x86/asm/tsc: Inline native_read_tsc() and remove __native_read_tsc()

In the following commit:

  cdc7957d1954 ("x86: move native_read_tsc() offline")

... native_read_tsc() was moved out of line, presumably for some
now-obsolete vDSO-related reason. Undo it.

The entire rdtsc, shl, or sequence is only 11 bytes, and calls
via rdtscl() and similar helpers were already inlined.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/d05ffe2aaf8468ca475ebc00efad7b2fa174af19.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/entry/vdso/vclock_gettime.c

@@ -186,7 +186,7 @@ notrace static cycle_t vread_tsc(void)
 	 * but no one has ever seen it happen.
 	 */
 	rdtsc_barrier();
-	ret = (cycle_t)__native_read_tsc();
+	ret = (cycle_t)native_read_tsc();
 
 	last = gtod->cycle_last;
 

arch/x86/include/asm/msr.h

@@ -106,12 +106,10 @@ notrace static inline int native_write_msr_safe(unsigned int msr,
 	return err;
 }
 
-extern unsigned long long native_read_tsc(void);
-
 extern int rdmsr_safe_regs(u32 regs[8]);
 extern int wrmsr_safe_regs(u32 regs[8]);
 
-static __always_inline unsigned long long __native_read_tsc(void)
+static __always_inline unsigned long long native_read_tsc(void)
 {
 	DECLARE_ARGS(val, low, high);
 
@@ -181,10 +179,10 @@ static inline int rdmsrl_safe(unsigned msr, unsigned long long *p)
 }
 
 #define rdtscl(low)						\
-	((low) = (u32)__native_read_tsc())
+	((low) = (u32)native_read_tsc())
 
 #define rdtscll(val)						\
-	((val) = __native_read_tsc())
+	((val) = native_read_tsc())
 
 #define rdpmc(counter, low, high)			\
 do {							\

arch/x86/include/asm/pvclock.h

@@ -62,7 +62,7 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
 static __always_inline
 u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src)
 {
-	u64 delta = __native_read_tsc() - src->tsc_timestamp;
+	u64 delta = native_read_tsc() - src->tsc_timestamp;
 	return pvclock_scale_delta(delta, src->tsc_to_system_mul,
 				   src->tsc_shift);
 }

arch/x86/include/asm/stackprotector.h

@@ -72,7 +72,7 @@ static __always_inline void boot_init_stack_canary(void)
 	 * on during the bootup the random pool has true entropy too.
 	 */
 	get_random_bytes(&canary, sizeof(canary));
-	tsc = __native_read_tsc();
+	tsc = native_read_tsc();
 	canary += tsc + (tsc << 32UL);
 
 	current->stack_canary = canary;

arch/x86/include/asm/tsc.h

@@ -42,7 +42,7 @@ static __always_inline cycles_t vget_cycles(void)
 	if (!cpu_has_tsc)
 		return 0;
 #endif
-	return (cycles_t)__native_read_tsc();
+	return (cycles_t)native_read_tsc();
 }
 
 extern void tsc_init(void);

arch/x86/kernel/apb_timer.c

@@ -390,13 +390,13 @@ unsigned long apbt_quick_calibrate(void)
 	old = dw_apb_clocksource_read(clocksource_apbt);
 	old += loop;
 
-	t1 = __native_read_tsc();
+	t1 = native_read_tsc();
 
 	do {
 		new = dw_apb_clocksource_read(clocksource_apbt);
 	} while (new < old);
 
-	t2 = __native_read_tsc();
+	t2 = native_read_tsc();
 
 	shift = 5;
 	if (unlikely(loop >> shift == 0)) {

arch/x86/kernel/tsc.c

@@ -308,12 +308,6 @@ unsigned long long
 sched_clock(void) __attribute__((alias("native_sched_clock")));
 #endif
 
-unsigned long long native_read_tsc(void)
-{
-	return __native_read_tsc();
-}
-EXPORT_SYMBOL(native_read_tsc);
-
 int check_tsc_unstable(void)
 {
 	return tsc_unstable;