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Commit f8f25fde authored by Alexandre Chartre's avatar Alexandre Chartre Committed by Greg Kroah-Hartman
Browse files

objtool: Add support for intra-function calls 



commit 8aa8eb2a8f5b3305a95f39957dd2b715fa668e21 upstream.

Change objtool to support intra-function calls. On x86, an intra-function
call is represented in objtool as a push onto the stack (of the return
address), and a jump to the destination address. That way the stack
information is correctly updated and the call flow is still accurate.

Signed-off-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMiroslav Benes <mbenes@suse.cz>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200414103618.12657-4-alexandre.chartre@oracle.com


Signed-off-by: default avatarRui Qi <qirui.001@bytedance.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent eafb2936

include/linux/frame.h

+11 −0
Original line number Diff line number Diff line
@@ -15,9 +15,20 @@ 
	static void __used __section(.discard.func_stack_frame_non_standard) \

		*__func_stack_frame_non_standard_##func = func



/*

 * This macro indicates that the following intra-function call is valid.

 * Any non-annotated intra-function call will cause objtool to issue a warning.

 */

#define ANNOTATE_INTRA_FUNCTION_CALL				\

	999:							\

	.pushsection .discard.intra_function_calls;		\

	.long 999b;						\

	.popsection;



#else /* !CONFIG_STACK_VALIDATION */



#define STACK_FRAME_NON_STANDARD(func)

#define ANNOTATE_INTRA_FUNCTION_CALL



#endif /* CONFIG_STACK_VALIDATION */

tools/objtool/Documentation/stack-validation.txt

+8 −0
Original line number Diff line number Diff line
@@ -290,6 +290,14 @@ they mean, and suggestions for how to fix them. 
      https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70646





11. file.o: warning: unannotated intra-function call



   This warning means that a direct call is done to a destination which

   is not at the beginning of a function. If this is a legit call, you

   can remove this warning by putting the ANNOTATE_INTRA_FUNCTION_CALL

   directive right before the call.





If the error doesn't seem to make sense, it could be a bug in objtool.

Feel free to ask the objtool maintainer for help.

tools/objtool/arch/x86/decode.c

+6 −0
Original line number Diff line number Diff line
@@ -437,6 +437,12 @@ int arch_decode_instruction(struct elf *elf, struct section *sec, 


	case 0xe8:

		*type = INSN_CALL;

		/*

		 * For the impact on the stack, a CALL behaves like

		 * a PUSH of an immediate value (the return address).

		 */

			op->src.type = OP_SRC_CONST;

			op->dest.type = OP_DEST_PUSH;

		break;



	case 0xfc:

tools/objtool/check.c

+58 −4
Original line number Diff line number Diff line
@@ -645,6 +645,7 @@ static int add_jump_destinations(struct objtool_file *file) 
	return 0;

}





/*

 * Find the destination instructions for all calls.

 */
@@ -666,10 +667,7 @@ static int add_call_destinations(struct objtool_file *file) 
								dest_off);



			if (!insn->call_dest && !insn->ignore) {

				WARN_FUNC("unsupported intra-function call",

					  insn->sec, insn->offset);

				if (retpoline)

					WARN("If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.");

				WARN_FUNC("unannotated intra-function call", insn->sec, insn->offset);

				return -1;

			}
@@ -1291,6 +1289,58 @@ static int read_retpoline_hints(struct objtool_file *file) 
	return 0;

}





static int read_intra_function_calls(struct objtool_file *file)

{

	struct instruction *insn;

	struct section *sec;

	struct rela *rela;



	sec = find_section_by_name(file->elf, ".rela.discard.intra_function_calls");

	if (!sec)

		return 0;



	list_for_each_entry(rela, &sec->rela_list, list) {

		unsigned long dest_off;



		if (rela->sym->type != STT_SECTION) {

			WARN("unexpected relocation symbol type in %s",

			     sec->name);

			return -1;

		}



		insn = find_insn(file, rela->sym->sec, rela->addend);

		if (!insn) {

			WARN("bad .discard.intra_function_call entry");

			return -1;

		}



		if (insn->type != INSN_CALL) {

			WARN_FUNC("intra_function_call not a direct call",

				  insn->sec, insn->offset);

			return -1;

		}



		/*

		 * Treat intra-function CALLs as JMPs, but with a stack_op.

		 * See add_call_destinations(), which strips stack_ops from

		 * normal CALLs.

		 */

		insn->type = INSN_JUMP_UNCONDITIONAL;



		dest_off = insn->offset + insn->len + insn->immediate;

		insn->jump_dest = find_insn(file, insn->sec, dest_off);

		if (!insn->jump_dest) {

			WARN_FUNC("can't find call dest at %s+0x%lx",

				  insn->sec, insn->offset,

				  insn->sec->name, dest_off);

			return -1;

		}

	}



	return 0;

}



static void mark_rodata(struct objtool_file *file)

{

	struct section *sec;
@@ -1346,6 +1396,10 @@ static int decode_sections(struct objtool_file *file) 
	if (ret)

		return ret;



	ret = read_intra_function_calls(file);

	if (ret)

		return ret;



	ret = add_call_destinations(file);

	if (ret)

		return ret;