[PATCH v3 1/6] perf bench futex: Add support for 32-bit systems with 64-bit time_t

* [PATCH v3 1/6] perf bench futex: Add support for 32-bit systems with 64-bit time_t
@ 2021-11-26  6:00 Alistair Francis
  2021-11-26  6:00 ` [PATCH v3 2/6] selftests: futex: Call the futex syscall from a function Alistair Francis
                   ` (6 more replies)
  0 siblings, 7 replies; 13+ messages in thread
From: Alistair Francis @ 2021-11-26  6:00 UTC (permalink / raw)
  To: linux-kernel
  Cc: tglx, arnd, namhyung, peterz, alistair23, jolsa, dave, mingo,
	dvhart, acme, linux-perf-users, mark.rutland, alexander.shishkin,
	Alistair Francis, Atish Patra, linux-riscv,
	Arnaldo Carvalho de Melo

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>
---
 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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