Add readlink{,at}(2).

libc/Makefile

@@ -212,6 +212,8 @@ putc.o \
 raise.o \
 rand.o \
 readdirents.o \
+readlinkat.o \
+readlink.o \
 read.o \
 realpath.o \
 removeat.o \

libc/include/unistd.h

@@ -111,8 +111,6 @@ int lockf(int, int, off_t);
 int nice(int);
 long pathconf(const char*, int);
 int pause(void);
-ssize_t readlink(const char* restrict, char* restrict, size_t);
-ssize_t readlinkat(int, const char* restrict, char* restrict, size_t);
 int setegid(gid_t);
 int seteuid(uid_t);
 int setgid(gid_t);
@@ -170,6 +168,8 @@ off_t lseek(int, off_t, int);
 int pipe(int [2]);
 ssize_t pread(int, void*, size_t, off_t);
 ssize_t pwrite(int, const void*, size_t, off_t);
+ssize_t readlink(const char* restrict, char* restrict, size_t);
+ssize_t readlinkat(int, const char* restrict, char* restrict, size_t);
 ssize_t read(int, void*, size_t);
 int rmdir(const char*);
 unsigned sleep(unsigned);

libc/readlink.cpp

@@ -0,0 +1,32 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of the Sortix C Library.
+
+    The Sortix C Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    The Sortix C Library 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 Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
+
+    readlink.cpp
+    Read contents of symbolic link.
+
+*******************************************************************************/
+
+#include <fcntl.h>
+#include <unistd.h>
+
+extern "C" ssize_t readlink(const char* restrict path, char* restrict buf,
+                            size_t size)
+{
+	return readlinkat(AT_FDCWD, path, buf, size);
+}

libc/readlinkat.cpp

@@ -0,0 +1,37 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of the Sortix C Library.
+
+    The Sortix C Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or (at your
+    option) any later version.
+
+    The Sortix C Library 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 Lesser General Public
+    License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
+
+    readlinkat.cpp
+    Read contents of symbolic link.
+
+*******************************************************************************/
+
+#include <sys/syscall.h>
+
+#include <fcntl.h>
+#include <unistd.h>
+
+DEFN_SYSCALL4(ssize_t, sys_readlinkat, SYSCALL_READLINKAT, int,
+              const char* restrict, char* restrict, size_t);
+
+extern "C" ssize_t readlinkat(int dirfd, const char* restrict path,
+                              char* restrict buf, size_t size)
+{
+	return sys_readlinkat(dirfd, path, buf, size);
+}

sortix/descriptor.cpp

@@ -420,6 +420,8 @@ int Descriptor::rename_here(ioctx_t* ctx, Ref<Descriptor> from,
 
 ssize_t Descriptor::readlink(ioctx_t* ctx, char* buf, size_t bufsize)
 {
+	if ( (size_t) SSIZE_MAX < bufsize )
+		bufsize = (size_t) SSIZE_MAX;
 	return vnode->readlink(ctx, buf, bufsize);
 }
 

sortix/include/sortix/syscallnum.h

@@ -95,6 +95,7 @@
 #define SYSCALL_FSM_FSBIND 71
 #define SYSCALL_PPOLL 72
 #define SYSCALL_RENAMEAT 73
-#define SYSCALL_MAX_NUM 74 /* index of highest constant + 1 */
+#define SYSCALL_READLINKAT 74
+#define SYSCALL_MAX_NUM 75 /* index of highest constant + 1 */
 
 #endif

sortix/io.cpp

@@ -540,6 +540,25 @@ static int sys_renameat(int olddirfd, const char* oldpath,
 	return ret;
 }
 
+// TODO: This should probably be moved into user-space. It'd be nice if
+// user-space could just open the symlink and read/write it like a regular file.
+static ssize_t sys_readlinkat(int dirfd, const char* path, char* buf, size_t size)
+{
+	char* pathcopy = GetStringFromUser(path);
+	if ( !pathcopy )
+		return -1;
+	ioctx_t ctx; SetupUserIOCtx(&ctx);
+	const char* relpath = pathcopy;
+	Ref<Descriptor> from = PrepareLookup(&relpath, dirfd);
+	if ( !from ) { delete[] pathcopy; return -1; }
+	// TODO: Open the symbolic link, instead of what it points to!
+	Ref<Descriptor> desc = from->open(&ctx, relpath, O_RDONLY);
+	delete[] pathcopy;
+	if ( !desc )
+		return -1;
+	return (int) desc->readlink(&ctx, buf, size);
+}
+
 void Init()
 {
 	Syscall::Register(SYSCALL_ACCESS, (void*) sys_access);
@@ -570,6 +589,7 @@ void Init()
 	Syscall::Register(SYSCALL_PREAD, (void*) sys_pread);
 	Syscall::Register(SYSCALL_PWRITE, (void*) sys_pwrite);
 	Syscall::Register(SYSCALL_READDIRENTS, (void*) sys_readdirents);
+	Syscall::Register(SYSCALL_READLINKAT, (void*) sys_readlinkat);
 	Syscall::Register(SYSCALL_READ, (void*) sys_read);
 	Syscall::Register(SYSCALL_RENAMEAT, (void*) sys_renameat);
 	Syscall::Register(SYSCALL_RMDIR, (void*) sys_rmdir);