Commit 08ef8c40 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Allow symbol range comparisons for IBT/ENDBR 



A semi common pattern is where code checks if a code address is
within a specific range. All text addresses require either ENDBR or
ANNOTATE_ENDBR, however the ANNOTATE_NOENDBR past the range is
unnatural.

Instead, suppress this warning when this is exactly at the end of a
symbol that itself starts with either ENDBR/ANNOTATE_ENDBR.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111146.434642471@infradead.org
parent 5da6aea3

arch/x86/entry/entry_64_compat.S

+0 −1
Original line number Diff line number Diff line
@@ -128,7 +128,6 @@ SYM_INNER_LABEL(entry_SYSENTER_compat_after_hwframe, SYM_L_GLOBAL) 
	popfq

	jmp	.Lsysenter_flags_fixed

SYM_INNER_LABEL(__end_entry_SYSENTER_compat, SYM_L_GLOBAL)

	ANNOTATE_NOENDBR // is_sysenter_singlestep

SYM_CODE_END(entry_SYSENTER_compat)



/*

tools/objtool/check.c

+28 −0
Original line number Diff line number Diff line
@@ -4033,6 +4033,24 @@ static void mark_endbr_used(struct instruction *insn) 
		list_del_init(&insn->call_node);

}



static bool noendbr_range(struct objtool_file *file, struct instruction *insn)

{

	struct symbol *sym = find_symbol_containing(insn->sec, insn->offset-1);

	struct instruction *first;



	if (!sym)

		return false;



	first = find_insn(file, sym->sec, sym->offset);

	if (!first)

		return false;



	if (first->type != INSN_ENDBR && !first->noendbr)

		return false;



	return insn->offset == sym->offset + sym->len;

}



static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn)

{

	struct instruction *dest;
@@ -4105,9 +4123,19 @@ static int validate_ibt_insn(struct objtool_file *file, struct instruction *insn 
			continue;

		}



		/*

		 * Accept anything ANNOTATE_NOENDBR.

		 */

		if (dest->noendbr)

			continue;



		/*

		 * Accept if this is the instruction after a symbol

		 * that is (no)endbr -- typical code-range usage.

		 */

		if (noendbr_range(file, dest))

			continue;



		WARN_FUNC("relocation to !ENDBR: %s",

			  insn->sec, insn->offset,

			  offstr(dest->sec, dest->offset));