mescc: Mes C Library: Support GNU Tar: Add readlink, symlink.

* lib/linux/gnu.c (readlink, symlink): New function.
* include/unistd.h (readlink, symlink): Declare.
* include/linux/x86/syscall.h (SYS_readlink, SYS_symlink): New macro.
* include/linux/x86_64/syscall.h (SYS_symlink, SYS_readlink): New
macro.

build-aux/configure-lib.sh

@@ -308,12 +308,14 @@ lib/linux/lstat.c
 lib/linux/mkdir.c
 lib/linux/nanosleep.c
 lib/linux/pipe.c
+lib/linux/readlink.c
 lib/linux/rename.c
 lib/linux/setgid.c
 lib/linux/settimer.c
 lib/linux/setuid.c
 lib/linux/signal.c
 lib/linux/sigprogmask.c
+lib/linux/symlink.c
 "
 fi
 

include/linux/x86/syscall.h

@@ -83,4 +83,8 @@
 // make+POSIX
 #define SYS_sigprocmask 0x7e
 
+// tar
+#define SYS_symlink   0x53
+#define SYS_readlink  0x55
+
 #endif // __MES_LINUX_X86_SYSCALL_H

include/linux/x86_64/syscall.h

@@ -80,4 +80,8 @@
 // make+SYSTEM_LIBC
 #define SYS_rt_sigprocmask 0x0e
 
+// tar
+#define SYS_symlink   0x58
+#define SYS_readlink  0x59
+
 #endif // __MES_LINUX_X86_64_SYSCALL_H

include/unistd.h

@@ -77,15 +77,17 @@ gid_t getegid (void);
 pid_t getpid (void);
 pid_t getppid (void);
 int isatty (int fd);
-int link (char const *oldname, char const *newname);
+int link (char const *old_name, char const *new_name);
 off_t lseek (int fd, off_t offset, int whence);
 ssize_t read (int fd, void *buffer, size_t size);
+ssize_t readlink (char const *file_name, char *buffer, size_t size);
 #if __SBRK_CHAR_PTRDIFF
 /* xmalloc in binutils <= 2.10.1 uses this old prototype */
 char *sbrk (ptrdiff_t delta);
 #else
 void *sbrk (intptr_t delta);
 #endif
+int symlink (char const *old_name, char const *new_name);
 int unlink (char const *file_name);
 ssize_t write (int filedes, void const *buffer, size_t size);
 pid_t getpid (void);

lib/linux/readlink.c

@@ -0,0 +1,29 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes 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 General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/syscall.h>
+#include <syscall.h>
+#include <sys/stat.h>
+
+ssize_t
+readlink (char const *file_name, char *buffer, size_t size)
+{
+  return _sys_call3 (SYS_readlink, (long) file_name, (long) buffer, (long) size);
+}

lib/linux/symlink.c

@@ -0,0 +1,29 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2018,2019 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes 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 General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/syscall.h>
+#include <syscall.h>
+#include <unistd.h>
+
+int
+symlink (char const *old_name, char const *new_name)
+{
+  return _sys_call2 (SYS_symlink, (long) old_name, (long) new_name);
+}