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Commit b1e03249 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

objtool: Detect infinite recursion 



I don't _think_ dead_end_function() can get into a recursive loop, but
just in case, stop the loop and print a warning.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris J Arges <chris.j.arges@canonical.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Pedro Alves <palves@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: live-patching@vger.kernel.org
Link: http://lkml.kernel.org/r/ff489a63e6feb88abb192cfb361d81626dcf3e89.1457502970.git.jpoimboe@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 81bfafca

tools/objtool/builtin-check.c

+33 −12
Original line number Diff line number Diff line
@@ -121,8 +121,14 @@ static bool ignore_func(struct objtool_file *file, struct symbol *func) 
 *

 * For local functions, we have to detect them manually by simply looking for

 * the lack of a return instruction.

 *

 * Returns:

 *  -1: error

 *   0: no dead end

 *   1: dead end

 */

static bool dead_end_function(struct objtool_file *file, struct symbol *func)

static int __dead_end_function(struct objtool_file *file, struct symbol *func,

			       int recursion)

{

	int i;

	struct instruction *insn, *func_insn;
@@ -144,19 +150,19 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) 
	};



	if (func->bind == STB_WEAK)

		return false;

		return 0;



	if (func->bind == STB_GLOBAL)

		for (i = 0; i < ARRAY_SIZE(global_noreturns); i++)

			if (!strcmp(func->name, global_noreturns[i]))

				return true;

				return 1;



	if (!func->sec)

		return false;

		return 0;



	func_insn = find_instruction(file, func->sec, func->offset);

	if (!func_insn)

		return false;

		return 0;



	insn = func_insn;

	list_for_each_entry_from(insn, &file->insns, list) {
@@ -167,11 +173,11 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) 
		empty = false;



		if (insn->type == INSN_RETURN)

			return false;

			return 0;

	}



	if (empty)

		return false;

		return 0;



	/*

	 * A function can have a sibling call instead of a return.  In that
@@ -190,7 +196,7 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) 


			if (!dest)

				/* sibling call to another file */

				return false;

				return 0;



			if (dest->sec != func->sec ||

			    dest->offset < func->offset ||
@@ -201,16 +207,28 @@ static bool dead_end_function(struct objtool_file *file, struct symbol *func) 
				if (!dest_func)

					continue;



				return dead_end_function(file, dest_func);

				if (recursion == 5) {

					WARN_FUNC("infinite recursion (objtool bug!)",

						  dest->sec, dest->offset);

					return -1;

				}



				return __dead_end_function(file, dest_func,

							   recursion + 1);

			}

		}



		if (insn->type == INSN_JUMP_DYNAMIC)

			/* sibling call */

			return false;

			return 0;

	}



	return true;

	return 1;

}



static int dead_end_function(struct objtool_file *file, struct symbol *func)

{

	return __dead_end_function(file, func, 0);

}



/*
@@ -809,8 +827,11 @@ static int validate_branch(struct objtool_file *file, 
				break;

			}



			if (dead_end_function(file, insn->call_dest))

			ret = dead_end_function(file, insn->call_dest);

			if (ret == 1)

				return warnings;

			if (ret == -1)

				warnings++;



			/* fallthrough */

		case INSN_CALL_DYNAMIC: