	if (!symtab) {

		ERROR("no .symtab");

		return NULL;

	}



	symtab_shndx = find_section_by_name(elf, ".symtab_shndx");



	new_idx = sec_num_entries(symtab);



	if (GELF_ST_BIND(sym->sym.st_info) != STB_LOCAL)

	if (bind != STB_LOCAL)

		goto non_local;



	/*
@@ -818,10 +854,8 @@ __elf_create_symbol(struct elf *elf, struct symbol *sym) 


non_local:

	sym->idx = new_idx;

	if (elf_update_symbol(elf, symtab, symtab_shndx, sym)) {

		ERROR("elf_update_symbol");

	if (sym->idx && elf_update_symbol(elf, symtab, symtab_shndx, sym))

		return NULL;

	}



	symtab->sh.sh_size += symtab->sh.sh_entsize;

	mark_sec_changed(elf, symtab, true);
@@ -831,64 +865,39 @@ __elf_create_symbol(struct elf *elf, struct symbol *sym) 
		mark_sec_changed(elf, symtab_shndx, true);

	}



	elf_add_symbol(elf, sym);



	return sym;

}



static struct symbol *

elf_create_section_symbol(struct elf *elf, struct section *sec)

struct symbol *elf_create_section_symbol(struct elf *elf, struct section *sec)

{

	struct symbol *sym = calloc(1, sizeof(*sym));



	if (!sym) {

		ERROR_GLIBC("malloc");

	sym = elf_create_symbol(elf, sec->name, sec, STB_LOCAL, STT_SECTION, 0, 0);

	if (!sym)

		return NULL;

	}



	sym->name = sec->name;

	sym->sec = sec;



	// st_name 0

	sym->sym.st_info = GELF_ST_INFO(STB_LOCAL, STT_SECTION);

	// st_other 0

	// st_value 0

	// st_size 0



	sym = __elf_create_symbol(elf, sym);

	if (sym)

		elf_add_symbol(elf, sym);

	sec->sym = sym;



	return sym;

}



static int elf_add_string(struct elf *elf, struct section *strtab, const char *str);



struct symbol *

elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size)

elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, size_t size)

{

	struct symbol *sym = calloc(1, sizeof(*sym));

	size_t namelen = strlen(orig->name) + sizeof("__pfx_");

	char *name = malloc(namelen);



	if (!sym || !name) {

		ERROR_GLIBC("malloc");

		return NULL;

	}

	char name[SYM_NAME_LEN];

	unsigned long offset;



	snprintf(name, namelen, "__pfx_%s", orig->name);



	sym->name = name;

	sym->sec = orig->sec;

	offset = orig->sym.st_value - size;



	sym->sym.st_name = elf_add_string(elf, NULL, name);

	sym->sym.st_info = orig->sym.st_info;

	sym->sym.st_value = orig->sym.st_value - size;

	sym->sym.st_size = size;



	sym = __elf_create_symbol(elf, sym);

	if (sym)

		elf_add_symbol(elf, sym);



	return sym;

	return elf_create_symbol(elf, name, orig->sec,

				 GELF_ST_BIND(orig->sym.st_info),

				 GELF_ST_TYPE(orig->sym.st_info),

				 offset, size);

}



static struct reloc *elf_init_reloc(struct elf *elf, struct section *rsec,
@@ -934,7 +943,7 @@ struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec, 
				      unsigned long insn_off)

{

	struct symbol *sym = insn_sec->sym;

	int addend = insn_off;

	s64 addend = insn_off;



	if (!is_text_sec(insn_sec)) {

		ERROR("bad call to %s() for data symbol %s", __func__, sym->name);
@@ -951,8 +960,6 @@ struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec, 
		sym = elf_create_section_symbol(elf, insn_sec);

		if (!sym)

			return NULL;



		insn_sec->sym = sym;

	}



	return elf_init_reloc(elf, sec->rsec, reloc_idx, offset, sym, addend,

tools/objtool/include/objtool/elf.h

+10 −1
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ 
#include <linux/jhash.h>

#include <arch/elf.h>



#define SYM_NAME_LEN		512



#ifdef LIBELF_USE_DEPRECATED

# define elf_getshdrnum    elf_getshnum

# define elf_getshdrstrndx elf_getshstrndx
@@ -120,7 +122,14 @@ struct section *elf_create_section_pair(struct elf *elf, const char *name, 
					size_t entsize, unsigned int nr,

					unsigned int reloc_nr);



struct symbol *elf_create_prefix_symbol(struct elf *elf, struct symbol *orig, long size);

struct symbol *elf_create_symbol(struct elf *elf, const char *name,

				 struct section *sec, unsigned int bind,

				 unsigned int type, unsigned long offset,

				 size_t size);

struct symbol *elf_create_section_symbol(struct elf *elf, struct section *sec);

struct symbol *elf_create_prefix_symbol(struct elf *elf, struct symbol *orig,

					size_t size);





struct reloc *elf_init_reloc_text_sym(struct elf *elf, struct section *sec,

				      unsigned long offset,