posix: POSIX_sysconf

sys/include/posix.h

@@ -242,6 +242,24 @@ typedef enum PosixFDCmds
 	PosixFDCSetFL
 } PosixFDCmds;
 
+/* https://pubs.opengroup.org/onlinepubs/9699919799/functions/sysconf.html
+ */
+typedef enum PosixSysConfNames
+{
+	/* Posix 1 */
+	PosixSCNArgMax = 1,	// _SC_ARG_MAX
+	PosixSCNChildMax,	// _SC_CHILD_MAX
+	PosixSCNHostNameMax,	// _SC_HOST_NAME_MAX
+	PosixSCNLoginNameMax,	// _SC_LOGIN_NAME_MAX
+	PosixSCNClockTicks,	// _SC_CLK_TCK
+	PosixSCNOpenMax,	// _SC_OPEN_MAX
+	PosixSCNPageSize,	// _SC_PAGESIZE
+	PosixSCNPosixVersion,	// _SC_VERSION
+
+	/* Posix 2 */
+	PosixSCNLineMax		// _SC_LINE_MAX
+} PosixSysConfNames;
+
 #endif /* _LIBPOSIX_DEF */
 
 #ifndef _LIBPOSIX_H
@@ -305,6 +323,7 @@ extern unsigned int POSIX_sleep(unsigned int seconds);
 extern int POSIX_pipe(int *errnop, int fildes[2]);
 extern int POSIX_umask(int *errnop, int mask);
 extern int POSIX_fcntl(int *errnop, int fd, PosixFDCmds cmd, uintptr_t arg);
+extern long POSIX_sysconf(int *errnop, PosixSysConfNames name);
 
 extern int POSIX_sigaddset(int *errnop, PosixSignalMask *set, int signo);
 extern int POSIX_sigdelset(int *errnop, PosixSignalMask *set, int signo);

sys/src/lib/posix/build.json

@@ -1,6 +1,7 @@
 {
 	"LibPosix": {
 		"Cflags": [
+			"-DPORTABLE_SYSCALLS",
 			"-DARCH=\"$ARCH\"",
 			"-fasm",
 			"-I."
@@ -27,6 +28,7 @@
 			"sigqueue.c",
 			"sigsets.c",
 			"sigsuspend.c",
+			"sysconf.c",
 			"termios.c",
 			"timers.c"
 		]

sys/src/lib/posix/sysconf.c

@@ -0,0 +1,57 @@
+/*
+ * This file is part of Jehanne.
+ *
+ * Copyright (C) 2019 Giacomo Tesio <giacomo@tesio.it>
+ *
+ * This is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, version 3 of the License.
+ *
+ * Jehanne is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Jehanne.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <u.h>
+#include <lib9.h>
+#include <posix.h>
+#include "internal.h"
+
+long
+POSIX_sysconf(int *errnop, PosixSysConfNames name)
+{
+	/* "arbitrary" means that no actual limit exists */
+
+	switch(name){
+	case PosixSCNArgMax:		// _SC_ARG_MAX
+		/* arbitrary */
+		return 4096;
+	case PosixSCNChildMax:		// _SC_CHILD_MAX
+		/* arbitrary */
+		return 128;
+	case PosixSCNHostNameMax:	// _SC_HOST_NAME_MAX
+	case PosixSCNLoginNameMax:	// _SC_LOGIN_NAME_MAX
+		/* See Proc.genbuf in /sys/src/kern/port/portdat.h */
+		return 128;
+	case PosixSCNClockTicks:	// _SC_CLK_TCK
+		/* See HZ in /sys/src/kern/amd64/dat.h */
+		return 100;
+	case PosixSCNOpenMax:		// _SC_OPEN_MAX
+		/* arbitrary */
+		return 256;
+	case PosixSCNPageSize:		// _SC_PAGESIZE
+		return 4096;
+	case PosixSCNPosixVersion:	// _SC_VERSION
+		return 200101;
+	case PosixSCNLineMax:		// _SC_LINE_MAX
+		/* arbitrary */
+		return 4096;
+
+	default:
+		*errnop = __libposix_get_errno(PosixENOSYS);
+		return -1;
+	}
+}