diff mbox series

[2/2] x86: math-emu: limit MATH_EMULATION to 486SX compatibles

Message ID 20191001142344.1274185-2-arnd@arndb.de
State New
Headers show
Series [1/2] x86: math-emu: check __copy_from_user result | expand

Commit Message

Arnd Bergmann Oct. 1, 2019, 2:23 p.m. UTC 
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 the some of the embedded
versions remained available much longer.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
 arch/x86/Kconfig              |  2 +-
 arch/x86/Kconfig.cpu          | 25 ++++++++++++++++---------
 arch/x86/Makefile_32.cpu      |  1 +
 arch/x86/include/asm/module.h |  2 ++
 4 files changed, 20 insertions(+), 10 deletions(-)

-- 
2.20.0

Comments

Kees Cook Oct. 1, 2019, 9:54 p.m. UTC | #1 
On Tue, Oct 01, 2019 at 04:23:35PM +0200, Arnd Bergmann wrote:
> 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 the some of the embedded

> versions remained available much longer.

> 

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>


Nice, I like carving out CONFIG space for 486SX; this makes sense to me.

Reviewed-by: Kees Cook <keescook@chromium.org>


-Kees

> ---

>  arch/x86/Kconfig              |  2 +-

>  arch/x86/Kconfig.cpu          | 25 ++++++++++++++++---------

>  arch/x86/Makefile_32.cpu      |  1 +

>  arch/x86/include/asm/module.h |  2 ++

>  4 files changed, 20 insertions(+), 10 deletions(-)

> 

> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig

> index f4d9d1e55e5c..77b02387bd0c 100644

> --- a/arch/x86/Kconfig

> +++ b/arch/x86/Kconfig

> @@ -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

> diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu

> index 228705a1232a..5f7bff9885a1 100644

> --- a/arch/x86/Kconfig.cpu

> +++ b/arch/x86/Kconfig.cpu

> @@ -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"

> @@ -313,20 +320,20 @@ 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

> @@ -379,7 +386,7 @@ 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

> @@ -403,7 +410,7 @@ 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

>  

> @@ -471,7 +478,7 @@ 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

>  

> diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu

> index 1f5faf8606b4..cd3056759880 100644

> --- a/arch/x86/Makefile_32.cpu

> +++ b/arch/x86/Makefile_32.cpu

> @@ -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

> diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h

> index 7948a17febb4..c215d2762488 100644

> --- a/arch/x86/include/asm/module.h

> +++ b/arch/x86/include/asm/module.h

> @@ -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

> -- 

> 2.20.0

> 


-- 
Kees Cook
diff mbox series

Patch

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f4d9d1e55e5c..77b02387bd0c 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -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
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu
index 228705a1232a..5f7bff9885a1 100644
--- a/arch/x86/Kconfig.cpu
+++ b/arch/x86/Kconfig.cpu
@@ -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"
@@ -313,20 +320,20 @@  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
@@ -379,7 +386,7 @@  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
@@ -403,7 +410,7 @@  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
 
@@ -471,7 +478,7 @@  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
 
diff --git a/arch/x86/Makefile_32.cpu b/arch/x86/Makefile_32.cpu
index 1f5faf8606b4..cd3056759880 100644
--- a/arch/x86/Makefile_32.cpu
+++ b/arch/x86/Makefile_32.cpu
@@ -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
diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h
index 7948a17febb4..c215d2762488 100644
--- a/arch/x86/include/asm/module.h
+++ b/arch/x86/include/asm/module.h
@@ -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