linux-kernel - [PATCH] x86/fsgsbase: Replace static_cpu_has() with boot_cpu

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Message-Id: <20200818103715.32736-1-bp@alien8.de>
Date:   Tue, 18 Aug 2020 12:37:15 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/fsgsbase: Replace static_cpu_has() with boot_cpu_has()

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

ptrace and prctl() are not really fast paths to warrant the use of
static_cpu_has() and cause alternatives patching for no good reason.
Replace with boot_cpu_has() which is simple and fast enough.

No functional changes.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/include/asm/fsgsbase.h | 4 ++--
 arch/x86/kernel/process_64.c    | 8 ++++----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h
index d552646411a9..35cff5f2becf 100644
--- a/arch/x86/include/asm/fsgsbase.h
+++ b/arch/x86/include/asm/fsgsbase.h
@@ -57,7 +57,7 @@ static inline unsigned long x86_fsbase_read_cpu(void)
 {
 	unsigned long fsbase;
 
-	if (static_cpu_has(X86_FEATURE_FSGSBASE))
+	if (boot_cpu_has(X86_FEATURE_FSGSBASE))
 		fsbase = rdfsbase();
 	else
 		rdmsrl(MSR_FS_BASE, fsbase);
@@ -67,7 +67,7 @@ static inline unsigned long x86_fsbase_read_cpu(void)
 
 static inline void x86_fsbase_write_cpu(unsigned long fsbase)
 {
-	if (static_cpu_has(X86_FEATURE_FSGSBASE))
+	if (boot_cpu_has(X86_FEATURE_FSGSBASE))
 		wrfsbase(fsbase);
 	else
 		wrmsrl(MSR_FS_BASE, fsbase);
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 9afefe325acb..df342bedea88 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -407,7 +407,7 @@ unsigned long x86_gsbase_read_cpu_inactive(void)
 {
 	unsigned long gsbase;
 
-	if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
+	if (boot_cpu_has(X86_FEATURE_FSGSBASE)) {
 		unsigned long flags;
 
 		local_irq_save(flags);
@@ -422,7 +422,7 @@ unsigned long x86_gsbase_read_cpu_inactive(void)
 
 void x86_gsbase_write_cpu_inactive(unsigned long gsbase)
 {
-	if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
+	if (boot_cpu_has(X86_FEATURE_FSGSBASE)) {
 		unsigned long flags;
 
 		local_irq_save(flags);
@@ -439,7 +439,7 @@ unsigned long x86_fsbase_read_task(struct task_struct *task)
 
 	if (task == current)
 		fsbase = x86_fsbase_read_cpu();
-	else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
+	else if (boot_cpu_has(X86_FEATURE_FSGSBASE) ||
 		 (task->thread.fsindex == 0))
 		fsbase = task->thread.fsbase;
 	else
@@ -454,7 +454,7 @@ unsigned long x86_gsbase_read_task(struct task_struct *task)
 
 	if (task == current)
 		gsbase = x86_gsbase_read_cpu_inactive();
-	else if (static_cpu_has(X86_FEATURE_FSGSBASE) ||
+	else if (boot_cpu_has(X86_FEATURE_FSGSBASE) ||
 		 (task->thread.gsindex == 0))
 		gsbase = task->thread.gsbase;
 	else
-- 
2.21.0