[libc-commits] [libc] [libc] implement clock_gettime using vDSO (PR #108458)
Schrodinger ZHU Yifan via libc-commits
libc-commits at lists.llvm.org
Fri Sep 13 07:48:43 PDT 2024
https://github.com/SchrodingerZhu updated https://github.com/llvm/llvm-project/pull/108458
>From 8d419972fc1cb717084f51a20dd4cee22cdefadf Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Thu, 12 Sep 2024 17:55:03 -0400
Subject: [PATCH 1/2] [libc] implement clock_gettime using vDSO
---
libc/src/__support/macros/optimization.h | 7 ++++---
libc/src/__support/time/linux/CMakeLists.txt | 1 +
libc/src/__support/time/linux/clock_gettime.h | 9 +++++++++
3 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/libc/src/__support/macros/optimization.h b/libc/src/__support/macros/optimization.h
index 5ffd474d35c54d..af9954151ed88c 100644
--- a/libc/src/__support/macros/optimization.h
+++ b/libc/src/__support/macros/optimization.h
@@ -10,7 +10,7 @@
#ifndef LLVM_LIBC_SRC___SUPPORT_MACROS_OPTIMIZATION_H
#define LLVM_LIBC_SRC___SUPPORT_MACROS_OPTIMIZATION_H
-#include "src/__support/macros/attributes.h" // LIBC_INLINE
+#include "src/__support/macros/attributes.h" // LIBC_INLINE
#include "src/__support/macros/config.h"
#include "src/__support/macros/properties/compiler.h" // LIBC_COMPILER_IS_CLANG
@@ -24,9 +24,10 @@ LIBC_INLINE constexpr bool expects_bool_condition(T value, T expected) {
}
} // namespace details
} // namespace LIBC_NAMESPACE_DECL
-#define LIBC_LIKELY(x) LIBC_NAMESPACE::details::expects_bool_condition(x, true)
+#define LIBC_LIKELY(x) \
+ LIBC_NAMESPACE::details::expects_bool_condition(!!(x), true)
#define LIBC_UNLIKELY(x) \
- LIBC_NAMESPACE::details::expects_bool_condition(x, false)
+ LIBC_NAMESPACE::details::expects_bool_condition(!!(x), false)
#if defined(LIBC_COMPILER_IS_CLANG)
#define LIBC_LOOP_NOUNROLL _Pragma("nounroll")
diff --git a/libc/src/__support/time/linux/CMakeLists.txt b/libc/src/__support/time/linux/CMakeLists.txt
index 1b41c7cb0a98a9..4297a029866685 100644
--- a/libc/src/__support/time/linux/CMakeLists.txt
+++ b/libc/src/__support/time/linux/CMakeLists.txt
@@ -9,6 +9,7 @@ add_header_library(
libc.src.__support.common
libc.src.__support.error_or
libc.src.__support.OSUtil.osutil
+ libc.src.__support.OSUtil.vdso
)
add_header_library(
diff --git a/libc/src/__support/time/linux/clock_gettime.h b/libc/src/__support/time/linux/clock_gettime.h
index eca1ba70de5924..71f77594352613 100644
--- a/libc/src/__support/time/linux/clock_gettime.h
+++ b/libc/src/__support/time/linux/clock_gettime.h
@@ -11,6 +11,8 @@
#include "hdr/types/clockid_t.h"
#include "hdr/types/struct_timespec.h"
+#include "src/__support/OSUtil/linux/vdso.h"
+#include "src/__support/OSUtil/linux/x86_64/vdso.h"
#include "src/__support/OSUtil/syscall.h"
#include "src/__support/common.h"
#include "src/__support/error_or.h"
@@ -20,11 +22,18 @@
namespace LIBC_NAMESPACE_DECL {
namespace internal {
LIBC_INLINE ErrorOr<int> clock_gettime(clockid_t clockid, timespec *ts) {
+ using namespace vdso;
#if SYS_clock_gettime
+ TypedSymbol<VDSOSym::ClockGetTime> clock_gettime;
+ if (LIBC_LIKELY(clock_gettime))
+ return clock_gettime(clockid, ts);
int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime,
static_cast<long>(clockid),
reinterpret_cast<long>(ts));
#elif defined(SYS_clock_gettime64)
+ TypedSymbol<VDSOSym::ClockGetTime64> clock_gettime64;
+ if (LIBC_LIKELY(clock_gettime64))
+ return clock_gettime64(clockid, ts);
static_assert(
sizeof(time_t) == sizeof(int64_t),
"SYS_clock_gettime64 requires struct timespec with 64-bit members.");
>From 043dae517043eaa029eb21c6a8a2ace543c558d8 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <yifanzhu at rochester.edu>
Date: Fri, 13 Sep 2024 10:48:25 -0400
Subject: [PATCH 2/2] fix
---
libc/src/__support/macros/optimization.h | 7 ++--
libc/src/__support/time/linux/clock_gettime.h | 38 ++++++++++++-------
2 files changed, 28 insertions(+), 17 deletions(-)
diff --git a/libc/src/__support/macros/optimization.h b/libc/src/__support/macros/optimization.h
index af9954151ed88c..5ffd474d35c54d 100644
--- a/libc/src/__support/macros/optimization.h
+++ b/libc/src/__support/macros/optimization.h
@@ -10,7 +10,7 @@
#ifndef LLVM_LIBC_SRC___SUPPORT_MACROS_OPTIMIZATION_H
#define LLVM_LIBC_SRC___SUPPORT_MACROS_OPTIMIZATION_H
-#include "src/__support/macros/attributes.h" // LIBC_INLINE
+#include "src/__support/macros/attributes.h" // LIBC_INLINE
#include "src/__support/macros/config.h"
#include "src/__support/macros/properties/compiler.h" // LIBC_COMPILER_IS_CLANG
@@ -24,10 +24,9 @@ LIBC_INLINE constexpr bool expects_bool_condition(T value, T expected) {
}
} // namespace details
} // namespace LIBC_NAMESPACE_DECL
-#define LIBC_LIKELY(x) \
- LIBC_NAMESPACE::details::expects_bool_condition(!!(x), true)
+#define LIBC_LIKELY(x) LIBC_NAMESPACE::details::expects_bool_condition(x, true)
#define LIBC_UNLIKELY(x) \
- LIBC_NAMESPACE::details::expects_bool_condition(!!(x), false)
+ LIBC_NAMESPACE::details::expects_bool_condition(x, false)
#if defined(LIBC_COMPILER_IS_CLANG)
#define LIBC_LOOP_NOUNROLL _Pragma("nounroll")
diff --git a/libc/src/__support/time/linux/clock_gettime.h b/libc/src/__support/time/linux/clock_gettime.h
index 71f77594352613..517cca91391a74 100644
--- a/libc/src/__support/time/linux/clock_gettime.h
+++ b/libc/src/__support/time/linux/clock_gettime.h
@@ -12,34 +12,46 @@
#include "hdr/types/clockid_t.h"
#include "hdr/types/struct_timespec.h"
#include "src/__support/OSUtil/linux/vdso.h"
-#include "src/__support/OSUtil/linux/x86_64/vdso.h"
#include "src/__support/OSUtil/syscall.h"
#include "src/__support/common.h"
#include "src/__support/error_or.h"
#include "src/__support/macros/config.h"
#include <sys/syscall.h>
+#if defined(SYS_clock_gettime64)
+#include <linux/time_types.h>
+#endif
+
namespace LIBC_NAMESPACE_DECL {
namespace internal {
LIBC_INLINE ErrorOr<int> clock_gettime(clockid_t clockid, timespec *ts) {
using namespace vdso;
-#if SYS_clock_gettime
+ int ret;
+#if defined(SYS_clock_gettime)
TypedSymbol<VDSOSym::ClockGetTime> clock_gettime;
- if (LIBC_LIKELY(clock_gettime))
- return clock_gettime(clockid, ts);
- int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime,
- static_cast<long>(clockid),
- reinterpret_cast<long>(ts));
+ if (LIBC_LIKELY(clock_gettime != nullptr))
+ ret = clock_gettime(clockid, ts);
+ else
+ ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime,
+ static_cast<long>(clockid),
+ reinterpret_cast<long>(ts));
#elif defined(SYS_clock_gettime64)
- TypedSymbol<VDSOSym::ClockGetTime64> clock_gettime64;
- if (LIBC_LIKELY(clock_gettime64))
- return clock_gettime64(clockid, ts);
static_assert(
sizeof(time_t) == sizeof(int64_t),
"SYS_clock_gettime64 requires struct timespec with 64-bit members.");
- int ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime64,
- static_cast<long>(clockid),
- reinterpret_cast<long>(ts));
+
+ TypedSymbol<VDSOSym::ClockGetTime64> clock_gettime64;
+ __kernel_timespec ts64{};
+ if (LIBC_LIKELY(clock_gettime64 != nullptr))
+ ret = clock_gettime64(clockid, &ts64);
+ else
+ ret = LIBC_NAMESPACE::syscall_impl<int>(SYS_clock_gettime64,
+ static_cast<long>(clockid),
+ reinterpret_cast<long>(&ts64));
+ if (ret == 0) {
+ ts->tv_sec = static_cast<decltype(ts->tv_sec)>(ts64.tv_sec);
+ ts->tv_nsec = static_cast<decltype(ts->tv_nsec)>(ts64.tv_nsec);
+ }
#else
#error "SYS_clock_gettime and SYS_clock_gettime64 syscalls not available."
#endif
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