Add /dev/zero.

sortix/Makefile

@@ -96,6 +96,7 @@ fs/kram.o \
 fs/null.o \
 fs/user.o \
 fs/util.o \
+fs/zero.o \
 identity.o \
 initrd.o \
 inode.o \

sortix/fs/zero.cpp

@@ -0,0 +1,102 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of Sortix.
+
+    Sortix 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.
+
+    Sortix 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
+    Sortix. If not, see <http://www.gnu.org/licenses/>.
+
+    fs/zero.cpp
+    Bit bucket special device.
+
+*******************************************************************************/
+
+#include <sys/types.h>
+
+#include <stdint.h>
+#include <string.h>
+
+#include <sortix/stat.h>
+
+#include <sortix/kernel/inode.h>
+#include <sortix/kernel/ioctx.h>
+
+#include "zero.h"
+
+namespace Sortix {
+
+Zero::Zero(dev_t dev, ino_t ino, uid_t owner, gid_t group, mode_t mode)
+{
+	inode_type = INODE_TYPE_STREAM;
+	if ( !dev )
+		dev = (dev_t) this;
+	if ( !ino )
+		ino = (ino_t) this;
+	this->type = S_IFCHR;
+	this->stat_uid = owner;
+	this->stat_gid = group;
+	this->stat_mode = (mode & S_SETABLE) | this->type;
+	this->stat_size = 0;
+	this->stat_blksize = 1;
+	this->dev = dev;
+	this->ino = ino;
+}
+
+Zero::~Zero()
+{
+}
+
+int Zero::truncate(ioctx_t* /*ctx*/, off_t /*length*/)
+{
+	return 0;
+}
+
+off_t Zero::lseek(ioctx_t* /*ctx*/, off_t offset, int /*whence*/)
+{
+	return offset;
+}
+
+ssize_t Zero::read(ioctx_t* ctx, uint8_t* buf, size_t count)
+{
+	const size_t ZERO_MEM_SIZE = 128;
+	uint8_t zero_mem[ZERO_MEM_SIZE];
+	memset(zero_mem, 0, ZERO_MEM_SIZE);
+	size_t sofar = 0;
+	while ( sofar < count )
+	{
+		size_t left = count - sofar;
+		size_t amount = left < ZERO_MEM_SIZE ? left : ZERO_MEM_SIZE;
+		ctx->copy_to_dest(buf + sofar, zero_mem, amount);
+		sofar += amount;
+	}
+	return (ssize_t) sofar;
+}
+
+ssize_t Zero::pread(ioctx_t* ctx, uint8_t* buf, size_t count, off_t /*off*/)
+{
+	return read(ctx, buf, count);
+}
+
+ssize_t Zero::write(ioctx_t* /*ctx*/, const uint8_t* /*buf*/, size_t count)
+{
+	return count;
+}
+
+ssize_t Zero::pwrite(ioctx_t* /*ctx*/, const uint8_t* /*buf*/, size_t count,
+                    off_t /*off*/)
+{
+	return count;
+}
+
+} // namespace Sortix

sortix/fs/zero.h

@@ -0,0 +1,48 @@
+/*******************************************************************************
+
+    Copyright(C) Jonas 'Sortie' Termansen 2013.
+
+    This file is part of Sortix.
+
+    Sortix 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.
+
+    Sortix 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
+    Sortix. If not, see <http://www.gnu.org/licenses/>.
+
+    fs/zero.h
+    Bit bucket special device.
+
+*******************************************************************************/
+
+#ifndef SORTIX_FS_ZERO_H
+#define SORTIX_FS_ZERO_H
+
+#include <sortix/kernel/inode.h>
+
+namespace Sortix {
+
+class Zero : public AbstractInode
+{
+public:
+	Zero(dev_t dev, ino_t ino, uid_t owner, gid_t group, mode_t mode);
+	virtual ~Zero();
+	virtual int truncate(ioctx_t* ctx, off_t length);
+	virtual off_t lseek(ioctx_t* ctx, off_t offset, int whence);
+	virtual ssize_t read(ioctx_t* ctx, uint8_t* buf, size_t count);
+	virtual ssize_t pread(ioctx_t* ctx, uint8_t* buf, size_t count, off_t off);
+	virtual ssize_t write(ioctx_t* ctx, const uint8_t* buf, size_t count);
+	virtual ssize_t pwrite(ioctx_t* ctx, const uint8_t* buf, size_t count,
+	                       off_t off);
+};
+
+} // namespace Sortix
+
+#endif

sortix/kernel.cpp

@@ -75,6 +75,7 @@
 #include "fs/kram.h"
 #include "fs/null.h"
 #include "fs/user.h"
+#include "fs/zero.h"
 #include "identity.h"
 #include "initrd.h"
 #include "io.h"
@@ -538,6 +539,14 @@ static void BootThread(void* /*user*/)
 	if ( LinkInodeInDir(&ctx, slashdev, "null", null_device) != 0 )
 		Panic("Unable to link /dev/null to the null device.");
 
+	// Register the zero device as /dev/zero.
+	Ref<Inode> zero_device(new Zero(slashdev->dev, (ino_t) 0, (uid_t) 0,
+	                                (gid_t) 0, (mode_t) 0666));
+	if ( !zero_device )
+		Panic("Could not allocate a zero device");
+	if ( LinkInodeInDir(&ctx, slashdev, "zero", zero_device) != 0 )
+		Panic("Unable to link /dev/zero to the zero device.");
+
 	// Initialize the COM ports.
 	COM::Init("/dev", slashdev);