linux-kernel - [PATCH v4 20/29] x86/smp: Remove stack_smp_processor

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Message-Id: <6c8610ea4d224d14699f62c07e569e2f01499234.1466974736.git.luto@kernel.org>
Date:	Sun, 26 Jun 2016 14:55:42 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Jann Horn <jann@...jh.net>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v4 20/29] x86/smp: Remove stack_smp_processor_id()

It serves no purpose -- raw_smp_processor_id() works fine.  This
change will be needed to move thread_info off the stack.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/include/asm/cpu.h   | 1 -
 arch/x86/include/asm/smp.h   | 6 ------
 arch/x86/kernel/cpu/common.c | 2 +-
 3 files changed, 1 insertion(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index 678637ad7476..59d34c521d96 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -17,7 +17,6 @@ static inline void prefill_possible_map(void) {}
 
 #define cpu_physical_id(cpu)			boot_cpu_physical_apicid
 #define safe_smp_processor_id()			0
-#define stack_smp_processor_id()		0
 
 #endif /* CONFIG_SMP */
 
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 66b057306f40..0576b6157f3a 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -172,12 +172,6 @@ extern int safe_smp_processor_id(void);
 #elif defined(CONFIG_X86_64_SMP)
 #define raw_smp_processor_id() (this_cpu_read(cpu_number))
 
-#define stack_smp_processor_id()					\
-({								\
-	struct thread_info *ti;						\
-	__asm__("andq %%rsp,%0; ":"=r" (ti) : "0" (CURRENT_MASK));	\
-	ti->cpu;							\
-})
 #define safe_smp_processor_id()		smp_processor_id()
 
 #endif
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0fe6953f421c..d22a7b9c4f0e 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1452,7 +1452,7 @@ void cpu_init(void)
 	struct task_struct *me;
 	struct tss_struct *t;
 	unsigned long v;
-	int cpu = stack_smp_processor_id();
+	int cpu = raw_smp_processor_id();
 	int i;
 
 	wait_for_master_cpu(cpu);
-- 
2.7.4