Commit 87d6021b authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Borislav Petkov
Browse files

x86/math-emu: Limit MATH_EMULATION to 486SX compatibles 



The FPU emulation code is old and fragile in places, try to limit its
use to builds for CPUs that actually use it. As far as I can tell,
this is only true for i486sx compatibles, including the Cyrix 486SLC,
AMD Am486SX and ÉLAN SC410, UMC U5S amd DM&P VortexSX86, all of which
were relatively short-lived and got replaced with i486DX compatible
processors soon after introduction, though some of the embedded versions
remained available much longer.

Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Bill Metzenthen <billm@melbpc.org.au>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86-ml <x86@kernel.org>
Link: https://lkml.kernel.org/r/20191001142344.1274185-2-arnd@arndb.de
parent e6b44ce1

arch/x86/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -1751,7 +1751,7 @@ config X86_RESERVE_LOW 
config MATH_EMULATION

	bool

	depends on MODIFY_LDT_SYSCALL

	prompt "Math emulation" if X86_32

	prompt "Math emulation" if X86_32 && (M486SX || MELAN)

	---help---

	  Linux can emulate a math coprocessor (used for floating point

	  operations) if you don't have one. 486DX and Pentium processors have

arch/x86/Kconfig.cpu

+16 −9
Original line number Diff line number Diff line
@@ -50,12 +50,19 @@ choice 
	  See each option's help text for additional details. If you don't know

	  what to do, choose "486".



config M486SX

	bool "486SX"

	depends on X86_32

	---help---

	  Select this for an 486-class CPU without an FPU such as

	  AMD/Cyrix/IBM/Intel SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5S.



config M486

	bool "486"

	bool "486DX"

	depends on X86_32

	---help---

	  Select this for an 486-class CPU such as AMD/Cyrix/IBM/Intel

	  486DX/DX2/DX4 or SL/SLC/SLC2/SLC3/SX/SX2 and UMC U5D or U5S.

	  486DX/DX2/DX4 and UMC U5D.



config M586

	bool "586/K5/5x86/6x86/6x86MX"
@@ -312,20 +319,20 @@ config X86_L1_CACHE_SHIFT 
	int

	default "7" if MPENTIUM4 || MPSC

	default "6" if MK7 || MK8 || MPENTIUMM || MCORE2 || MATOM || MVIAC7 || X86_GENERIC || GENERIC_CPU

	default "4" if MELAN || M486 || MGEODEGX1

	default "4" if MELAN || M486SX || M486 || MGEODEGX1

	default "5" if MWINCHIP3D || MWINCHIPC6 || MCRUSOE || MEFFICEON || MCYRIXIII || MK6 || MPENTIUMIII || MPENTIUMII || M686 || M586MMX || M586TSC || M586 || MVIAC3_2 || MGEODE_LX



config X86_F00F_BUG

	def_bool y

	depends on M586MMX || M586TSC || M586 || M486

	depends on M586MMX || M586TSC || M586 || M486SX || M486



config X86_INVD_BUG

	def_bool y

	depends on M486

	depends on M486SX || M486



config X86_ALIGNMENT_16

	def_bool y

	depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MELAN || MK6 || M586MMX || M586TSC || M586 || M486 || MVIAC3_2 || MGEODEGX1

	depends on MWINCHIP3D || MWINCHIPC6 || MCYRIXIII || MELAN || MK6 || M586MMX || M586TSC || M586 || M486SX || M486 || MVIAC3_2 || MGEODEGX1



config X86_INTEL_USERCOPY

	def_bool y
@@ -378,7 +385,7 @@ config X86_MINIMUM_CPU_FAMILY 


config X86_DEBUGCTLMSR

	def_bool y

	depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586 || M486) && !UML

	depends on !(MK6 || MWINCHIPC6 || MWINCHIP3D || MCYRIXIII || M586MMX || M586TSC || M586 || M486SX || M486) && !UML



menuconfig PROCESSOR_SELECT

	bool "Supported processor vendors" if EXPERT
@@ -402,7 +409,7 @@ config CPU_SUP_INTEL 
config CPU_SUP_CYRIX_32

	default y

	bool "Support Cyrix processors" if PROCESSOR_SELECT

	depends on M486 || M586 || M586TSC || M586MMX || (EXPERT && !64BIT)

	depends on M486SX || M486 || M586 || M586TSC || M586MMX || (EXPERT && !64BIT)

	---help---

	  This enables detection, tunings and quirks for Cyrix processors
@@ -470,7 +477,7 @@ config CPU_SUP_TRANSMETA_32 
config CPU_SUP_UMC_32

	default y

	bool "Support UMC processors" if PROCESSOR_SELECT

	depends on M486 || (EXPERT && !64BIT)

	depends on M486SX || M486 || (EXPERT && !64BIT)

	---help---

	  This enables detection, tunings and quirks for UMC processors

arch/x86/Makefile_32.cpu

+1 −0
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ else 
tune		= $(call cc-option,-mcpu=$(1),$(2))

endif



cflags-$(CONFIG_M486SX)		+= -march=i486

cflags-$(CONFIG_M486)		+= -march=i486

cflags-$(CONFIG_M586)		+= -march=i586

cflags-$(CONFIG_M586TSC)	+= -march=i586

arch/x86/include/asm/module.h

+2 −0
Original line number Diff line number Diff line
@@ -15,6 +15,8 @@ struct mod_arch_specific { 


#ifdef CONFIG_X86_64

/* X86_64 does not define MODULE_PROC_FAMILY */

#elif defined CONFIG_M486SX

#define MODULE_PROC_FAMILY "486SX "

#elif defined CONFIG_M486

#define MODULE_PROC_FAMILY "486 "

#elif defined CONFIG_M586

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