linux-kernel - [PATCH v2 2/2] perf bench: Add support for 32-bit systems with 64-bit time

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Date:   Fri, 10 Sep 2021 14:31:02 +1000
From:   Alistair Francis <alistair.francis@...nsource.wdc.com>
To:     linux-riscv@...ts.infradead.org, linux-perf-users@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, alistair23@...il.com,
        namhyung@...nel.org, jolsa@...hat.com,
        alexander.shishkin@...ux.intel.com, mark.rutland@....com,
        acme@...nel.org, dave@...olabs.net, dvhart@...radead.org,
        peterz@...radead.org, mingo@...hat.com, tglx@...utronix.de,
        atish.patra@....com, arnd@...db.de,
        Alistair Francis <alistair.francis@....com>
Subject: [PATCH v2 2/2] perf bench: Add support for 32-bit systems with 64-bit time_t

From: Alistair Francis <alistair.francis@....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.

Signed-off-by: Alistair Francis <alistair.francis@....com>
---
 tools/perf/bench/futex.h | 43 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
index f80a4759ee79b..09c5596726c60 100644
--- a/tools/perf/bench/futex.h
+++ b/tools/perf/bench/futex.h
@@ -27,6 +27,12 @@ struct bench_futex_parameters {
 	unsigned int nrequeue;
 };
 
+/* A version of 'struct timespec' with 32-bit time_t and nanoseconds.  */
+struct __timespec32 {
+	__kernel_long_t tv_sec;
+	__kernel_long_t tv_nsec;
+};
+
 /**
  * futex_syscall() - SYS_futex syscall wrapper
  * @uaddr:	address of first futex
@@ -49,14 +55,49 @@ static inline int
 futex_syscall(u_int32_t *uaddr, int op, u_int32_t val, struct timespec *timeout,
 	u_int32_t *uaddr2, int val3, int opflags)
 {
-	return syscall(SYS_futex, uaddr, op | opflags, val, ts32, uaddr2, val3);
+#if defined(SYS_futex_time64)
+	if (sizeof(*timeout) != sizeof(struct __timespec32)) {
+		int ret =  syscall(SYS_futex_time64, uaddr, op | opflags, val, timeout,
+				   uaddr2, val3);
+	if (ret == 0 || errno != ENOSYS)
+		return ret;
+	}
+#endif
+
+#if defined(SYS_futex)
+	if (sizeof(*timeout) == sizeof(struct __timespec32))
+		return syscall(SYS_futex, uaddr, op | opflags, val, timeout, uaddr2, val3);
+
+	if (timeout && timeout->tv_sec == (long)timeout->tv_sec) {
+		struct __timespec32 ts32;
+
+		ts32.tv_sec = (__kernel_long_t) timeout->tv_sec;
+		ts32.tv_nsec = (__kernel_long_t) timeout->tv_nsec;
+
+		return syscall(SYS_futex, uaddr, op | opflags, val, ts32, uaddr2, val3);
+	} else if (!timeout) {
+		return syscall(SYS_futex, uaddr, op | opflags, val, NULL, uaddr2, val3);
+	}
+#endif
+
+	errno = ENOSYS;
+	return -1;
 }
 
 static inline int
 futex_syscall_nr_requeue(u_int32_t *uaddr, int op, u_int32_t val, int nr_requeue,
 	u_int32_t *uaddr2, int val3, int opflags)
 {
+#if defined(SYS_futex_time64)
+	int ret =  syscall(SYS_futex_time64, uaddr, op | opflags, val, nr_requeue,
+			   uaddr2, val3);
+	if (ret == 0 || errno != ENOSYS)
+		return ret;
+#endif
+
+#if defined(SYS_futex)
 	return syscall(SYS_futex, uaddr, op | opflags, val, nr_requeue, uaddr2, val3);
+#endif
 }
 
 /**
-- 
2.31.1