x86-64: Move vread_tsc and vread_hpet into the vDSO

The vsyscall page now consists entirely of trap instructions.

Cc: John Stultz <johnstul@us.ibm.com>
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Link: http://lkml.kernel.org/r/637648f303f2ef93af93bae25186e9a1bea093f5.1310639973.git.luto@mit.edu
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/arch/x86/include/asm/clocksource.h b/arch/x86/include/asm/clocksource.h
index a5df33f..3882c65 100644 (file)
--- a/arch/x86/include/asm/clocksource.h
+++ b/arch/x86/include/asm/clocksource.h
@@ -7,8 +7,12 @@
 
 #define __ARCH_HAS_CLOCKSOURCE_DATA
 
+#define VCLOCK_NONE 0  /* No vDSO clock available.     */
+#define VCLOCK_TSC  1  /* vDSO should use vread_tsc.   */
+#define VCLOCK_HPET 2  /* vDSO should use vread_hpet.  */
+
 struct arch_clocksource_data {
-       cycle_t (*vread)(void);
+       int vclock_mode;
 };
 
 #endif /* CONFIG_X86_64 */

diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 9db5583..83e2efd 100644 (file)
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -51,10 +51,6 @@ extern int unsynchronized_tsc(void);
 extern int check_tsc_unstable(void);
 extern unsigned long native_calibrate_tsc(void);
 
-#ifdef CONFIG_X86_64
-extern cycles_t vread_tsc(void);
-#endif
-
 /*
  * Boot-time check whether the TSCs are synchronized across
  * all CPUs/cores:

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index aa5add8..815285b 100644 (file)
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -13,7 +13,7 @@ struct vsyscall_gtod_data {
 
        struct timezone sys_tz;
        struct { /* extract of a clocksource struct */
-               cycle_t (*vread)(void);
+               int vclock_mode;
                cycle_t cycle_last;
                cycle_t mask;
                u32     mult;

diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index d555973..6010707 100644 (file)
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -16,10 +16,6 @@ enum vsyscall_num {
 #ifdef __KERNEL__
 #include <linux/seqlock.h>
 
-/* Definitions for CONFIG_GENERIC_TIME definitions */
-#define __vsyscall_fn \
-       __attribute__ ((unused, __section__(".vsyscall_fn"))) notrace
-
 #define VGETCPU_RDTSCP 1
 #define VGETCPU_LSL    2
 

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index cc0469a..2deef3d 100644 (file)
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -24,17 +24,12 @@ endif
 nostackp := $(call cc-option, -fno-stack-protector)
 CFLAGS_vsyscall_64.o   := $(PROFILING) -g0 $(nostackp)
 CFLAGS_hpet.o          := $(nostackp)
-CFLAGS_vread_tsc_64.o  := $(nostackp)
 CFLAGS_paravirt.o      := $(nostackp)
 GCOV_PROFILE_vsyscall_64.o     := n
 GCOV_PROFILE_hpet.o            := n
 GCOV_PROFILE_tsc.o             := n
-GCOV_PROFILE_vread_tsc_64.o    := n
 GCOV_PROFILE_paravirt.o                := n
 
-# vread_tsc_64 is hot and should be fully optimized:
-CFLAGS_REMOVE_vread_tsc_64.o = -pg -fno-optimize-sibling-calls
-
 obj-y                  := process_$(BITS).o signal.o entry_$(BITS).o
 obj-y                  += traps.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
 obj-y                  += time.o ioport.o ldt.o dumpstack.o
@@ -43,7 +38,7 @@ obj-$(CONFIG_IRQ_WORK)  += irq_work.o
 obj-y                  += probe_roms.o
 obj-$(CONFIG_X86_32)   += sys_i386_32.o i386_ksyms_32.o
 obj-$(CONFIG_X86_64)   += sys_x86_64.o x8664_ksyms_64.o
-obj-$(CONFIG_X86_64)   += syscall_64.o vsyscall_64.o vread_tsc_64.o
+obj-$(CONFIG_X86_64)   += syscall_64.o vsyscall_64.o
 obj-$(CONFIG_X86_64)   += vsyscall_emu_64.o
 obj-y                  += bootflag.o e820.o
 obj-y                  += pci-dma.o quirks.o topology.o kdebugfs.o

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index ddb207b..c638228 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -14,7 +14,6 @@
 #include <asm/pgtable.h>
 #include <asm/mce.h>
 #include <asm/nmi.h>
-#include <asm/vsyscall.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 #include <asm/io.h>
@@ -250,7 +249,6 @@ static void __init_or_module add_nops(void *insns, unsigned int len)
 
 extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
 extern s32 __smp_locks[], __smp_locks_end[];
-extern char __vsyscall_0;
 void *text_poke_early(void *addr, const void *opcode, size_t len);
 
 /* Replace instructions with better alternatives for this CPU type.
@@ -294,12 +292,6 @@ void __init_or_module apply_alternatives(struct alt_instr *start,
                add_nops(insnbuf + a->replacementlen,
                         a->instrlen - a->replacementlen);
 
-#ifdef CONFIG_X86_64
-               /* vsyscall code is not mapped yet. resolve it manually. */
-               if (instr >= (u8 *)VSYSCALL_START && instr < (u8*)VSYSCALL_END) {
-                       instr = __va(instr - (u8*)VSYSCALL_START + (u8*)__pa_symbol(&__vsyscall_0));
-               }
-#endif
                text_poke_early(instr, insnbuf, a->instrlen);
        }
 }

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 0e07257..d10cc00 100644 (file)
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -738,13 +738,6 @@ static cycle_t read_hpet(struct clocksource *cs)
        return (cycle_t)hpet_readl(HPET_COUNTER);
 }
 
-#ifdef CONFIG_X86_64
-static cycle_t __vsyscall_fn vread_hpet(void)
-{
-       return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + 0xf0);
-}
-#endif
-
 static struct clocksource clocksource_hpet = {
        .name           = "hpet",
        .rating         = 250,
@@ -753,7 +746,7 @@ static struct clocksource clocksource_hpet = {
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
        .resume         = hpet_resume_counter,
 #ifdef CONFIG_X86_64
-       .archdata       = { .vread = vread_hpet },
+       .archdata       = { .vclock_mode = VCLOCK_HPET },
 #endif
 };
 

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index e7a74b8..56c633a 100644 (file)
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -777,7 +777,7 @@ static struct clocksource clocksource_tsc = {
        .flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
                                  CLOCK_SOURCE_MUST_VERIFY,
 #ifdef CONFIG_X86_64
-       .archdata               = { .vread = vread_tsc },
+       .archdata               = { .vclock_mode = VCLOCK_TSC },
 #endif
 };
 

diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 8017471..4aa9c54 100644 (file)
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -169,9 +169,6 @@ SECTIONS
        .vsyscall : AT(VLOAD(.vsyscall)) {
                *(.vsyscall_0)
 
-               . = ALIGN(L1_CACHE_BYTES);
-               *(.vsyscall_fn)
-
                . = 1024;
                *(.vsyscall_1)
 

diff --git a/arch/x86/kernel/vread_tsc_64.c b/arch/x86/kernel/vread_tsc_64.c
deleted file mode 100644 (file)
index a81aa9e..0000000
--- a/arch/x86/kernel/vread_tsc_64.c
+++ /dev/null
@@ -1,36 +0,0 @@
-/* This code runs in userspace. */
-
-#define DISABLE_BRANCH_PROFILING
-#include <asm/vgtod.h>
-
-notrace cycle_t __vsyscall_fn vread_tsc(void)
-{
-       cycle_t ret;
-       u64 last;
-
-       /*
-        * Empirically, a fence (of type that depends on the CPU)
-        * before rdtsc is enough to ensure that rdtsc is ordered
-        * with respect to loads.  The various CPU manuals are unclear
-        * as to whether rdtsc can be reordered with later loads,
-        * but no one has ever seen it happen.
-        */
-       rdtsc_barrier();
-       ret = (cycle_t)vget_cycles();
-
-       last = VVAR(vsyscall_gtod_data).clock.cycle_last;
-
-       if (likely(ret >= last))
-               return ret;
-
-       /*
-        * GCC likes to generate cmov here, but this branch is extremely
-        * predictable (it's just a funciton of time and the likely is
-        * very likely) and there's a data dependence, so force GCC
-        * to generate a branch instead.  I don't barrier() because
-        * we don't actually need a barrier, and if this function
-        * ever gets inlined it will generate worse code.
-        */
-       asm volatile ("");
-       return last;
-}

diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 12d488f..dda7dff 100644 (file)
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -74,7 +74,7 @@ void update_vsyscall(struct timespec *wall_time, struct timespec *wtm,
        write_seqlock_irqsave(&vsyscall_gtod_data.lock, flags);
 
        /* copy vsyscall data */
-       vsyscall_gtod_data.clock.vread          = clock->archdata.vread;
+       vsyscall_gtod_data.clock.vclock_mode    = clock->archdata.vclock_mode;
        vsyscall_gtod_data.clock.cycle_last     = clock->cycle_last;
        vsyscall_gtod_data.clock.mask           = clock->mask;
        vsyscall_gtod_data.clock.mult           = mult;

diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index cf54813..8792d6e 100644 (file)
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -17,6 +17,7 @@
 #include <linux/time.h>
 #include <linux/string.h>
 #include <asm/vsyscall.h>
+#include <asm/fixmap.h>
 #include <asm/vgtod.h>
 #include <asm/timex.h>
 #include <asm/hpet.h>
@@ -25,6 +26,43 @@
 
 #define gtod (&VVAR(vsyscall_gtod_data))
 
+notrace static cycle_t vread_tsc(void)
+{
+       cycle_t ret;
+       u64 last;
+
+       /*
+        * Empirically, a fence (of type that depends on the CPU)
+        * before rdtsc is enough to ensure that rdtsc is ordered
+        * with respect to loads.  The various CPU manuals are unclear
+        * as to whether rdtsc can be reordered with later loads,
+        * but no one has ever seen it happen.
+        */
+       rdtsc_barrier();
+       ret = (cycle_t)vget_cycles();
+
+       last = VVAR(vsyscall_gtod_data).clock.cycle_last;
+
+       if (likely(ret >= last))
+               return ret;
+
+       /*
+        * GCC likes to generate cmov here, but this branch is extremely
+        * predictable (it's just a funciton of time and the likely is
+        * very likely) and there's a data dependence, so force GCC
+        * to generate a branch instead.  I don't barrier() because
+        * we don't actually need a barrier, and if this function
+        * ever gets inlined it will generate worse code.
+        */
+       asm volatile ("");
+       return last;
+}
+
+static notrace cycle_t vread_hpet(void)
+{
+       return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + 0xf0);
+}
+
 notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
 {
        long ret;
@@ -36,9 +74,12 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
 notrace static inline long vgetns(void)
 {
        long v;
-       cycles_t (*vread)(void);
-       vread = gtod->clock.vread;
-       v = (vread() - gtod->clock.cycle_last) & gtod->clock.mask;
+       cycles_t cycles;
+       if (gtod->clock.vclock_mode == VCLOCK_TSC)
+               cycles = vread_tsc();
+       else
+               cycles = vread_hpet();
+       v = (cycles - gtod->clock.cycle_last) & gtod->clock.mask;
        return (v * gtod->clock.mult) >> gtod->clock.shift;
 }
 
@@ -118,11 +159,11 @@ notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
 {
        switch (clock) {
        case CLOCK_REALTIME:
-               if (likely(gtod->clock.vread))
+               if (likely(gtod->clock.vclock_mode != VCLOCK_NONE))
                        return do_realtime(ts);
                break;
        case CLOCK_MONOTONIC:
-               if (likely(gtod->clock.vread))
+               if (likely(gtod->clock.vclock_mode != VCLOCK_NONE))
                        return do_monotonic(ts);
                break;
        case CLOCK_REALTIME_COARSE:
@@ -139,7 +180,7 @@ int clock_gettime(clockid_t, struct timespec *)
 notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
        long ret;
-       if (likely(gtod->clock.vread)) {
+       if (likely(gtod->clock.vclock_mode != VCLOCK_NONE)) {
                if (likely(tv != NULL)) {
                        BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
                                     offsetof(struct timespec, tv_nsec) ||