linux-kernel - [PATCH] x86/asm/msr: Make wrmsrl() a function

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Date:	Thu, 23 Jul 2015 11:55:42 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	X86 ML <x86@...nel.org>, linux-kernel@...r.kernel.org
Cc:	Brian Gerst <brgerst@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>, Willy Tarreau <w@....eu>,
	Borislav Petkov <bp@...en8.de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH] x86/asm/msr: Make wrmsrl() a function

As of cf991de2f614 ("x86/asm/msr: Make wrmsrl_safe() a function"),
wrmsrl_safe is a function, but wrmsrl is still a macro.  The wrmsrl
macro performs invalid shifts if the value argument is 32 bits.
This makes it unnecessarily awkward to write code that puts an
unsigned long into an MSR.

To make this work, syscall_init needs tweaking to stop passing
a function pointer to wrmsrl.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---

Spotted while fiddling with enable_sep_cpu().

 arch/x86/include/asm/msr.h      | 6 ++++--
 arch/x86/include/asm/paravirt.h | 6 +++++-
 arch/x86/kernel/cpu/common.c    | 4 ++--
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h
index 131eec2ca137..714c80755dae 100644
--- a/arch/x86/include/asm/msr.h
+++ b/arch/x86/include/asm/msr.h
@@ -185,8 +185,10 @@ static inline void wrmsr(unsigned msr, unsigned low, unsigned high)
 #define rdmsrl(msr, val)			\
 	((val) = native_read_msr((msr)))
 
-#define wrmsrl(msr, val)						\
-	native_write_msr((msr), (u32)((u64)(val)), (u32)((u64)(val) >> 32))
+static inline void wrmsrl(unsigned msr, u64 val)
+{
+	native_write_msr(msr, (u32)val, (u32)(val >> 32));
+}
 
 /* wrmsr with exception handling */
 static inline int wrmsr_safe(unsigned msr, unsigned low, unsigned high)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index c2be0375bcad..10d0596433f8 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -153,7 +153,11 @@ do {						\
 	val = paravirt_read_msr(msr, &_err);	\
 } while (0)
 
-#define wrmsrl(msr, val)	wrmsr(msr, (u32)((u64)(val)), ((u64)(val))>>32)
+static inline void wrmsrl(unsigned msr, u64 val)
+{
+	wrmsr(msr, (u32)val, (u32)(val>>32));
+}
+
 #define wrmsr_safe(msr, a, b)	paravirt_write_msr(msr, a, b)
 
 /* rdmsr with exception handling */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index ffb0020ada5f..d27ab6e5e671 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1184,10 +1184,10 @@ void syscall_init(void)
 	 * set CS/DS but only a 32bit target. LSTAR sets the 64bit rip.
 	 */
 	wrmsrl(MSR_STAR,  ((u64)__USER32_CS)<<48  | ((u64)__KERNEL_CS)<<32);
-	wrmsrl(MSR_LSTAR, entry_SYSCALL_64);
+	wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);
 
 #ifdef CONFIG_IA32_EMULATION
-	wrmsrl(MSR_CSTAR, entry_SYSCALL_compat);
+	wrmsrl(MSR_CSTAR, (unsigned long)entry_SYSCALL_compat);
 	enable_sep_cpu();
 #else
 	wrmsrl(MSR_CSTAR, ignore_sysret);
-- 
2.4.3

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