linux-kernel - [PATCH 1/6] perf bench futex: Add support for 32-bit systems with 64-bit time

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Date:   Fri, 28 Oct 2022 19:56:27 +1000
From:   Alistair Francis <alistair.francis@...nsource.wdc.com>
To:     linux-kernel@...r.kernel.org
Cc:     acme@...nel.org, dave@...olabs.net,
        alexander.shishkin@...ux.intel.com, tglx@...utronix.de,
        namhyung@...nel.org, jolsa@...hat.com,
        linux-perf-users@...r.kernel.org, acme@...hat.com,
        dvhart@...radead.org, mark.rutland@....com, peterz@...radead.org,
        arnd@...db.de, alistair23@...il.com,
        linux-riscv@...ts.infradead.org, mingo@...hat.com,
        alistair.francis@....com, atish.patra@....com
Subject: [PATCH 1/6] 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).

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@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Alistair Francis <alistair23@...il.com>
Cc: Atish Patra <atish.patra@....com>
Cc: Darren Hart <dvhart@...radead.org>
Cc: Davidlohr Bueso <dave@...olabs.net>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-riscv@...ts.infradead.org
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Reviewed-by: Arnd Bergmann <arnd@...db.de>
Message-Id: <20211209235857.423773-1-alistair.francis@...nsource.wdc.com>
---
 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
 }
 
 /**
-- 
2.37.3