linux-kernel - [PATCH v2 07/13] tools/nolibc/select: avoid libgcc 64-bit multiplications

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Message-Id: <20251122-nolibc-uapi-types-v2-7-b814a43654f5@weissschuh.net>
Date: Sat, 22 Nov 2025 17:59:13 +0100
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>, Shuah Khan <shuah@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org, 
 linux-kselftest@...r.kernel.org, 
 Thomas Weißschuh <linux@...ssschuh.net>
Subject: [PATCH v2 07/13] tools/nolibc/select: avoid libgcc 64-bit
 multiplications

timeval::tv_usec is going to be 64-bit wide even on 32-bit
architectures. As not all architectures support 64-bit multiplications
instructions, calls to libgcc (__multi3()) may be emitted by the
compiler which are not provided by nolibc.

As tv_usec and tv_nsec are guaranteed to always fit into an uint32_t,
perform a 32-bit multiplication instead.

Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
---
 tools/include/nolibc/sys/select.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/include/nolibc/sys/select.h b/tools/include/nolibc/sys/select.h
index f8870ad49687..80cb3755ba18 100644
--- a/tools/include/nolibc/sys/select.h
+++ b/tools/include/nolibc/sys/select.h
@@ -68,7 +68,7 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
 
 	if (timeout) {
 		t.tv_sec  = timeout->tv_sec;
-		t.tv_nsec = timeout->tv_usec * 1000;
+		t.tv_nsec = (uint32_t)timeout->tv_usec * 1000;
 	}
 	return my_syscall6(__NR_pselect6_time64, nfds, rfds, wfds, efds, timeout ? &t : NULL, NULL);
 #else
@@ -76,7 +76,7 @@ int sys_select(int nfds, fd_set *rfds, fd_set *wfds, fd_set *efds, struct timeva
 
 	if (timeout) {
 		t.tv_sec  = timeout->tv_sec;
-		t.tv_nsec = timeout->tv_usec * 1000;
+		t.tv_nsec = (uint32_t)timeout->tv_usec * 1000;
 	}
 	return my_syscall6(__NR_pselect6, nfds, rfds, wfds, efds, timeout ? &t : NULL, NULL);
 #endif

-- 
2.52.0