[PATCH v2 3/6] x86/cpu: Remove CONFIG_X86_SMAP and "nosmap"

[Borislav Petkov <bp@alien8.de>]

From: Borislav Petkov <bp@suse.de>

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.

If still needed - clearcpuid=smap.

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
---
 .../admin-guide/kernel-parameters.txt         |  2 +-
 Documentation/x86/cpuinfo.rst                 |  5 ++--
 arch/x86/Kconfig                              | 11 ---------
 arch/x86/include/asm/disabled-features.h      |  8 +------
 arch/x86/include/asm/smap.h                   | 24 -------------------
 arch/x86/kernel/cpu/common.c                  | 15 +-----------
 scripts/Makefile.build                        |  1 -
 scripts/link-vmlinux.sh                       |  3 ---
 .../arch/x86/include/asm/disabled-features.h  |  8 +------
 9 files changed, 6 insertions(+), 71 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2b35a45c2fd3..04b155a4298f 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3394,7 +3394,7 @@
 			noexec=on: enable non-executable mappings (default)
 			noexec=off: disable non-executable mappings
 
-	nosmap		[X86,PPC]
+	nosmap		[PPC]
 			Disable SMAP (Supervisor Mode Access Prevention)
 			even if it is supported by processor.
 
diff --git a/Documentation/x86/cpuinfo.rst b/Documentation/x86/cpuinfo.rst
index 5d54c39a063f..12fbe2b1e98a 100644
--- a/Documentation/x86/cpuinfo.rst
+++ b/Documentation/x86/cpuinfo.rst
@@ -140,9 +140,8 @@ from #define X86_FEATURE_UMIP (16*32 + 2).
 
 In addition, there exists a variety of custom command-line parameters that
 disable specific features. The list of parameters includes, but is not limited
-to, nofsgsbase, nosmap, and nosmep. 5-level paging can also be disabled using
-"no5lvl". SMAP and SMEP are disabled with the aforementioned parameters,
-respectively.
+to, nofsgsbase, and nosmep. 5-level paging can also be disabled using
+"no5lvl". SMEP is disabled with the aforementioned parameter.
 
 e: The feature was known to be non-functional.
 ----------------------------------------------
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ebe8fc76949a..836fa757dbce 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1834,17 +1834,6 @@ 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 8f28fafa98b3..c2808f4d61f0 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
@@ -77,7 +71,7 @@
 #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 f394851db082..7e5d695279bc 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -304,13 +304,6 @@ 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();
@@ -318,14 +311,8 @@ 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)
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index a4b89b757287..9b37902607ed 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -233,7 +233,6 @@ objtool_args =								\
 	$(if $(CONFIG_FRAME_POINTER),, --no-fp)				\
 	$(if $(CONFIG_GCOV_KERNEL)$(CONFIG_LTO_CLANG), --no-unreachable)\
 	$(if $(CONFIG_RETPOLINE), --retpoline)				\
-	$(if $(CONFIG_X86_SMAP), --uaccess)				\
 	$(if $(CONFIG_FTRACE_MCOUNT_USE_OBJTOOL), --mcount)		\
 	$(if $(CONFIG_SLS), --sls)
 
diff --git a/scripts/link-vmlinux.sh b/scripts/link-vmlinux.sh
index 666f7bbc13eb..8547aaa1a630 100755
--- a/scripts/link-vmlinux.sh
+++ b/scripts/link-vmlinux.sh
@@ -140,9 +140,6 @@ objtool_link()
 		if is_enabled CONFIG_RETPOLINE; then
 			objtoolopt="${objtoolopt} --retpoline"
 		fi
-		if is_enabled CONFIG_X86_SMAP; then
-			objtoolopt="${objtoolopt} --uaccess"
-		fi
 		if is_enabled CONFIG_SLS; then
 			objtoolopt="${objtoolopt} --sls"
 		fi
diff --git a/tools/arch/x86/include/asm/disabled-features.h b/tools/arch/x86/include/asm/disabled-features.h
index 8f28fafa98b3..c2808f4d61f0 100644
--- a/tools/arch/x86/include/asm/disabled-features.h
+++ b/tools/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
@@ -77,7 +71,7 @@
 #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
-- 
2.29.2