x86/cpu: Remove CONFIG_X86_SMAP and "nosmap"

Those were added as part of the SMAP enablement but SMAP is currently
an integral part of kernel proper and there's no need to disable it
anymore.

Rip out that functionality. Leave --uaccess default on for objtool as
this is what objtool should do by default anyway.

If still needed - clearcpuid=smap.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220127115626.14179-4-bp@alien8.de

4 files changed, 2 insertions, 56 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b0142e01002e..5bc8bee64bb0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1816,17 +1816,6 @@ config ARCH_RANDOM
 	  If supported, this is a high bandwidth, cryptographically
 	  secure hardware random number generator.
 
-config X86_SMAP
-	def_bool y
-	prompt "Supervisor Mode Access Prevention" if EXPERT
-	help
-	  Supervisor Mode Access Prevention (SMAP) is a security
-	  feature in newer Intel processors.  There is a small
-	  performance cost if this enabled and turned on; there is
-	  also a small increase in the kernel size if this is enabled.
-
-	  If unsure, say Y.
-
 config X86_UMIP
 	def_bool y
 	prompt "User Mode Instruction Prevention" if EXPERT
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 1231d63f836d..1ae0fab7d902 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -10,12 +10,6 @@
  * cpu_feature_enabled().
  */
 
-#ifdef CONFIG_X86_SMAP
-# define DISABLE_SMAP	0
-#else
-# define DISABLE_SMAP	(1<<(X86_FEATURE_SMAP & 31))
-#endif
-
 #ifdef CONFIG_X86_UMIP
 # define DISABLE_UMIP	0
 #else
@@ -80,7 +74,7 @@
 #define DISABLED_MASK6	0
 #define DISABLED_MASK7	(DISABLE_PTI)
 #define DISABLED_MASK8	0
-#define DISABLED_MASK9	(DISABLE_SMAP|DISABLE_SGX)
+#define DISABLED_MASK9	(DISABLE_SGX)
 #define DISABLED_MASK10	0
 #define DISABLED_MASK11	0
 #define DISABLED_MASK12	0
diff --git a/arch/x86/include/asm/smap.h b/arch/x86/include/asm/smap.h
index d17b39893b79..bab490379c65 100644
--- a/arch/x86/include/asm/smap.h
+++ b/arch/x86/include/asm/smap.h
@@ -19,25 +19,14 @@
 
 #ifdef __ASSEMBLY__
 
-#ifdef CONFIG_X86_SMAP
-
 #define ASM_CLAC \
 	ALTERNATIVE "", __ASM_CLAC, X86_FEATURE_SMAP
 
 #define ASM_STAC \
 	ALTERNATIVE "", __ASM_STAC, X86_FEATURE_SMAP
 
-#else /* CONFIG_X86_SMAP */
-
-#define ASM_CLAC
-#define ASM_STAC
-
-#endif /* CONFIG_X86_SMAP */
-
 #else /* __ASSEMBLY__ */
 
-#ifdef CONFIG_X86_SMAP
-
 static __always_inline void clac(void)
 {
 	/* Note: a barrier is implicit in alternative() */
@@ -76,19 +65,6 @@ static __always_inline void smap_restore(unsigned long flags)
 #define ASM_STAC \
 	ALTERNATIVE("", __ASM_STAC, X86_FEATURE_SMAP)
 
-#else /* CONFIG_X86_SMAP */
-
-static inline void clac(void) { }
-static inline void stac(void) { }
-
-static inline unsigned long smap_save(void) { return 0; }
-static inline void smap_restore(unsigned long flags) { }
-
-#define ASM_CLAC
-#define ASM_STAC
-
-#endif /* CONFIG_X86_SMAP */
-
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_X86_SMAP_H */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c71d1075db93..747df070fb5e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -382,13 +382,6 @@ static __always_inline void setup_smep(struct cpuinfo_x86 *c)
 		cr4_set_bits(X86_CR4_SMEP);
 }
 
-static __init int setup_disable_smap(char *arg)
-{
-	setup_clear_cpu_cap(X86_FEATURE_SMAP);
-	return 1;
-}
-__setup("nosmap", setup_disable_smap);
-
 static __always_inline void setup_smap(struct cpuinfo_x86 *c)
 {
 	unsigned long eflags = native_save_fl();
@@ -396,14 +389,8 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c)
 	/* This should have been cleared long ago */
 	BUG_ON(eflags & X86_EFLAGS_AC);
 
-	if (cpu_has(c, X86_FEATURE_SMAP)) {
-#ifdef CONFIG_X86_SMAP
+	if (cpu_has(c, X86_FEATURE_SMAP))
 		cr4_set_bits(X86_CR4_SMAP);
-#else
-		clear_cpu_cap(c, X86_FEATURE_SMAP);
-		cr4_clear_bits(X86_CR4_SMAP);
-#endif
-	}
 }
 
 static __always_inline void setup_umip(struct cpuinfo_x86 *c)