linux-kernel - [PATCH 039/208] x86/fpu: Add debug check to kernel_fpu

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Date:	Tue,  5 May 2015 18:24:19 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	linux-kernel@...r.kernel.org
Cc:	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 039/208] x86/fpu: Add debug check to kernel_fpu_disable()

We are not supposed to call kernel_fpu_disable() if we have not
previously enabled it.

Also use kernel_fpu_disable()/enable() in the __kernel_fpu_begin/end()
primitives, instead of writing to in_kernel_fpu directly,
so that we get the debugging checks.

Reviewed-by: Borislav Petkov <bp@...en8.de>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/fpu/core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 587e4ab46f59..bcf705751d02 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -17,6 +17,7 @@ static void kernel_fpu_disable(void)
 
 static void kernel_fpu_enable(void)
 {
+	WARN_ON_ONCE(!this_cpu_read(in_kernel_fpu));
 	this_cpu_write(in_kernel_fpu, false);
 }
 
@@ -77,7 +78,7 @@ void __kernel_fpu_begin(void)
 {
 	struct task_struct *me = current;
 
-	this_cpu_write(in_kernel_fpu, true);
+	kernel_fpu_disable();
 
 	if (__thread_has_fpu(me)) {
 		__save_init_fpu(me);
@@ -100,7 +101,7 @@ void __kernel_fpu_end(void)
 		stts();
 	}
 
-	this_cpu_write(in_kernel_fpu, false);
+	kernel_fpu_enable();
 }
 EXPORT_SYMBOL(__kernel_fpu_end);
 
-- 
2.1.0

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