Added chroot and append-only options to hostfs.

3 files changed, 76 insertions, 17 deletions

diff --git a/arch/um/fs/hostfs/hostfs.h b/arch/um/fs/hostfs/hostfs.h
index e5af1d5..7cf3b5b 100644
--- a/arch/um/fs/hostfs/hostfs.h
+++ b/arch/um/fs/hostfs/hostfs.h
@@ -38,7 +38,7 @@ extern int stat_file(const char *path, int *dev_out,
 		     unsigned long *mtime_out, unsigned long *ctime_out, 
 		     int *blksize_out, unsigned long long *blocks_out);
 extern int access_file(char *path, int r, int w, int x);
-extern int open_file(char *path, int r, int w);
+extern int open_file(char *path, int r, int w, int append);
 extern int file_type(const char *path, int *rdev);
 extern void *open_dir(char *path, int *err_out);
 extern char *read_dir(void *stream, unsigned long long *pos, 
diff --git a/arch/um/fs/hostfs/hostfs_kern.c b/arch/um/fs/hostfs/hostfs_kern.c
index a4615cf..3a50894 100644
--- a/arch/um/fs/hostfs/hostfs_kern.c
+++ b/arch/um/fs/hostfs/hostfs_kern.c
@@ -17,6 +17,7 @@
 #include "kern.h"
 #include "user_util.h"
 #include "2_5compat.h"
+#include "init.h"
 
 #define file_hostfs_i(file) (&(file)->f_dentry->d_inode->u.hostfs_i)
 
@@ -29,8 +30,9 @@ struct dentry_operations hostfs_dentry_ops = {
 	.d_delete		= hostfs_d_delete,
 };
 
-/* Not changed */
+/* Changed in hostfs_args before the kernel starts running */
 static char *root_ino = "/";
+static int append = 0;
 
 #define HOSTFS_SUPER_MAGIC 0x00c0ffee
 
@@ -38,6 +40,43 @@ static struct inode_operations hostfs_iops;
 static struct inode_operations hostfs_dir_iops;
 static struct address_space_operations hostfs_link_aops;
 
+static int __init hostfs_args(char *options, int *add)
+{
+	char *ptr;
+
+	ptr = strchr(options, ',');
+	if(ptr != NULL)
+		*ptr++ = '\0';
+	if(*options != '\0')
+		root_ino = options;
+
+	options = ptr;
+	while(options){
+		ptr = strchr(options, ',');
+		if(ptr != NULL)
+			*ptr++ = '\0';
+		if(*options != '\0'){
+			if(!strcmp(options, "append"))
+				append = 1;
+			else printf("hostfs_args - unsupported option - %s\n",
+				    options);
+		}
+		options = ptr;
+	}
+	return(0);
+}
+
+__uml_setup("hostfs=", hostfs_args,
+"hostfs=<root dir>,<flags>,...\n"
+"    This is used to set hostfs parameters.  The root directory argument\n"
+"    is used to confine all hostfs mounts to within the specified directory\n"
+"    tree on the host.  If this isn't specified, then a user inside UML can\n"
+"    mount anything on the host that's accessible to the user that's running\n"
+"    it.\n"
+"    The only flag currently supported is 'append', which specifies that all\n"
+"    files opened by hostfs will be opened in append mode.\n\n"
+);
+
 static char *dentry_name(struct dentry *dentry, int extra)
 {
 	struct dentry *parent;
@@ -274,7 +313,7 @@ int hostfs_file_open(struct inode *ino, struct file *file)
 	if(name == NULL) 
 		return(-ENOMEM);
 
-	fd = open_file(name, r, w);
+	fd = open_file(name, r, w, append);
 	kfree(name);
 	if(fd < 0) return(fd);
 	file_hostfs_i(file)->fd = fd;
@@ -363,6 +402,8 @@ int hostfs_readpage(struct file *file, struct page *page)
 			PAGE_CACHE_SIZE);
 	if(err < 0) goto out;
 
+	memset(&buffer[err], 0, PAGE_CACHE_SIZE - err);
+
 	flush_dcache_page(page);
 	SetPageUptodate(page);
 	if (PageError(page)) ClearPageError(page);
@@ -424,6 +465,7 @@ int hostfs_commit_write(struct file *file, struct page *page, unsigned from,
 static struct address_space_operations hostfs_aops = {
 	.writepage 	= hostfs_writepage,
 	.readpage	= hostfs_readpage,
+/* 	.set_page_dirty = __set_page_dirty_nobuffers, */
 	.prepare_write	= hostfs_prepare_write,
 	.commit_write	= hostfs_commit_write
 };
@@ -497,7 +539,7 @@ int hostfs_create(struct inode *dir, struct dentry *dentry, int mode)
 {
 	struct inode *inode;
 	char *name;
-	int error;
+	int error, fd;
 
 	inode = get_inode(dir->i_sb, dentry, &error);
 	if(error) return(error);
@@ -506,16 +548,21 @@ int hostfs_create(struct inode *dir, struct dentry *dentry, int mode)
 		iput(inode);
 		return(-ENOMEM);
 	}
-	error = file_create(name, 
-			    mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR, 
-			    mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP, 
-			    mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
-	if(!error) error = read_name(inode, name);
+	fd = file_create(name, 
+			 mode & S_IRUSR, mode & S_IWUSR, mode & S_IXUSR, 
+			 mode & S_IRGRP, mode & S_IWGRP, mode & S_IXGRP, 
+			 mode & S_IROTH, mode & S_IWOTH, mode & S_IXOTH);
+	if(fd < 0) 
+		error = fd;
+	else error = read_name(inode, name);
+
 	kfree(name);
 	if(error){
 		iput(inode);
 		return(error);
 	}
+	inode->u.hostfs_i.fd = fd;
+	inode->u.hostfs_i.mode = FMODE_READ | FMODE_WRITE;
 	d_instantiate(dentry, inode);
 	return(0);
 }
@@ -580,6 +627,9 @@ int hostfs_unlink(struct inode *ino, struct dentry *dentry)
 	int err;
 
 	if((file = inode_dentry_name(ino, dentry)) == NULL) return(-ENOMEM);
+	if(append)
+		return(-EPERM);
+
 	err = unlink_file(file);
 	kfree(file);
 	return(err);
@@ -687,6 +737,9 @@ int hostfs_setattr(struct dentry *dentry, struct iattr *attr)
 	struct hostfs_iattr attrs;
 	char *name;
 	int err;
+	
+	if(append) 
+		attr->ia_valid &= ~ATTR_SIZE;
 
 	attrs.ia_valid = 0;
 	if(attr->ia_valid & ATTR_MODE){
diff --git a/arch/um/fs/hostfs/hostfs_user.c b/arch/um/fs/hostfs/hostfs_user.c
index 97e40ac..48f3e4e 100644
--- a/arch/um/fs/hostfs/hostfs_user.c
+++ b/arch/um/fs/hostfs/hostfs_user.c
@@ -75,14 +75,20 @@ int access_file(char *path, int r, int w, int x)
 	else return(0);
 }
 
-int open_file(char *path, int r, int w)
+int open_file(char *path, int r, int w, int append)
 {
 	int mode = 0, fd;
 
-	if(r && !w) mode = O_RDONLY;
-	else if(!r && w) mode = O_WRONLY;
-	else if(r && w) mode = O_RDWR;
+	if(r && !w) 
+		mode = O_RDONLY;
+	else if(!r && w) 
+		mode = O_WRONLY;
+	else if(r && w) 
+		mode = O_RDWR;
 	else panic("Impossible mode in open_file");
+
+	if(append)
+		mode |= O_APPEND;
 	fd = open64(path, mode);
 	if(fd < 0) return(-errno);
 	else return(fd);
@@ -167,10 +173,10 @@ int file_create(char *name, int ur, int uw, int ux, int gr,
 	mode |= or ? S_IROTH : 0;
 	mode |= ow ? S_IWOTH : 0;
 	mode |= ox ? S_IXOTH : 0;
-	fd = open64(name, O_CREAT, mode);
-	if(fd < 0) return(-errno);
-	close(fd);
-	return(0);
+	fd = open64(name, O_CREAT | O_RDWR, mode);
+	if(fd < 0) 
+		return(-errno);
+	return(fd);
 }
 
 int set_attr(const char *file, struct hostfs_iattr *attrs)