Commit ecf11ba4 authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool: Assume only ELF functions do sibling calls 



There's an inconsistency in how sibling calls are detected in
non-function asm code, depending on the scope of the object.  If the
target code is external to the object, objtool considers it a sibling
call.  If the target code is internal but not a function, objtool
*doesn't* consider it a sibling call.

This can cause some inconsistencies between per-object and vmlinux.o
validation.

Instead, assume only ELF functions can do sibling calls.  This generally
matches existing reality, and makes sibling call validation consistent
between vmlinux.o and per-object.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/0e9ab6f3628cc7bf3bde7aa6762d54d7df19ad78.1611263461.git.jpoimboe@redhat.com
parent 18660698

tools/objtool/check.c

+22 −14
Original line number Diff line number Diff line
@@ -110,15 +110,20 @@ static struct instruction *prev_insn_same_sym(struct objtool_file *file, 


static bool is_sibling_call(struct instruction *insn)

{

	/*

	 * Assume only ELF functions can make sibling calls.  This ensures

	 * sibling call detection consistency between vmlinux.o and individual

	 * objects.

	 */

	if (!insn->func)

		return false;



	/* An indirect jump is either a sibling call or a jump to a table. */

	if (insn->type == INSN_JUMP_DYNAMIC)

		return list_empty(&insn->alts);



	if (!is_static_jump(insn))

		return false;



	/* add_jump_destinations() sets insn->call_dest for sibling calls. */

	return !!insn->call_dest;

	return (is_static_jump(insn) && insn->call_dest);

}



/*
@@ -794,18 +799,21 @@ static int add_jump_destinations(struct objtool_file *file) 


			insn->retpoline_safe = true;

			continue;

		} else if (reloc->sym->sec->idx) {

			dest_sec = reloc->sym->sec;

			dest_off = reloc->sym->sym.st_value +

				   arch_dest_reloc_offset(reloc->addend);

		} else {

			/* external sibling call */

		} else if (insn->func) {

			/* internal or external sibling call (with reloc) */

			insn->call_dest = reloc->sym;

			if (insn->call_dest->static_call_tramp) {

				list_add_tail(&insn->static_call_node,

					      &file->static_call_list);

			}

			continue;

		} else if (reloc->sym->sec->idx) {

			dest_sec = reloc->sym->sec;

			dest_off = reloc->sym->sym.st_value +

				   arch_dest_reloc_offset(reloc->addend);

		} else {

			/* non-func asm code jumping to another file */

			continue;

		}



		insn->jump_dest = find_insn(file, dest_sec, dest_off);
@@ -854,7 +862,7 @@ static int add_jump_destinations(struct objtool_file *file) 
			} else if (insn->jump_dest->func->pfunc != insn->func->pfunc &&

				   insn->jump_dest->offset == insn->jump_dest->func->offset) {



				/* internal sibling call */

				/* internal sibling call (without reloc) */

				insn->call_dest = insn->jump_dest->func;

				if (insn->call_dest->static_call_tramp) {

					list_add_tail(&insn->static_call_node,
@@ -2587,7 +2595,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 


		case INSN_JUMP_CONDITIONAL:

		case INSN_JUMP_UNCONDITIONAL:

			if (func && is_sibling_call(insn)) {

			if (is_sibling_call(insn)) {

				ret = validate_sibling_call(insn, &state);

				if (ret)

					return ret;
@@ -2609,7 +2617,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 


		case INSN_JUMP_DYNAMIC:

		case INSN_JUMP_DYNAMIC_CONDITIONAL:

			if (func && is_sibling_call(insn)) {

			if (is_sibling_call(insn)) {

				ret = validate_sibling_call(insn, &state);

				if (ret)

					return ret;