Commit e27e5bea authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Paolo Bonzini
Browse files

x86/ibt, objtool: Add IBT_NOSEAL() 



Add a macro which prevents a function from getting sealed if there are
no compile-time references to it.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Message-Id: <20220818213927.e44fmxkoq4yj6ybn@treble>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 20ec3ebd

arch/x86/include/asm/ibt.h

+11 −0
Original line number Diff line number Diff line
@@ -31,6 +31,16 @@ 


#define __noendbr	__attribute__((nocf_check))



/*

 * Create a dummy function pointer reference to prevent objtool from marking

 * the function as needing to be "sealed" (i.e. ENDBR converted to NOP by

 * apply_ibt_endbr()).

 */

#define IBT_NOSEAL(fname)				\

	".pushsection .discard.ibt_endbr_noseal\n\t"	\

	_ASM_PTR fname "\n\t"				\

	".popsection\n\t"



static inline __attribute_const__ u32 gen_endbr(void)

{

	u32 endbr;
@@ -84,6 +94,7 @@ extern __noendbr void ibt_restore(u64 save); 
#ifndef __ASSEMBLY__



#define ASM_ENDBR

#define IBT_NOSEAL(name)



#define __noendbr

tools/objtool/check.c

+2 −1
Original line number Diff line number Diff line
@@ -4096,7 +4096,8 @@ static int validate_ibt(struct objtool_file *file) 
		 * These sections can reference text addresses, but not with

		 * the intent to indirect branch to them.

		 */

		if (!strncmp(sec->name, ".discard", 8)			||

		if ((!strncmp(sec->name, ".discard", 8) &&

		     strcmp(sec->name, ".discard.ibt_endbr_noseal"))	||

		    !strncmp(sec->name, ".debug", 6)			||

		    !strcmp(sec->name, ".altinstructions")		||

		    !strcmp(sec->name, ".ibt_endbr_seal")		||