linux-kernel - [PATCH v5 2/4] perf bench futex: Add support for 32-bit systems with 64-bit time

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Message-Id: <20211022013343.2262938-2-alistair.francis@opensource.wdc.com>
Date:   Fri, 22 Oct 2021 11:33:41 +1000
From:   Alistair Francis <alistair.francis@...nsource.wdc.com>
To:     linux-perf-users@...r.kernel.org, linux-riscv@...ts.infradead.org
Cc:     dvhart@...radead.org, tglx@...utronix.de,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, mingo@...hat.com, atish.patra@....com,
        linux-kernel@...r.kernel.org, arnd@...db.de, alistair23@...il.com,
        mark.rutland@....com, acme@...nel.org, peterz@...radead.org,
        dave@...olabs.net, Alistair Francis <alistair.francis@....com>,
        Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH v5 2/4] perf bench futex: 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.

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

Signed-off-by: Alistair Francis <alistair.francis@....com>
Reviewed-by: Arnd Bergmann <arnd@...db.de>
Acked-by: Davidlohr Bueso <dbueso@...e.de>
---
 tools/perf/bench/futex.h | 43 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/tools/perf/bench/futex.h b/tools/perf/bench/futex.h
index ebdc2b032afc1..6a7dd86871eb8 100644
--- a/tools/perf/bench/futex.h
+++ b/tools/perf/bench/futex.h
@@ -8,10 +8,12 @@
 #ifndef _FUTEX_H
 #define _FUTEX_H
 
+#include <errno.h>
 #include <unistd.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
 #include <linux/futex.h>
+#include <linux/time_types.h>
 
 struct bench_futex_parameters {
 	bool silent;
@@ -28,7 +30,7 @@ struct bench_futex_parameters {
 };
 
 /**
- * futex_syscall() - SYS_futex syscall wrapper
+ * 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 +51,49 @@ 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