Commit dd003ede authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Explicitly avoid self modifying code in .altinstr_replacement 



Assume ALTERNATIVE()s know what they're doing and do not change, or
cause to change, instructions in .altinstr_replacement sections.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Tested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120309.722511775@infradead.org
parent 1739c66e

tools/objtool/check.c

+31 −11
Original line number Diff line number Diff line
@@ -993,18 +993,27 @@ static void remove_insn_ops(struct instruction *insn) 
	}

}



static void add_call_dest(struct objtool_file *file, struct instruction *insn,

			  struct symbol *dest, bool sibling)

static void annotate_call_site(struct objtool_file *file,

			       struct instruction *insn, bool sibling)

{

	struct reloc *reloc = insn_reloc(file, insn);

	struct symbol *sym = insn->call_dest;



	insn->call_dest = dest;

	if (!dest)

	if (!sym)

		sym = reloc->sym;



	/*

	 * Alternative replacement code is just template code which is

	 * sometimes copied to the original instruction. For now, don't

	 * annotate it. (In the future we might consider annotating the

	 * original instruction if/when it ever makes sense to do so.)

	 */

	if (!strcmp(insn->sec->name, ".altinstr_replacement"))

		return;



	if (insn->call_dest->static_call_tramp) {

		list_add_tail(&insn->call_node,

			      &file->static_call_list);

	if (sym->static_call_tramp) {

		list_add_tail(&insn->call_node, &file->static_call_list);

		return;

	}



	/*
@@ -1012,7 +1021,7 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn, 
	 * so they need a little help, NOP out any KCOV calls from noinstr

	 * text.

	 */

	if (insn->sec->noinstr && insn->call_dest->kcov) {

	if (insn->sec->noinstr && sym->kcov) {

		if (reloc) {

			reloc->type = R_NONE;

			elf_write_reloc(file->elf, reloc);
@@ -1024,9 +1033,10 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn, 
			               : arch_nop_insn(insn->len));



		insn->type = sibling ? INSN_RETURN : INSN_NOP;

		return;

	}



	if (mcount && insn->call_dest->fentry) {

	if (mcount && sym->fentry) {

		if (sibling)

			WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset);
@@ -1041,10 +1051,18 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn, 


		insn->type = INSN_NOP;



		list_add_tail(&insn->mcount_loc_node,

			      &file->mcount_loc_list);

		list_add_tail(&insn->mcount_loc_node, &file->mcount_loc_list);

		return;

	}

}



static void add_call_dest(struct objtool_file *file, struct instruction *insn,

			  struct symbol *dest, bool sibling)

{

	insn->call_dest = dest;

	if (!dest)

		return;



	/*

	 * Whatever stack impact regular CALLs have, should be undone

	 * by the RETURN of the called function.
@@ -1053,6 +1071,8 @@ static void add_call_dest(struct objtool_file *file, struct instruction *insn, 
	 * are converted to JUMP, see read_intra_function_calls().

	 */

	remove_insn_ops(insn);



	annotate_call_site(file, insn, sibling);

}



/*