Commit a706bb08 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

objtool: Fix overlapping alternatives 



Things like ALTERNATIVE_{2,3}() generate multiple alternatives on the
same place, objtool would override the first orig_alt_group with the
second (or third), failing to check the CFI among all the different
variants.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build only
Tested-by: Thomas Weißschuh <linux@weissschuh.net> # compile and run
Link: https://lore.kernel.org/r/20230208172245.711471461@infradead.org
parent c6f5dc28

tools/objtool/check.c

+43 −26
Original line number Diff line number Diff line
@@ -1744,10 +1744,13 @@ static int handle_group_alt(struct objtool_file *file, 
			    struct instruction *orig_insn,

			    struct instruction **new_insn)

{

	struct instruction *last_orig_insn, *last_new_insn = NULL, *insn, *nop = NULL;

	struct instruction *last_new_insn = NULL, *insn, *nop = NULL;

	struct alt_group *orig_alt_group, *new_alt_group;

	unsigned long dest_off;



	orig_alt_group = orig_insn->alt_group;

	if (!orig_alt_group) {

		struct instruction *last_orig_insn = NULL;



		orig_alt_group = malloc(sizeof(*orig_alt_group));

		if (!orig_alt_group) {
@@ -1761,7 +1764,6 @@ static int handle_group_alt(struct objtool_file *file, 
			return -1;

		}



	last_orig_insn = NULL;

		insn = orig_insn;

		sec_for_each_insn_from(file, insn) {

			if (insn->offset >= special_alt->orig_off + special_alt->orig_len)
@@ -1773,7 +1775,18 @@ static int handle_group_alt(struct objtool_file *file, 
		orig_alt_group->orig_group = NULL;

		orig_alt_group->first_insn = orig_insn;

		orig_alt_group->last_insn = last_orig_insn;



	} else {

		if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -

		    orig_alt_group->first_insn->offset != special_alt->orig_len) {

			WARN_FUNC("weirdly overlapping alternative! %ld != %d",

				  orig_insn->sec, orig_insn->offset,

				  orig_alt_group->last_insn->offset +

				  orig_alt_group->last_insn->len -

				  orig_alt_group->first_insn->offset,

				  special_alt->orig_len);

			return -1;

		}

	}



	new_alt_group = malloc(sizeof(*new_alt_group));

	if (!new_alt_group) {
@@ -1848,7 +1861,7 @@ static int handle_group_alt(struct objtool_file *file, 


		dest_off = arch_jump_destination(insn);

		if (dest_off == special_alt->new_off + special_alt->new_len) {

			insn->jump_dest = next_insn_same_sec(file, last_orig_insn);

			insn->jump_dest = next_insn_same_sec(file, orig_alt_group->last_insn);

			if (!insn->jump_dest) {

				WARN_FUNC("can't find alternative jump destination",

					  insn->sec, insn->offset);
@@ -3226,8 +3239,12 @@ static int propagate_alt_cfi(struct objtool_file *file, struct instruction *insn 
		alt_cfi[group_off] = insn->cfi;

	} else {

		if (cficmp(alt_cfi[group_off], insn->cfi)) {

			WARN_FUNC("stack layout conflict in alternatives",

				  insn->sec, insn->offset);

			struct alt_group *orig_group = insn->alt_group->orig_group ?: insn->alt_group;

			struct instruction *orig = orig_group->first_insn;

			char *where = offstr(insn->sec, insn->offset);

			WARN_FUNC("stack layout conflict in alternatives: %s",

				  orig->sec, orig->offset, where);

			free(where);

			return -1;

		}

	}