Use VDSO for clock_gettime(2) and gettimeofday(2).
Bug: 15387103
Change-Id: Ifc3608ea65060c1dc38120b10b6e79874f182a36
diff --git a/benchmarks/Android.mk b/benchmarks/Android.mk
index f9722ae..4d7ad96 100644
--- a/benchmarks/Android.mk
+++ b/benchmarks/Android.mk
@@ -54,7 +54,7 @@
LOCAL_SRC_FILES := $(benchmark_src_files)
include $(BUILD_EXECUTABLE)
-ifeq ($(HOST_OS)-$(HOST_ARCH),linux-x86)
+ifeq ($(HOST_OS)-$(HOST_ARCH),$(filter $(HOST_OS)-$(HOST_ARCH),linux-x86 linux-x86_64))
ifeq ($(TARGET_ARCH),x86)
LINKER = linker
NATIVE_SUFFIX=32
diff --git a/benchmarks/time_benchmark.cpp b/benchmarks/time_benchmark.cpp
index 3bf8c07..0a146ae 100644
--- a/benchmarks/time_benchmark.cpp
+++ b/benchmarks/time_benchmark.cpp
@@ -16,6 +16,7 @@
#include "benchmark.h"
+#include <sys/syscall.h>
#include <time.h>
#if defined(__BIONIC__)
@@ -41,7 +42,7 @@
static void BM_time_clock_gettime(int iters) {
StartBenchmarkTiming();
- struct timespec t;
+ timespec t;
for (int i = 0; i < iters; ++i) {
clock_gettime(CLOCK_MONOTONIC, &t);
}
@@ -49,3 +50,50 @@
StopBenchmarkTiming();
}
BENCHMARK(BM_time_clock_gettime);
+
+static void BM_time_clock_gettime_syscall(int iters) {
+ StartBenchmarkTiming();
+
+ timespec t;
+ for (int i = 0; i < iters; ++i) {
+ syscall(__NR_clock_gettime, CLOCK_MONOTONIC, &t);
+ }
+
+ StopBenchmarkTiming();
+}
+BENCHMARK(BM_time_clock_gettime_syscall);
+
+static void BM_time_gettimeofday(int iters) {
+ StartBenchmarkTiming();
+
+ timeval tv;
+ for (int i = 0; i < iters; ++i) {
+ gettimeofday(&tv, NULL);
+ }
+
+ StopBenchmarkTiming();
+}
+BENCHMARK(BM_time_gettimeofday);
+
+static void BM_time_gettimeofday_syscall(int iters) {
+ StartBenchmarkTiming();
+
+ timeval tv;
+ for (int i = 0; i < iters; ++i) {
+ syscall(__NR_gettimeofday, &tv, NULL);
+ }
+
+ StopBenchmarkTiming();
+}
+BENCHMARK(BM_time_gettimeofday_syscall);
+
+static void BM_time_time(int iters) {
+ StartBenchmarkTiming();
+
+ for (int i = 0; i < iters; ++i) {
+ time(NULL);
+ }
+
+ StopBenchmarkTiming();
+}
+BENCHMARK(BM_time_time);
diff --git a/libc/Android.mk b/libc/Android.mk
index 51002e5..0485d72 100644
--- a/libc/Android.mk
+++ b/libc/Android.mk
@@ -229,6 +229,7 @@
bionic/umount.cpp \
bionic/unlink.cpp \
bionic/utimes.cpp \
+ bionic/vdso.cpp \
bionic/vfork.cpp \
bionic/wait.cpp \
bionic/wchar.cpp \
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index b4c8134..7ae054e 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -194,11 +194,9 @@
int swapoff(const char*) all
# time
-int gettimeofday(struct timeval*, struct timezone*) all
int settimeofday(const struct timeval*, const struct timezone*) all
clock_t times(struct tms*) all
int nanosleep(const struct timespec*, struct timespec*) all
-int clock_gettime(clockid_t clk_id, struct timespec* tp) all
int clock_settime(clockid_t clk_id, const struct timespec* tp) all
int clock_getres(clockid_t clk_id, struct timespec* res) all
int clock_nanosleep(clockid_t clock_id, int flags, const struct timespec* req, struct timespec* rem) all
@@ -320,3 +318,9 @@
# x86-specific
int __set_thread_area:set_thread_area(void*) x86
+
+# vdso stuff.
+int clock_gettime(clockid_t, timespec*) arm,mips,mips64,x86
+int __clock_gettime:clock_gettime(clockid_t, timespec*) arm64,x86_64
+int gettimeofday(timeval*, timezone*) arm,mips,mips64,x86
+int __gettimeofday:gettimeofday(timeval*, timezone*) arm64,x86_64
diff --git a/libc/arch-arm64/syscalls/clock_gettime.S b/libc/arch-arm64/syscalls/__clock_gettime.S
similarity index 76%
rename from libc/arch-arm64/syscalls/clock_gettime.S
rename to libc/arch-arm64/syscalls/__clock_gettime.S
index ffdde57..f346648 100644
--- a/libc/arch-arm64/syscalls/clock_gettime.S
+++ b/libc/arch-arm64/syscalls/__clock_gettime.S
@@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
-ENTRY(clock_gettime)
+ENTRY(__clock_gettime)
mov x8, __NR_clock_gettime
svc #0
@@ -11,4 +11,5 @@
b.hi __set_errno
ret
-END(clock_gettime)
+END(__clock_gettime)
+.hidden __clock_gettime
diff --git a/libc/arch-arm64/syscalls/gettimeofday.S b/libc/arch-arm64/syscalls/__gettimeofday.S
similarity index 77%
rename from libc/arch-arm64/syscalls/gettimeofday.S
rename to libc/arch-arm64/syscalls/__gettimeofday.S
index 3b6104b..6582c49 100644
--- a/libc/arch-arm64/syscalls/gettimeofday.S
+++ b/libc/arch-arm64/syscalls/__gettimeofday.S
@@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
-ENTRY(gettimeofday)
+ENTRY(__gettimeofday)
mov x8, __NR_gettimeofday
svc #0
@@ -11,4 +11,5 @@
b.hi __set_errno
ret
-END(gettimeofday)
+END(__gettimeofday)
+.hidden __gettimeofday
diff --git a/libc/arch-x86_64/syscalls/clock_gettime.S b/libc/arch-x86_64/syscalls/__clock_gettime.S
similarity index 78%
rename from libc/arch-x86_64/syscalls/clock_gettime.S
rename to libc/arch-x86_64/syscalls/__clock_gettime.S
index 20850c8..7e553b8 100644
--- a/libc/arch-x86_64/syscalls/clock_gettime.S
+++ b/libc/arch-x86_64/syscalls/__clock_gettime.S
@@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
-ENTRY(clock_gettime)
+ENTRY(__clock_gettime)
movl $__NR_clock_gettime, %eax
syscall
cmpq $-MAX_ERRNO, %rax
@@ -12,4 +12,5 @@
call __set_errno
1:
ret
-END(clock_gettime)
+END(__clock_gettime)
+.hidden __clock_gettime
diff --git a/libc/arch-x86_64/syscalls/gettimeofday.S b/libc/arch-x86_64/syscalls/__gettimeofday.S
similarity index 79%
rename from libc/arch-x86_64/syscalls/gettimeofday.S
rename to libc/arch-x86_64/syscalls/__gettimeofday.S
index 4867c30..a38eb64 100644
--- a/libc/arch-x86_64/syscalls/gettimeofday.S
+++ b/libc/arch-x86_64/syscalls/__gettimeofday.S
@@ -2,7 +2,7 @@
#include <private/bionic_asm.h>
-ENTRY(gettimeofday)
+ENTRY(__gettimeofday)
movl $__NR_gettimeofday, %eax
syscall
cmpq $-MAX_ERRNO, %rax
@@ -12,4 +12,5 @@
call __set_errno
1:
ret
-END(gettimeofday)
+END(__gettimeofday)
+.hidden __gettimeofday
diff --git a/libc/bionic/dl_iterate_phdr_static.cpp b/libc/bionic/dl_iterate_phdr_static.cpp
index 7e9eedd..155a7a0 100644
--- a/libc/bionic/dl_iterate_phdr_static.cpp
+++ b/libc/bionic/dl_iterate_phdr_static.cpp
@@ -27,6 +27,7 @@
*/
#include <elf.h>
+#include <string.h>
#include <sys/auxv.h>
#include <sys/types.h>
#include <link.h>
@@ -37,11 +38,9 @@
int dl_iterate_phdr(int (*cb)(struct dl_phdr_info* info, size_t size, void* data), void* data) {
ElfW(Ehdr)* ehdr = reinterpret_cast<ElfW(Ehdr)*>(&__executable_start);
- // TODO: again, copied from linker.c. Find a better home for this later.
- if (ehdr->e_ident[EI_MAG0] != ELFMAG0) return -1;
- if (ehdr->e_ident[EI_MAG1] != ELFMAG1) return -1;
- if (ehdr->e_ident[EI_MAG2] != ELFMAG2) return -1;
- if (ehdr->e_ident[EI_MAG3] != ELFMAG3) return -1;
+ if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0) {
+ return -1;
+ }
// Dynamic binaries get their dl_iterate_phdr from the dynamic linker, but
// static binaries get this. We don't have a list of shared objects to
@@ -54,7 +53,7 @@
exe_info.dlpi_phdr = reinterpret_cast<ElfW(Phdr)*>(reinterpret_cast<uintptr_t>(ehdr) + ehdr->e_phoff);
exe_info.dlpi_phnum = ehdr->e_phnum;
-#ifdef AT_SYSINFO_EHDR
+#if defined(AT_SYSINFO_EHDR)
// Try the executable first.
int rc = cb(&exe_info, sizeof(exe_info), data);
if (rc != 0) {
diff --git a/libc/bionic/libc_init_common.cpp b/libc/bionic/libc_init_common.cpp
index aa76650..9e4eecd 100644
--- a/libc/bionic/libc_init_common.cpp
+++ b/libc/bionic/libc_init_common.cpp
@@ -51,6 +51,8 @@
extern "C" int __set_tls(void* ptr);
extern "C" int __set_tid_address(int* tid_address);
+void __libc_init_vdso();
+
// Not public, but well-known in the BSDs.
const char* __progname;
@@ -129,6 +131,8 @@
_pthread_internal_add(main_thread);
__system_properties_init(); // Requires 'environ'.
+
+ __libc_init_vdso();
}
/* This function will be called during normal program termination
diff --git a/libc/bionic/vdso.cpp b/libc/bionic/vdso.cpp
new file mode 100644
index 0000000..0875ee6
--- /dev/null
+++ b/libc/bionic/vdso.cpp
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <link.h>
+#include <sys/auxv.h>
+#include <unistd.h>
+
+// x86 has a vdso, but there's nothing useful to us in it.
+#if defined(__aarch64__) || defined(__x86_64__)
+
+#if defined(__aarch64__)
+#define VDSO_CLOCK_GETTIME_SYMBOL "__kernel_clock_gettime"
+#define VDSO_GETTIMEOFDAY_SYMBOL "__kernel_gettimeofday"
+#elif defined(__x86_64__)
+#define VDSO_CLOCK_GETTIME_SYMBOL "__vdso_clock_gettime"
+#define VDSO_GETTIMEOFDAY_SYMBOL "__vdso_gettimeofday"
+#endif
+
+#include <time.h>
+
+extern "C" int __clock_gettime(int, timespec*);
+extern "C" int __gettimeofday(timeval*, struct timezone*);
+
+struct vdso_entry {
+ const char* name;
+ void* fn;
+};
+
+enum {
+ VDSO_CLOCK_GETTIME = 0,
+ VDSO_GETTIMEOFDAY,
+ VDSO_END
+};
+
+static vdso_entry vdso_entries[] = {
+ [VDSO_CLOCK_GETTIME] = { VDSO_CLOCK_GETTIME_SYMBOL, reinterpret_cast<void*>(__clock_gettime) },
+ [VDSO_GETTIMEOFDAY] = { VDSO_GETTIMEOFDAY_SYMBOL, reinterpret_cast<void*>(__gettimeofday) },
+};
+
+int clock_gettime(int clock_id, timespec* tp) {
+ static int (*vdso_clock_gettime)(int, timespec*) =
+ (int (*)(int, timespec*)) vdso_entries[VDSO_CLOCK_GETTIME].fn;
+ return vdso_clock_gettime(clock_id, tp);
+}
+
+int gettimeofday(timeval* tv, struct timezone* tz) {
+ static int (*vdso_gettimeofday)(timeval*, struct timezone*) =
+ (int (*)(timeval*, struct timezone*)) vdso_entries[VDSO_GETTIMEOFDAY].fn;
+ return vdso_gettimeofday(tv, tz);
+}
+
+void __libc_init_vdso() {
+ // Do we have a vdso?
+ uintptr_t vdso_ehdr_addr = getauxval(AT_SYSINFO_EHDR);
+ ElfW(Ehdr)* vdso_ehdr = reinterpret_cast<ElfW(Ehdr)*>(vdso_ehdr_addr);
+ if (vdso_ehdr == NULL) {
+ return;
+ }
+
+ // How many symbols does it have?
+ size_t symbol_count = 0;
+ ElfW(Shdr)* vdso_shdr = reinterpret_cast<ElfW(Shdr)*>(vdso_ehdr_addr + vdso_ehdr->e_shoff);
+ for (size_t i = 0; i < vdso_ehdr->e_shnum; ++i) {
+ if (vdso_shdr[i].sh_type == SHT_DYNSYM) {
+ symbol_count = vdso_shdr[i].sh_size / sizeof(ElfW(Sym));
+ }
+ }
+ if (symbol_count == 0) {
+ return;
+ }
+
+ // Where's the dynamic table?
+ ElfW(Addr) vdso_addr = 0;
+ ElfW(Dyn)* vdso_dyn = NULL;
+ ElfW(Phdr)* vdso_phdr = reinterpret_cast<ElfW(Phdr)*>(vdso_ehdr_addr + vdso_ehdr->e_phoff);
+ for (size_t i = 0; i < vdso_ehdr->e_phnum; ++i) {
+ if (vdso_phdr[i].p_type == PT_DYNAMIC) {
+ vdso_dyn = reinterpret_cast<ElfW(Dyn)*>(vdso_ehdr_addr + vdso_phdr[i].p_offset);
+ } else if (vdso_phdr[i].p_type == PT_LOAD) {
+ vdso_addr = vdso_ehdr_addr + vdso_phdr[i].p_offset - vdso_phdr[i].p_vaddr;
+ }
+ }
+ if (vdso_addr == 0 || vdso_dyn == NULL) {
+ return;
+ }
+
+ // Where are the string and symbol tables?
+ const char* strtab = NULL;
+ ElfW(Sym)* symtab = NULL;
+ for (ElfW(Dyn)* d = vdso_dyn; d->d_tag != DT_NULL; ++d) {
+ if (d->d_tag == DT_STRTAB) {
+ strtab = reinterpret_cast<const char*>(vdso_addr + d->d_un.d_ptr);
+ } else if (d->d_tag == DT_SYMTAB) {
+ symtab = reinterpret_cast<ElfW(Sym)*>(vdso_addr + d->d_un.d_ptr);
+ }
+ }
+ if (strtab == NULL || symtab == NULL) {
+ return;
+ }
+
+ // Are there any symbols we want?
+ for (size_t i = 0; i < symbol_count; ++i) {
+ for (size_t j = 0; j < VDSO_END; ++j) {
+ if (strcmp(vdso_entries[j].name, strtab + symtab[i].st_name) == 0) {
+ vdso_entries[j].fn = reinterpret_cast<void*>(vdso_addr + symtab[i].st_value);
+ }
+ }
+ }
+}
+
+#else
+
+void __libc_init_vdso() {
+}
+
+#endif
diff --git a/linker/linker_phdr.cpp b/linker/linker_phdr.cpp
index 11585af..0b99d20 100644
--- a/linker/linker_phdr.cpp
+++ b/linker/linker_phdr.cpp
@@ -156,10 +156,7 @@
}
bool ElfReader::VerifyElfHeader() {
- if (header_.e_ident[EI_MAG0] != ELFMAG0 ||
- header_.e_ident[EI_MAG1] != ELFMAG1 ||
- header_.e_ident[EI_MAG2] != ELFMAG2 ||
- header_.e_ident[EI_MAG3] != ELFMAG3) {
+ if (memcmp(header_.e_ident, ELFMAG, SELFMAG) != 0) {
DL_ERR("\"%s\" has bad ELF magic", name_);
return false;
}
diff --git a/tests/sys_time_test.cpp b/tests/sys_time_test.cpp
index 730992f..bb142bc 100644
--- a/tests/sys_time_test.cpp
+++ b/tests/sys_time_test.cpp
@@ -17,6 +17,7 @@
#include <gtest/gtest.h>
#include <errno.h>
+#include <sys/syscall.h>
#include <sys/time.h>
#include "TemporaryFile.h"
@@ -46,3 +47,23 @@
TemporaryFile tf;
ASSERT_EQ(0, utimes(tf.filename, NULL));
}
+
+TEST(sys_time, gettimeofday) {
+ // Try to ensure that our vdso gettimeofday is working.
+ timeval tv1;
+ ASSERT_EQ(0, gettimeofday(&tv1, NULL));
+ timeval tv2;
+ ASSERT_EQ(0, syscall(__NR_gettimeofday, &tv2, NULL));
+
+ // What's the difference between the two?
+ tv2.tv_sec -= tv1.tv_sec;
+ tv2.tv_usec -= tv1.tv_usec;
+ if (tv2.tv_usec < 0) {
+ --tv2.tv_sec;
+ tv2.tv_usec += 1000000;
+ }
+
+ // Should be less than (a very generous, to try to avoid flakiness) 1000us.
+ ASSERT_EQ(0, tv2.tv_sec);
+ ASSERT_LT(tv2.tv_usec, 1000);
+}
diff --git a/tests/time_test.cpp b/tests/time_test.cpp
index 58cb374..12b1ea7 100644
--- a/tests/time_test.cpp
+++ b/tests/time_test.cpp
@@ -21,6 +21,7 @@
#include <gtest/gtest.h>
#include <pthread.h>
#include <signal.h>
+#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
@@ -419,3 +420,23 @@
ASSERT_EQ(ESRCH, pthread_detach(tdd.thread_id));
#endif
}
+
+TEST(time, clock_gettime) {
+ // Try to ensure that our vdso clock_gettime is working.
+ timespec ts1;
+ ASSERT_EQ(0, clock_gettime(CLOCK_MONOTONIC, &ts1));
+ timespec ts2;
+ ASSERT_EQ(0, syscall(__NR_clock_gettime, CLOCK_MONOTONIC, &ts2));
+
+ // What's the difference between the two?
+ ts2.tv_sec -= ts1.tv_sec;
+ ts2.tv_nsec -= ts1.tv_nsec;
+ if (ts2.tv_nsec < 0) {
+ --ts2.tv_sec;
+ ts2.tv_nsec += 1000000000;
+ }
+
+ // Should be less than (a very generous, to try to avoid flakiness) 1000000ns.
+ ASSERT_EQ(0, ts2.tv_sec);
+ ASSERT_LT(ts2.tv_nsec, 1000000);
+}