Commit fdabdd0b authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Provide elf_write_{insn,reloc}() 



This provides infrastructure to rewrite instructions; this is
immediately useful for helping out with KCOV-vs-noinstr, but will
also come in handy for a bunch of variable sized jump-label patches
that are still on ice.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent 2b10be23

tools/objtool/elf.c

+39 −1
Original line number Diff line number Diff line
@@ -529,8 +529,9 @@ static int read_relas(struct elf *elf) 
			rela->addend = rela->rela.r_addend;

			rela->offset = rela->rela.r_offset;

			symndx = GELF_R_SYM(rela->rela.r_info);

			rela->sym = find_symbol_by_index(elf, symndx);

			rela->sec = sec;

			rela->idx = i;

			rela->sym = find_symbol_by_index(elf, symndx);

			if (!rela->sym) {

				WARN("can't find rela entry symbol %d for %s",

				     symndx, sec->name);
@@ -784,6 +785,43 @@ int elf_rebuild_rela_section(struct elf *elf, struct section *sec) 
	return 0;

}



int elf_write_insn(struct elf *elf, struct section *sec,

		   unsigned long offset, unsigned int len,

		   const char *insn)

{

	Elf_Data *data = sec->data;



	if (data->d_type != ELF_T_BYTE || data->d_off) {

		WARN("write to unexpected data for section: %s", sec->name);

		return -1;

	}



	memcpy(data->d_buf + offset, insn, len);

	elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY);



	elf->changed = true;



	return 0;

}



int elf_write_rela(struct elf *elf, struct rela *rela)

{

	struct section *sec = rela->sec;



	rela->rela.r_info = GELF_R_INFO(rela->sym->idx, rela->type);

	rela->rela.r_addend = rela->addend;

	rela->rela.r_offset = rela->offset;



	if (!gelf_update_rela(sec->data, rela->idx, &rela->rela)) {

		WARN_ELF("gelf_update_rela");

		return -1;

	}



	elf->changed = true;



	return 0;

}



int elf_write(struct elf *elf)

{

	struct section *sec;

tools/objtool/elf.h

+6 −1
Original line number Diff line number Diff line
@@ -64,9 +64,10 @@ struct rela { 
	GElf_Rela rela;

	struct section *sec;

	struct symbol *sym;

	unsigned int type;

	unsigned long offset;

	unsigned int type;

	int addend;

	int idx;

	bool jump_table_start;

};
@@ -119,6 +120,10 @@ struct elf *elf_open_read(const char *name, int flags); 
struct section *elf_create_section(struct elf *elf, const char *name, size_t entsize, int nr);

struct section *elf_create_rela_section(struct elf *elf, struct section *base);

void elf_add_rela(struct elf *elf, struct rela *rela);

int elf_write_insn(struct elf *elf, struct section *sec,

		   unsigned long offset, unsigned int len,

		   const char *insn);

int elf_write_rela(struct elf *elf, struct rela *rela);

int elf_write(struct elf *elf);

void elf_close(struct elf *elf);