Commit 03c19a99 authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool: Add elf_create_file() 



Add interface to enable the creation of a new ELF file.

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 2c05ca02

tools/objtool/builtin-check.c

+1 −1
Original line number Diff line number Diff line
@@ -329,5 +329,5 @@ int objtool_run(int argc, const char **argv) 
	if (!opts.dryrun && file->elf->changed && elf_write(file->elf))

		return 1;



	return 0;

	return elf_close(file->elf);

}

tools/objtool/elf.c

+143 −1
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <string.h>

#include <unistd.h>

#include <errno.h>

#include <libgen.h>

#include <linux/interval_tree_generic.h>

#include <objtool/builtin.h>

#include <objtool/elf.h>
@@ -1067,6 +1068,12 @@ struct elf *elf_open_read(const char *name, int flags) 
		goto err;

	}



	elf->name = strdup(name);

	if (!elf->name) {

		ERROR_GLIBC("strdup");

		return NULL;

	}



	if ((flags & O_ACCMODE) == O_RDONLY)

		cmd = ELF_C_READ_MMAP;

	else if ((flags & O_ACCMODE) == O_RDWR)
@@ -1104,6 +1111,137 @@ struct elf *elf_open_read(const char *name, int flags) 
	return NULL;

}



struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name)

{

	struct section *null, *symtab, *strtab, *shstrtab;

	char *dir, *base, *tmp_name;

	struct symbol *sym;

	struct elf *elf;



	elf_version(EV_CURRENT);



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

	if (!elf) {

		ERROR_GLIBC("calloc");

		return NULL;

	}



	INIT_LIST_HEAD(&elf->sections);



	dir = strdup(name);

	if (!dir) {

		ERROR_GLIBC("strdup");

		return NULL;

	}



	dir = dirname(dir);



	base = strdup(name);

	if (!base) {

		ERROR_GLIBC("strdup");

		return NULL;

	}



	base = basename(base);



	tmp_name = malloc(256);

	if (!tmp_name) {

		ERROR_GLIBC("malloc");

		return NULL;

	}



	snprintf(tmp_name, 256, "%s/%s.XXXXXX", dir, base);



	elf->fd = mkstemp(tmp_name);

	if (elf->fd == -1) {

		ERROR_GLIBC("can't create tmp file");

		exit(1);

	}



	elf->tmp_name = tmp_name;



	elf->name = strdup(name);

	if (!elf->name) {

		ERROR_GLIBC("strdup");

		return NULL;

	}



	elf->elf = elf_begin(elf->fd, ELF_C_WRITE, NULL);

	if (!elf->elf) {

		ERROR_ELF("elf_begin");

		return NULL;

	}



	if (!gelf_newehdr(elf->elf, ELFCLASS64)) {

		ERROR_ELF("gelf_newehdr");

		return NULL;

	}



	memcpy(&elf->ehdr, ehdr, sizeof(elf->ehdr));



	if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) {

		ERROR_ELF("gelf_update_ehdr");

		return NULL;

	}



	if (!elf_alloc_hash(section,		1000) ||

	    !elf_alloc_hash(section_name,	1000) ||

	    !elf_alloc_hash(symbol,		10000) ||

	    !elf_alloc_hash(symbol_name,	10000) ||

	    !elf_alloc_hash(reloc,		100000))

		return NULL;



	null		= elf_create_section(elf, NULL, 0, 0, SHT_NULL, 0, 0);

	shstrtab	= elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0);

	strtab		= elf_create_section(elf, NULL, 0, 0, SHT_STRTAB, 1, 0);



	if (!null || !shstrtab || !strtab)

		return NULL;



	null->name	= "";

	shstrtab->name	= ".shstrtab";

	strtab->name	= ".strtab";



	null->sh.sh_name	= elf_add_string(elf, shstrtab, null->name);

	shstrtab->sh.sh_name	= elf_add_string(elf, shstrtab, shstrtab->name);

	strtab->sh.sh_name	= elf_add_string(elf, shstrtab, strtab->name);



	if (null->sh.sh_name == -1 || shstrtab->sh.sh_name == -1 || strtab->sh.sh_name == -1)

		return NULL;



	elf_hash_add(section_name, &null->name_hash,		str_hash(null->name));

	elf_hash_add(section_name, &strtab->name_hash,		str_hash(strtab->name));

	elf_hash_add(section_name, &shstrtab->name_hash,	str_hash(shstrtab->name));



	if (elf_add_string(elf, strtab, "") == -1)

		return NULL;



	symtab = elf_create_section(elf, ".symtab", 0x18, 0x18, SHT_SYMTAB, 0x8, 0);

	if (!symtab)

		return NULL;



	symtab->sh.sh_link = strtab->idx;

	symtab->sh.sh_info = 1;



	elf->ehdr.e_shstrndx = shstrtab->idx;

	if (!gelf_update_ehdr(elf->elf, &elf->ehdr)) {

		ERROR_ELF("gelf_update_ehdr");

		return NULL;

	}



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

	if (!sym) {

		ERROR_GLIBC("calloc");

		return NULL;

	}



	sym->name = "";

	sym->sec = null;

	elf_add_symbol(elf, sym);



	return elf;

}



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

{

	unsigned int offset;
@@ -1568,7 +1706,7 @@ int elf_write(struct elf *elf) 
	return 0;

}



void elf_close(struct elf *elf)

int elf_close(struct elf *elf)

{

	if (elf->elf)

		elf_end(elf->elf);
@@ -1576,8 +1714,12 @@ void elf_close(struct elf *elf) 
	if (elf->fd > 0)

		close(elf->fd);



	if (elf->tmp_name && rename(elf->tmp_name, elf->name))

		return -1;



	/*

	 * NOTE: All remaining allocations are leaked on purpose.  Objtool is

	 * about to exit anyway.

	 */

	return 0;

}

tools/objtool/include/objtool/elf.h

+3 −2
Original line number Diff line number Diff line
@@ -94,7 +94,7 @@ struct elf { 
	GElf_Ehdr ehdr;

	int fd;

	bool changed;

	const char *name;

	const char *name, *tmp_name;

	unsigned int num_files;

	struct list_head sections;

	unsigned long num_relocs;
@@ -116,6 +116,7 @@ struct elf { 
};



struct elf *elf_open_read(const char *name, int flags);

struct elf *elf_create_file(GElf_Ehdr *ehdr, const char *name);



struct section *elf_create_section(struct elf *elf, const char *name,

				   size_t size, size_t entsize,
@@ -165,7 +166,7 @@ int elf_write_insn(struct elf *elf, struct section *sec, unsigned long offset, 
		   unsigned int len, const char *insn);



int elf_write(struct elf *elf);

void elf_close(struct elf *elf);

int elf_close(struct elf *elf);



struct section *find_section_by_name(const struct elf *elf, const char *name);

struct symbol *find_func_by_offset(struct section *sec, unsigned long offset);