tools/nolibc: add support for sys_llseek()

Not all architectures have the old sys_lseek(), notably riscv32.
Implement lseek() in terms of sys_llseek() in that case.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://lore.kernel.org/r/20250209-nolibc-dir-v2-1-57cc1da8558b@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

Author: t-8ch

tools/include/nolibc/sys.h

@@ -597,10 +597,37 @@ off_t sys_lseek(int fd, off_t offset, int whence)
 #endif
 }
 
+static __attribute__((unused))
+int sys_llseek(int fd, unsigned long offset_high, unsigned long offset_low,
+	       __kernel_loff_t *result, int whence)
+{
+#ifdef __NR_llseek
+	return my_syscall5(__NR_llseek, fd, offset_high, offset_low, result, whence);
+#else
+	return __nolibc_enosys(__func__, fd, offset_high, offset_low, result, whence);
+#endif
+}
+
 static __attribute__((unused))
 off_t lseek(int fd, off_t offset, int whence)
 {
-	return __sysret(sys_lseek(fd, offset, whence));
+	__kernel_loff_t loff = 0;
+	off_t result;
+	int ret;
+
+	result = sys_lseek(fd, offset, whence);
+	if (result == -ENOSYS) {
+		/* Only exists on 32bit where nolibc off_t is also 32bit */
+		ret = sys_llseek(fd, 0, offset, &loff, whence);
+		if (ret < 0)
+			result = ret;
+		else if (loff != (off_t)loff)
+			result = -EOVERFLOW;
+		else
+			result = loff;
+	}
+
+	return __sysret(result);
 }