x86, espfix: Make it possible to disable 16-bit support (34273f41) · Commits · e / devices / android_kernel_fairphone_FP3

arch/x86/Kconfig

+18 −5

Original line number	Original line	Diff line number	Diff line
	@@ -909,14 +909,27 @@ config VM86
	default y		default y
	depends on X86_32		depends on X86_32
	---help---		---help---
	This option is required by programs like DOSEMU to run 16-bit legacy		This option is required by programs like DOSEMU to run
	code on X86 processors. It also may be needed by software like		16-bit real mode legacy code on x86 processors. It also may
	XFree86 to initialize some video cards via BIOS. Disabling this		be needed by software like XFree86 to initialize some video
	option saves about 6k.		cards via BIOS. Disabling this option saves about 6K.

			config X86_16BIT
			bool "Enable support for 16-bit segments" if EXPERT
			default y
			---help---
			This option is required by programs like Wine to run 16-bit
			protected mode legacy code on x86 processors. Disabling
			this option saves about 300 bytes on i386, or around 6K text
			plus 16K runtime memory on x86-64,

			config X86_ESPFIX32
			def_bool y
			depends on X86_16BIT && X86_32

	config X86_ESPFIX64		config X86_ESPFIX64
	def_bool y		def_bool y
	depends on X86_64		depends on X86_16BIT && X86_64

	config TOSHIBA		config TOSHIBA
	tristate "Toshiba Laptop support"		tristate "Toshiba Laptop support"

arch/x86/kernel/entry_32.S

+12 −0

Original line number	Original line	Diff line number	Diff line
	@@ -527,6 +527,7 @@ syscall_exit:
	restore_all:		restore_all:
	TRACE_IRQS_IRET		TRACE_IRQS_IRET
	restore_all_notrace:		restore_all_notrace:
			#ifdef CONFIG_X86_ESPFIX32
	movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS		movl PT_EFLAGS(%esp), %eax # mix EFLAGS, SS and CS
	# Warning: PT_OLDSS(%esp) contains the wrong/random values if we		# Warning: PT_OLDSS(%esp) contains the wrong/random values if we
	# are returning to the kernel.		# are returning to the kernel.
	@@ -537,6 +538,7 @@ restore_all_notrace:
	cmpl $((SEGMENT_LDT << 8) \| USER_RPL), %eax		cmpl $((SEGMENT_LDT << 8) \| USER_RPL), %eax
	CFI_REMEMBER_STATE		CFI_REMEMBER_STATE
	je ldt_ss # returning to user-space with LDT SS		je ldt_ss # returning to user-space with LDT SS
			#endif
	restore_nocheck:		restore_nocheck:
	RESTORE_REGS 4 # skip orig_eax/error_code		RESTORE_REGS 4 # skip orig_eax/error_code
	irq_return:		irq_return:
	@@ -549,6 +551,7 @@ ENTRY(iret_exc)
	.previous		.previous
	_ASM_EXTABLE(irq_return,iret_exc)		_ASM_EXTABLE(irq_return,iret_exc)

			#ifdef CONFIG_X86_ESPFIX32
	CFI_RESTORE_STATE		CFI_RESTORE_STATE
	ldt_ss:		ldt_ss:
	#ifdef CONFIG_PARAVIRT		#ifdef CONFIG_PARAVIRT
	@@ -592,6 +595,7 @@ ldt_ss:
	lss (%esp), %esp /* switch to espfix segment */		lss (%esp), %esp /* switch to espfix segment */
	CFI_ADJUST_CFA_OFFSET -8		CFI_ADJUST_CFA_OFFSET -8
	jmp restore_nocheck		jmp restore_nocheck
			#endif
	CFI_ENDPROC		CFI_ENDPROC
	ENDPROC(system_call)		ENDPROC(system_call)

	@@ -699,6 +703,7 @@ END(syscall_badsys)
	* the high word of the segment base from the GDT and swiches to the		* the high word of the segment base from the GDT and swiches to the
	* normal stack and adjusts ESP with the matching offset.		* normal stack and adjusts ESP with the matching offset.
	*/		*/
			#ifdef CONFIG_X86_ESPFIX32
	/* fixup the stack */		/* fixup the stack */
	mov GDT_ESPFIX_SS + 4, %al /* bits 16..23 */		mov GDT_ESPFIX_SS + 4, %al /* bits 16..23 */
	mov GDT_ESPFIX_SS + 7, %ah /* bits 24..31 */		mov GDT_ESPFIX_SS + 7, %ah /* bits 24..31 */
	@@ -708,8 +713,10 @@ END(syscall_badsys)
	pushl_cfi %eax		pushl_cfi %eax
	lss (%esp), %esp /* switch to the normal stack segment */		lss (%esp), %esp /* switch to the normal stack segment */
	CFI_ADJUST_CFA_OFFSET -8		CFI_ADJUST_CFA_OFFSET -8
			#endif
	.endm		.endm
	.macro UNWIND_ESPFIX_STACK		.macro UNWIND_ESPFIX_STACK
			#ifdef CONFIG_X86_ESPFIX32
	movl %ss, %eax		movl %ss, %eax
	/* see if on espfix stack */		/* see if on espfix stack */
	cmpw $__ESPFIX_SS, %ax		cmpw $__ESPFIX_SS, %ax
	@@ -720,6 +727,7 @@ END(syscall_badsys)
	/* switch to normal stack */		/* switch to normal stack */
	FIXUP_ESPFIX_STACK		FIXUP_ESPFIX_STACK
	27:		27:
			#endif
	.endm		.endm

	/*		/*
	@@ -1350,11 +1358,13 @@ END(debug)
	ENTRY(nmi)		ENTRY(nmi)
	RING0_INT_FRAME		RING0_INT_FRAME
	ASM_CLAC		ASM_CLAC
			#ifdef CONFIG_X86_ESPFIX32
	pushl_cfi %eax		pushl_cfi %eax
	movl %ss, %eax		movl %ss, %eax
	cmpw $__ESPFIX_SS, %ax		cmpw $__ESPFIX_SS, %ax
	popl_cfi %eax		popl_cfi %eax
	je nmi_espfix_stack		je nmi_espfix_stack
			#endif
	cmpl $ia32_sysenter_target,(%esp)		cmpl $ia32_sysenter_target,(%esp)
	je nmi_stack_fixup		je nmi_stack_fixup
	pushl_cfi %eax		pushl_cfi %eax
	@@ -1394,6 +1404,7 @@ nmi_debug_stack_check:
	FIX_STACK 24, nmi_stack_correct, 1		FIX_STACK 24, nmi_stack_correct, 1
	jmp nmi_stack_correct		jmp nmi_stack_correct

			#ifdef CONFIG_X86_ESPFIX32
	nmi_espfix_stack:		nmi_espfix_stack:
	/* We have a RING0_INT_FRAME here.		/* We have a RING0_INT_FRAME here.
	*		*
	@@ -1415,6 +1426,7 @@ nmi_espfix_stack:
	lss 12+4(%esp), %esp # back to espfix stack		lss 12+4(%esp), %esp # back to espfix stack
	CFI_ADJUST_CFA_OFFSET -24		CFI_ADJUST_CFA_OFFSET -24
	jmp irq_return		jmp irq_return
			#endif
	CFI_ENDPROC		CFI_ENDPROC
	END(nmi)		END(nmi)

arch/x86/kernel/entry_64.S

+8 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1045,8 +1045,10 @@ irq_return:
	* Are we returning to a stack segment from the LDT? Note: in		* Are we returning to a stack segment from the LDT? Note: in
	* 64-bit mode SS:RSP on the exception stack is always valid.		* 64-bit mode SS:RSP on the exception stack is always valid.
	*/		*/
			#ifdef CONFIG_X86_ESPFIX64
	testb $4,(SS-RIP)(%rsp)		testb $4,(SS-RIP)(%rsp)
	jnz irq_return_ldt		jnz irq_return_ldt
			#endif

	irq_return_iret:		irq_return_iret:
	INTERRUPT_RETURN		INTERRUPT_RETURN
	@@ -1058,6 +1060,7 @@ ENTRY(native_iret)
	_ASM_EXTABLE(native_iret, bad_iret)		_ASM_EXTABLE(native_iret, bad_iret)
	#endif		#endif

			#ifdef CONFIG_X86_ESPFIX64
	irq_return_ldt:		irq_return_ldt:
	pushq_cfi %rax		pushq_cfi %rax
	pushq_cfi %rdi		pushq_cfi %rdi
	@@ -1081,6 +1084,7 @@ irq_return_ldt:
	movq %rax,%rsp		movq %rax,%rsp
	popq_cfi %rax		popq_cfi %rax
	jmp irq_return_iret		jmp irq_return_iret
			#endif

	.section .fixup,"ax"		.section .fixup,"ax"
	bad_iret:		bad_iret:
	@@ -1152,6 +1156,7 @@ END(common_interrupt)
	* modify the stack to make it look like we just entered		* modify the stack to make it look like we just entered
	* the #GP handler from user space, similar to bad_iret.		* the #GP handler from user space, similar to bad_iret.
	*/		*/
			#ifdef CONFIG_X86_ESPFIX64
	ALIGN		ALIGN
	__do_double_fault:		__do_double_fault:
	XCPT_FRAME 1 RDI+8		XCPT_FRAME 1 RDI+8
	@@ -1177,6 +1182,9 @@ __do_double_fault:
	retq		retq
	CFI_ENDPROC		CFI_ENDPROC
	END(__do_double_fault)		END(__do_double_fault)
			#else
			# define __do_double_fault do_double_fault
			#endif

	/*		/*
	* End of kprobes section		* End of kprobes section

arch/x86/kernel/ldt.c

+5 −0

Original line number	Original line	Diff line number	Diff line
	@@ -229,6 +229,11 @@ static int write_ldt(void __user *ptr, unsigned long bytecount, int oldmode)
	}		}
	}		}

			if (!IS_ENABLED(CONFIG_X86_16BIT) && !ldt_info.seg_32bit) {
			error = -EINVAL;
			goto out_unlock;
			}

	fill_ldt(&ldt, &ldt_info);		fill_ldt(&ldt, &ldt_info);
	if (oldmode)		if (oldmode)
	ldt.avl = 0;		ldt.avl = 0;