Commit 54a012b6 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'objtool-urgent-2025-04-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull misc objtool fixes from Ingo Molnar:

 - Remove the recently introduced ANNOTATE_IGNORE_ALTERNATIVE noise from
   clac()/stac() code to make .s files more readable

 - Fix INSN_SYSCALL / INSN_SYSRET semantics

 - Fix various false-positive warnings

* tag 'objtool-urgent-2025-04-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Fix false-positive "ignoring unreachables" warning
  objtool: Remove ANNOTATE_IGNORE_ALTERNATIVE from CLAC/STAC
  objtool, xen: Fix INSN_SYSCALL / INSN_SYSRET semantics
  objtool: Stop UNRET validation on UD2
  objtool: Split INSN_CONTEXT_SWITCH into INSN_SYSCALL and INSN_SYSRET
  objtool: Fix INSN_CONTEXT_SWITCH handling in validate_unret()
parents ab59a860 87cb582d

arch/x86/include/asm/smap.h

+6 −6
Original line number Diff line number Diff line
@@ -16,23 +16,23 @@ 
#ifdef __ASSEMBLER__



#define ASM_CLAC \

	ALTERNATIVE __stringify(ANNOTATE_IGNORE_ALTERNATIVE), "clac", X86_FEATURE_SMAP

	ALTERNATIVE "", "clac", X86_FEATURE_SMAP



#define ASM_STAC \

	ALTERNATIVE __stringify(ANNOTATE_IGNORE_ALTERNATIVE), "stac", X86_FEATURE_SMAP

	ALTERNATIVE "", "stac", X86_FEATURE_SMAP



#else /* __ASSEMBLER__ */



static __always_inline void clac(void)

{

	/* Note: a barrier is implicit in alternative() */

	alternative(ANNOTATE_IGNORE_ALTERNATIVE "", "clac", X86_FEATURE_SMAP);

	alternative("", "clac", X86_FEATURE_SMAP);

}



static __always_inline void stac(void)

{

	/* Note: a barrier is implicit in alternative() */

	alternative(ANNOTATE_IGNORE_ALTERNATIVE "", "stac", X86_FEATURE_SMAP);

	alternative("", "stac", X86_FEATURE_SMAP);

}



static __always_inline unsigned long smap_save(void)
@@ -59,9 +59,9 @@ static __always_inline void smap_restore(unsigned long flags) 


/* These macros can be used in asm() statements */

#define ASM_CLAC \

	ALTERNATIVE(ANNOTATE_IGNORE_ALTERNATIVE "", "clac", X86_FEATURE_SMAP)

	ALTERNATIVE("", "clac", X86_FEATURE_SMAP)

#define ASM_STAC \

	ALTERNATIVE(ANNOTATE_IGNORE_ALTERNATIVE "", "stac", X86_FEATURE_SMAP)

	ALTERNATIVE("", "stac", X86_FEATURE_SMAP)



#define ASM_CLAC_UNSAFE \

	ALTERNATIVE("", ANNOTATE_IGNORE_ALTERNATIVE "clac", X86_FEATURE_SMAP)

arch/x86/xen/xen-asm.S

+1 −3
Original line number Diff line number Diff line
@@ -226,9 +226,7 @@ SYM_CODE_END(xen_early_idt_handler_array) 
	push %rax

	mov  $__HYPERVISOR_iret, %eax

	syscall		/* Do the IRET. */

#ifdef CONFIG_MITIGATION_SLS

	int3

#endif

	ud2		/* The SYSCALL should never return. */

.endm



SYM_CODE_START(xen_iret)

tools/objtool/arch/x86/decode.c

+11 −7
Original line number Diff line number Diff line
@@ -522,7 +522,7 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec 
			case INAT_PFX_REPNE:

				if (modrm == 0xca)

					/* eretu/erets */

					insn->type = INSN_CONTEXT_SWITCH;

					insn->type = INSN_SYSRET;

				break;

			default:

				if (modrm == 0xca)
@@ -535,11 +535,15 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec 


			insn->type = INSN_JUMP_CONDITIONAL;



		} else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||

			   op2 == 0x35) {

		} else if (op2 == 0x05 || op2 == 0x34) {



			/* sysenter, sysret */

			insn->type = INSN_CONTEXT_SWITCH;

			/* syscall, sysenter */

			insn->type = INSN_SYSCALL;



		} else if (op2 == 0x07 || op2 == 0x35) {



			/* sysret, sysexit */

			insn->type = INSN_SYSRET;



		} else if (op2 == 0x0b || op2 == 0xb9) {
@@ -676,7 +680,7 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec 


	case 0xca: /* retf */

	case 0xcb: /* retf */

		insn->type = INSN_CONTEXT_SWITCH;

		insn->type = INSN_SYSRET;

		break;



	case 0xe0: /* loopne */
@@ -721,7 +725,7 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec 
		} else if (modrm_reg == 5) {



			/* jmpf */

			insn->type = INSN_CONTEXT_SWITCH;

			insn->type = INSN_SYSRET;



		} else if (modrm_reg == 6) {

tools/objtool/arch/x86/special.c

+1 −1
Original line number Diff line number Diff line
@@ -126,7 +126,7 @@ struct reloc *arch_find_switch_table(struct objtool_file *file, 
	 * indicates a rare GCC quirk/bug which can leave dead

	 * code behind.

	 */

	if (reloc_type(text_reloc) == R_X86_64_PC32) {

	if (!file->ignore_unreachables && reloc_type(text_reloc) == R_X86_64_PC32) {

		WARN_INSN(insn, "ignoring unreachables due to jump table quirk");

		file->ignore_unreachables = true;

	}

tools/objtool/check.c

+51 −8
Original line number Diff line number Diff line
@@ -3505,6 +3505,34 @@ static struct instruction *next_insn_to_validate(struct objtool_file *file, 
	return next_insn_same_sec(file, alt_group->orig_group->last_insn);

}



static bool skip_alt_group(struct instruction *insn)

{

	struct instruction *alt_insn = insn->alts ? insn->alts->insn : NULL;



	/* ANNOTATE_IGNORE_ALTERNATIVE */

	if (insn->alt_group && insn->alt_group->ignore)

		return true;



	/*

	 * For NOP patched with CLAC/STAC, only follow the latter to avoid

	 * impossible code paths combining patched CLAC with unpatched STAC

	 * or vice versa.

	 *

	 * ANNOTATE_IGNORE_ALTERNATIVE could have been used here, but Linus

	 * requested not to do that to avoid hurting .s file readability

	 * around CLAC/STAC alternative sites.

	 */



	if (!alt_insn)

		return false;



	/* Don't override ASM_{CLAC,STAC}_UNSAFE */

	if (alt_insn->alt_group && alt_insn->alt_group->ignore)

		return false;



	return alt_insn->type == INSN_CLAC || alt_insn->type == INSN_STAC;

}



/*

 * Follow the branch starting at the given instruction, and recursively follow

 * any other branches (jumps).  Meanwhile, track the frame pointer state at
@@ -3625,7 +3653,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 
			}

		}



		if (insn->alt_group && insn->alt_group->ignore)

		if (skip_alt_group(insn))

			return 0;



		if (handle_insn_ops(insn, next_insn, &state))
@@ -3684,14 +3712,20 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 


			break;



		case INSN_CONTEXT_SWITCH:

			if (func) {

				if (!next_insn || !next_insn->hint) {

		case INSN_SYSCALL:

			if (func && (!next_insn || !next_insn->hint)) {

				WARN_INSN(insn, "unsupported instruction in callable function");

				return 1;

			}



			break;



		case INSN_SYSRET:

			if (func && (!next_insn || !next_insn->hint)) {

				WARN_INSN(insn, "unsupported instruction in callable function");

				return 1;

			}



			return 0;



		case INSN_STAC:
@@ -3886,6 +3920,12 @@ static int validate_unret(struct objtool_file *file, struct instruction *insn) 
			WARN_INSN(insn, "RET before UNTRAIN");

			return 1;



		case INSN_SYSCALL:

			break;



		case INSN_SYSRET:

			return 0;



		case INSN_NOP:

			if (insn->retpoline_safe)

				return 0;
@@ -3895,6 +3935,9 @@ static int validate_unret(struct objtool_file *file, struct instruction *insn) 
			break;

		}



		if (insn->dead_end)

			return 0;



		if (!next) {

			WARN_INSN(insn, "teh end!");

			return 1;