linux-kernel - [RFC 2/3] x86: Switch all C consumers of kernel_stack to this_cpu

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Date:	Thu, 26 Feb 2015 16:07:50 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	x86@...nel.org, linux-kernel@...r.kernel.org
Cc:	Borislav Petkov <bp@...en8.de>, Oleg Nesterov <oleg@...hat.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: [RFC 2/3] x86: Switch all C consumers of kernel_stack to this_cpu_sp0

This will make modifying the semantics of kernel_stack easier.

Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>
Signed-off-by: Andy Lutomirski <luto@...capital.net>
---
 arch/x86/include/asm/thread_info.h | 3 +--
 arch/x86/kernel/traps.c            | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index e82e95abc92b..92549053d86d 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -163,8 +163,7 @@ DECLARE_PER_CPU(unsigned long, kernel_stack);
 static inline struct thread_info *current_thread_info(void)
 {
 	struct thread_info *ti;
-	ti = (void *)(this_cpu_read_stable(kernel_stack) +
-		      KERNEL_STACK_OFFSET - THREAD_SIZE);
+	ti = (void *)(this_cpu_sp0() - THREAD_SIZE);
 	return ti;
 }
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index c74f2f5652da..d287ea779728 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -174,7 +174,7 @@ void ist_begin_non_atomic(struct pt_regs *regs)
 	 * will catch asm bugs and any attempt to use ist_preempt_enable
 	 * from double_fault.
 	 */
-	BUG_ON(((current_stack_pointer() ^ this_cpu_read_stable(kernel_stack))
+	BUG_ON(((current_stack_pointer() ^ (this_cpu_sp0() - 1))
 		& ~(THREAD_SIZE - 1)) != 0);
 
 	preempt_count_sub(HARDIRQ_OFFSET);
-- 
2.1.0

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