Commit 86ea7f36 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

objtool: Use target file class size instead of a compiled constant 



In order to allow using objtool on cross-built kernels,
determine size of long from elf data instead of using
sizeof(long) at build time.

For the time being this covers only mcount.

[Sathvika Vasireddy: Rename variable "size" to "addrsize" and function
"elf_class_size()" to "elf_class_addrsize()", and modify
create_mcount_loc_sections() function to follow reverse christmas tree
format to order local variable declarations.]

Tested-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarSathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221114175754.1131267-11-sv@linux.ibm.com
parent 0646c28b

tools/objtool/check.c

+10 −8
Original line number Diff line number Diff line
@@ -852,9 +852,9 @@ static int create_ibt_endbr_seal_sections(struct objtool_file *file) 


static int create_mcount_loc_sections(struct objtool_file *file)

{

	struct section *sec;

	unsigned long *loc;

	int addrsize = elf_class_addrsize(file->elf);

	struct instruction *insn;

	struct section *sec;

	int idx;



	sec = find_section_by_name(file->elf, "__mcount_loc");
@@ -871,23 +871,25 @@ static int create_mcount_loc_sections(struct objtool_file *file) 
	list_for_each_entry(insn, &file->mcount_loc_list, call_node)

		idx++;



	sec = elf_create_section(file->elf, "__mcount_loc", 0, sizeof(unsigned long), idx);

	sec = elf_create_section(file->elf, "__mcount_loc", 0, addrsize, idx);

	if (!sec)

		return -1;



	sec->sh.sh_addralign = addrsize;



	idx = 0;

	list_for_each_entry(insn, &file->mcount_loc_list, call_node) {

		void *loc;



		loc = (unsigned long *)sec->data->d_buf + idx;

		memset(loc, 0, sizeof(unsigned long));

		loc = sec->data->d_buf + idx;

		memset(loc, 0, addrsize);



		if (elf_add_reloc_to_insn(file->elf, sec,

					  idx * sizeof(unsigned long),

		if (elf_add_reloc_to_insn(file->elf, sec, idx,

					  R_X86_64_64,

					  insn->sec, insn->offset))

			return -1;



		idx++;

		idx += addrsize;

	}



	return 0;

tools/objtool/elf.c

+6 −2
Original line number Diff line number Diff line
@@ -1129,6 +1129,7 @@ static struct section *elf_create_rela_reloc_section(struct elf *elf, struct sec 
{

	char *relocname;

	struct section *sec;

	int addrsize = elf_class_addrsize(elf);



	relocname = malloc(strlen(base->name) + strlen(".rela") + 1);

	if (!relocname) {
@@ -1138,6 +1139,9 @@ static struct section *elf_create_rela_reloc_section(struct elf *elf, struct sec 
	strcpy(relocname, ".rela");

	strcat(relocname, base->name);



	if (addrsize == sizeof(u32))

		sec = elf_create_section(elf, relocname, 0, sizeof(Elf32_Rela), 0);

	else

		sec = elf_create_section(elf, relocname, 0, sizeof(GElf_Rela), 0);

	free(relocname);

	if (!sec)
@@ -1147,7 +1151,7 @@ static struct section *elf_create_rela_reloc_section(struct elf *elf, struct sec 
	sec->base = base;



	sec->sh.sh_type = SHT_RELA;

	sec->sh.sh_addralign = 8;

	sec->sh.sh_addralign = addrsize;

	sec->sh.sh_link = find_section_by_name(elf, ".symtab")->idx;

	sec->sh.sh_info = base->idx;

	sec->sh.sh_flags = SHF_INFO_LINK;

tools/objtool/include/objtool/elf.h

+8 −0
Original line number Diff line number Diff line
@@ -142,6 +142,14 @@ static inline bool has_multiple_files(struct elf *elf) 
	return elf->num_files > 1;

}



static inline int elf_class_addrsize(struct elf *elf)

{

	if (elf->ehdr.e_ident[EI_CLASS] == ELFCLASS32)

		return sizeof(u32);

	else

		return sizeof(u64);

}



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

struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr);