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Subject[PATCH v4 1/6] perf bench futex: Add support for 32-bit systems with 64-bit time_t
Date
From: Alistair Francis <alistair.francis@wdc.com>

Some 32-bit architectures (such are 32-bit RISC-V) only have a 64-bit
time_t and as such don't have the SYS_futex syscall. This patch will
allow us to use the SYS_futex_time64 syscall on those platforms.

This also converts the futex calls to be y2038 safe (when built for a
5.1+ kernel).

This is a revert of commit ba4026b09d83acf56c040b6933eac7916c27e728
"Revert "perf bench futex: Add support for 32-bit systems with 64-bit time_t"".

The original commit was reverted as including linux/time_types.h would
fail to compile on older kernels. This commit doesn't include
linux/time_types.h to avoid this issue.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alistair Francis <alistair23@gmail.com>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-riscv@lists.infradead.org
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
---
tools/perf/bench/futex.h | 52 +++++++++++++++++++++++++++++++++++++---
1 file changed, 49 insertions(+), 3 deletions(-)

diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
index ebdc2b032afc..385d2bdfaa9f 100644
--- a/tools/perf/bench/futex.h
+++ b/tools/perf/bench/futex.h
@@ -8,6 +8,7 @@
#ifndef _FUTEX_H
#define _FUTEX_H

+#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/types.h>
@@ -28,7 +29,17 @@ struct bench_futex_parameters {
};

/**
- * futex_syscall() - SYS_futex syscall wrapper
+ * This is copied from linux/time_types.h.
+ * We copy this here to avoid compilation failures when running
+ * on systems that don't ship with linux/time_types.h.
+ */
+struct __kernel_old_timespec {
+ __kernel_old_time_t tv_sec; /* seconds */
+ long tv_nsec; /* nanoseconds */
+};
+
+/**
+ * futex_syscall() - __NR_futex syscall wrapper
* @uaddr: address of first futex
* @op: futex op code
* @val: typically expected value of uaddr, but varies by op
@@ -49,14 +60,49 @@ static inline int
futex_syscall(volatile u_int32_t *uaddr, int op, u_int32_t val, struct timespec *timeout,
volatile u_int32_t *uaddr2, int val3, int opflags)
{
- return syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3);
+#if defined(__NR_futex_time64)
+ if (sizeof(*timeout) != sizeof(struct __kernel_old_timespec)) {
+ int ret = syscall(__NR_futex_time64, uaddr, op | opflags, val, timeout,
+ uaddr2, val3);
+ if (ret == 0 || errno != ENOSYS)
+ return ret;
+ }
+#endif
+
+#if defined(__NR_futex)
+ if (sizeof(*timeout) == sizeof(struct __kernel_old_timespec))
+ return syscall(__NR_futex, uaddr, op | opflags, val, timeout, uaddr2, val3);
+
+ if (timeout && timeout->tv_sec == (long)timeout->tv_sec) {
+ struct __kernel_old_timespec ts32;
+
+ ts32.tv_sec = (__kernel_long_t) timeout->tv_sec;
+ ts32.tv_nsec = (__kernel_long_t) timeout->tv_nsec;
+
+ return syscall(__NR_futex, uaddr, op | opflags, val, ts32, uaddr2, val3);
+ } else if (!timeout) {
+ return syscall(__NR_futex, uaddr, op | opflags, val, NULL, uaddr2, val3);
+ }
+#endif
+
+ errno = ENOSYS;
+ return -1;
}

static inline int
futex_syscall_nr_requeue(volatile u_int32_t *uaddr, int op, u_int32_t val, int nr_requeue,
volatile u_int32_t *uaddr2, int val3, int opflags)
{
- return syscall(SYS_futex, uaddr, op | opflags, val, nr_requeue, uaddr2, val3);
+#if defined(__NR_futex_time64)
+ int ret = syscall(__NR_futex_time64, uaddr, op | opflags, val, nr_requeue,
+ uaddr2, val3);
+ if (ret == 0 || errno != ENOSYS)
+ return ret;
+#endif
+
+#if defined(__NR_futex)
+ return syscall(__NR_futex, uaddr, op | opflags, val, nr_requeue, uaddr2, val3);
+#endif
}

/**
--
2.31.1
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