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

arch/x86/Kconfig

+18 −5

Original line number	Diff line number	Diff line
		@@ -909,14 +909,27 @@ config VM86
		default y
		depends on X86_32
		---help---
		This option is required by programs like DOSEMU to run 16-bit legacy
		code on X86 processors. It also may be needed by software like
		XFree86 to initialize some video cards via BIOS. Disabling this
		option saves about 6k.
		This option is required by programs like DOSEMU to run
		16-bit real mode legacy code on x86 processors. It also may
		be needed by software like XFree86 to initialize some video
		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
		def_bool y
		depends on X86_64
		depends on X86_16BIT && X86_64

		config TOSHIBA
		tristate "Toshiba Laptop support"

arch/x86/kernel/entry_32.S

+12 −0

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

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

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

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

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

arch/x86/kernel/entry_64.S

+8 −0

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

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

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

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

		/*
		* End of kprobes section

arch/x86/kernel/ldt.c

+5 −0

Original line number	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);
		if (oldmode)
		ldt.avl = 0;

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