linux-kernel - [PATCH] x86: Kill some chicken bits

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Date:	Tue, 20 Oct 2015 18:33:30 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: Kill some chicken bits

From: Borislav Petkov <bp@...e.de>

Those were added as, well, chicken bits in case some of those features
are b0rked and as a way for us to "chicken" out and disable them. Remove
those chicken bits now, as they're not needed anymore.

Requested-by: "H. Peter Anvin" <hpa@...or.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
---
 Documentation/kernel-parameters.txt | 10 ----------
 arch/x86/kernel/cpu/common.c        | 22 ----------------------
 2 files changed, 32 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 22a4b687ea5b..0448d63e3269 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2362,8 +2362,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	nocache		[ARM]
 
-	noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
-
 	nodelayacct	[KNL] Disable per-task delay accounting
 
 	nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
@@ -2379,14 +2377,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			noexec=on: enable non-executable mappings (default)
 			noexec=off: disable non-executable mappings
 
-	nosmap		[X86]
-			Disable SMAP (Supervisor Mode Access Prevention)
-			even if it is supported by processor.
-
-	nosmep		[X86]
-			Disable SMEP (Supervisor Mode Execution Prevention)
-			even if it is supported by processor.
-
 	noexec32	[X86-64]
 			This affects only 32-bit executables.
 			noexec32=on: enable non-executable mappings (default)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index de22ea7ff82f..610c84379d87 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -251,26 +251,12 @@ static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
 }
 #endif
 
-static __init int setup_disable_smep(char *arg)
-{
-	setup_clear_cpu_cap(X86_FEATURE_SMEP);
-	return 1;
-}
-__setup("nosmep", setup_disable_smep);
-
 static __always_inline void setup_smep(struct cpuinfo_x86 *c)
 {
 	if (cpu_has(c, X86_FEATURE_SMEP))
 		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;
@@ -1083,14 +1069,6 @@ static __init int setup_show_msr(char *arg)
 }
 __setup("show_msr=", setup_show_msr);
 
-static __init int setup_noclflush(char *arg)
-{
-	setup_clear_cpu_cap(X86_FEATURE_CLFLUSH);
-	setup_clear_cpu_cap(X86_FEATURE_CLFLUSHOPT);
-	return 1;
-}
-__setup("noclflush", setup_noclflush);
-
 void print_cpu_info(struct cpuinfo_x86 *c)
 {
 	const char *vendor = NULL;
-- 
2.3.5

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