[PATCH v3 1/3] date: Use 64 prefix syscall if we have to

[Alistair Francis]

Some 32-bit architectures no longer have the 32-bit time_t syscalls.
Instead they have suffixed syscalls that returns a 64-bit time_t. If
the architecture doesn't have the non-suffixed syscall and is using a
64-bit time_t let's use the suffixed syscall instead.

This fixes build issues when building for RISC-V 32-bit with 5.1+ kernel
headers.

If an architecture only supports the suffixed syscalls, but is still
using a 32-bit time_t fall back to the libc call.

Signed-off-by: Alistair Francis <alistair.francis at wdc.com>
---
v2:
 - Fix comment typo

 coreutils/date.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/coreutils/date.c b/coreutils/date.c
index feb400430..731241536 100644
--- a/coreutils/date.c
+++ b/coreutils/date.c
@@ -36,7 +36,7 @@
 //config:# defaults to "no": stat's nanosecond field is a bit non-portable
 //config:config FEATURE_DATE_NANO
 //config:	bool "Support %[num]N nanosecond format specifier"
-//config:	default n  # syscall(__NR_clock_gettime)
+//config:	default n  # syscall(__NR_clock_gettime) or syscall(__NR_clock_gettime64)
 //config:	depends on DATE
 //config:	select PLATFORM_LINUX
 //config:	help
@@ -271,10 +271,17 @@ int date_main(int argc UNUSED_PARAM, char **argv)
 		 */
 #endif
 	} else {
-#if ENABLE_FEATURE_DATE_NANO
+#if ENABLE_FEATURE_DATE_NANO && defined(__NR_clock_gettime)
 		/* libc has incredibly messy way of doing this,
 		 * typically requiring -lrt. We just skip all this mess */
 		syscall(__NR_clock_gettime, CLOCK_REALTIME, &ts);
+#elif ENABLE_FEATURE_DATE_NANO && __TIMESIZE == 64
+		/* Let's only support the 64 suffix syscalls for 64-bit time_t.
+		 * This simplifies the code for us as we don't need to convert
+		 * between 64-bit and 32-bit. We also don't have a way to
+		 * report overflow errors here.
+		 */
+		syscall(__NR_clock_gettime64, CLOCK_REALTIME, &ts);
 #else
 		time(&ts.tv_sec);
 #endif
-- 
2.23.0