1#@!#!123s

: / usr / share / systemtap / tapset / linux /
Filename : dentry.stp
back
// dentry tapset
// Copyright (c) 2009-2015 Red Hat Inc.
//
// This file is part of systemtap, and is free software.  You can
// redistribute it and/or modify it under the terms of the GNU General
// Public License (GPL); either version 2, or (at your option) any
// later version.
 

%{
// Make sure the filesystem "magic" constants we use are defined.
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,19))
#include <linux/magic.h>
#endif
#ifndef PIPEFS_MAGIC
#define PIPEFS_MAGIC            0x50495045
#endif
#ifndef SOCKFS_MAGIC
#define SOCKFS_MAGIC		0x534F434B
#endif
#ifndef ANON_INODE_FS_MAGIC
#define ANON_INODE_FS_MAGIC	0x09041934
#endif
#ifndef NSFS_MAGIC
#define NSFS_MAGIC		0x6e736673
#endif
%}

@__private30 function __dentry_IS_ROOT:long(dentry:long)
{
        return (@cast(dentry, "dentry")->d_parent == dentry)
}


@__private30 function __dentry_prepend:string(dentry:long,name:string)
{
        dname = d_name(dentry)

        /*
         * In case we are following down a mount point trigger, we can get
         * multiple instances of a root mount.
         */
        c = substr(name, strlen(name)-1, strlen(name)-1)
        if (dname == "/" && c == "/")
                return name;

        if (name == "") {
                return dname;
        } else {
                return sprintf("%s/%s", dname, name);
        }
}



/**
 *   sfunction d_name - get the dirent name
 *
 *   Returns the dirent name (path basename).
 *   @dentry: Pointer to dentry.
 */
function d_name:string(dentry:long)
{
        s = & @cast(dentry, "dentry")->d_name;
        return kernel_string_n(s->name, s->len);
}


@__private30 function __inode_first_dentry:long(inode:long)
{
        /* i_dentry is an hlist_head on 3.6+, or a list_head before that.  */
        d_alias = @choose_defined(
                        @cast(inode, "struct inode")->i_dentry->first,
                        @cast(inode, "struct inode")->i_dentry->next)

	if (@type_member_defined("struct dentry", d_alias)) {
        	return & @container_of(d_alias, "struct dentry", d_alias)
	}
	else {
        	return & @container_of(d_alias, "struct dentry", d_u->d_alias)
	}
}


@__private30 function __inode_vfsmount:long(inode:long)
{
        /* s_mounts was added in kernel 3.6, commit b3d9b7a3c.  */
        if (@type_member_defined("struct super_block", s_mounts)) {
                mnt_ns = @cast(task_current(), "struct task_struct")->nsproxy->mnt_ns
                sb = @cast(inode, "struct inode")->i_sb

                /* Look for the mount which matches the current namespace */
                head = &sb->s_mounts
                for (pos = head->next; pos != head; pos = pos->next) {
                        mount = & @container_of(pos, "struct mount", mnt_instance)
                        if (mount->mnt_ns == mnt_ns)
                                return & mount->mnt
                }
        }
        return 0
}


/**
 *   sfunction inode_name - get the inode name
 * 
 *   Returns the first path basename associated with the given inode.
 *   @inode: Pointer to inode.
 */
function inode_name:string(inode:long)
{
        return reverse_path_walk(__inode_first_dentry(inode))
}


/**
 *   sfunction inode_path - get the path to an inode
 * 
 *   Returns the full path associated with the given inode.
 *   @inode: Pointer to inode.
 */
function inode_path:string(inode:long)
{
        dentry = __inode_first_dentry(inode)
        vfsmount = __inode_vfsmount(inode)
        if (vfsmount != 0)
                return task_dentry_path(task_current(), dentry, vfsmount)

        /* This is not really a full path...  */
        return reverse_path_walk(dentry)
}


/**
 *   sfunction reverse_path_walk - get the full dirent path
 *
 *   Returns the path name (partial path to mount point).
 *   @dentry: Pointer to dentry.
 */
function reverse_path_walk:string(dentry:long)
{
        while(1) {
                name = __dentry_prepend(dentry, name);
                dentry = @cast(dentry, "dentry")->d_parent;
                if (__dentry_IS_ROOT(dentry))
                        return name;
        }
}


/**
 *   sfunction real_mount - get the 'struct mount' pointer
 *
 *   Returns the 'struct mount' pointer value for a 'struct vfsmount'
 *   pointer.
 *   @vfsmnt: Pointer to 'struct vfsmount'
 */
function real_mount:long(vfsmnt:long)
{
	if (@type_member_defined("mount", mnt_parent)) {
		/*
		 * The following is the script language equivalent of:
		 *
		 *    return container_of(vfsmnt, struct mount, mnt);
		 *
		 * We can't do the above because 'struct mount' is
		 * defined in a private header (in fs/mount.h).  But,
		 * we can do the script language equivalent (because
		 * we've got dwarf info).
		 *
		 * More spelled out in C, the above would look like:
		 *
		 *    return (vfsmnt - offsetof(struct mount, mnt));
                 *
                 * but here we're also making sure it won't wrap around.
		 */
		offset = @offsetof("mount", mnt)
		if (vfsmnt < 0 || vfsmnt > offset)
			return (vfsmnt - offset)
	}
	return 0
}

/**
 *   sfunction task_dentry_path - get the full dentry path
 *
 *   Returns the full dirent name (full path to the root), like
 *   the kernel d_path function.
 *   @task: task_struct pointer.
 *   @dentry: direntry pointer.
 *   @vfsmnt: vfsmnt pointer.
 */
function task_dentry_path:string(task:long,dentry:long,vfsmnt:long)
{
/*
 * Note that this function is based on __d_path() in RHEL6-era kernels
 * and prepend_path() in RHEL7+ kernels.
 */
	/*
	 * There are various synthetic filesystems that never get
	 * mounted. Filesystems needing to implement special "root
	 * names" do so with dentry->d_op->d_dname(). Unfortunately,
	 * it isn't really safe for us to call
	 * dentry->d_op->d_dname(). We can't really validate the
	 * function pointer or know that it can be called safely in
	 * the current context.
	 *
	 * Some pseudo inodes are mountable.  When they are mounted,
	 * dentry == vfsmnt->mnt_root.  In that case, we'll just go
	 * ahead and handle them normally.
	 */
	dentry = & @cast(dentry, "dentry")
	vfsmnt = & @cast(vfsmnt, "vfsmount")

	if (@type_member_defined("dentry", d_op->d_dname)
	    && dentry->d_op && dentry->d_op->d_dname
	    && (!__dentry_IS_ROOT(dentry) || dentry != vfsmnt->mnt_root)) {
		// The following code hits the majority of synthetic
		// filesystems that need special handling. As
		// mentioned earlier, we'd like to call d_dname()
		// here, but it isn't safe.
		if (vfsmnt->mnt_sb->s_magic == @const("SOCKFS_MAGIC")) {
			return sprintf("socket:[%lu]", dentry->d_inode->i_ino)
		}
		else if (vfsmnt->mnt_sb->s_magic == @const("PIPEFS_MAGIC")) {
			return sprintf("pipe:[%lu]", dentry->d_inode->i_ino)
		}
		else if (vfsmnt->mnt_sb->s_magic
			 == @const("ANON_INODE_FS_MAGIC")) {
			return sprintf("ANON_INODE:%s", d_name(dentry))
		}
		else if (vfsmnt->mnt_sb->s_magic == @const("NSFS_MAGIC")) {
			ns_ops = &@cast(dentry->d_fsdata, "proc_ns_operations")
			return sprintf("%s:[%lu]", kernel_string(ns_ops->name),
				       dentry->d_inode->i_ino)
		}
		return sprintf("UNKNOWN:[%p]", dentry)
	}

	# Handle old-school vs. new-school fs_structs.
	if (@type_member_defined("fs_struct", rootmnt)) {
		root_dentry = & @cast(task, "task_struct")->fs->root
		root_vfsmnt = & @cast(task, "task_struct")->fs->rootmnt
	}
	else {
		root_dentry = @cast(task, "task_struct")->fs->root->dentry
		root_vfsmnt = @cast(task, "task_struct")->fs->root->mnt
	}

	if (@type_member_defined("mount", mnt_parent)) {
		mnt = &@cast(real_mount(vfsmnt), "mount")
		if (mnt == 0)
			return "<unknown>"
	}

	# If we've found the right dentry/vfsmnt, we're done.
	while (dentry != root_dentry || vfsmnt == root_vfsmnt) {
		if (dentry == vfsmnt->mnt_root || __dentry_IS_ROOT(dentry)) {
			/* Escaped? */
			if (dentry != vfsmnt->mnt_root) {
				return "<unknown>"
			}

			/* RHEL7+ kernels */
			if (! @type_member_defined("vfsmount", mnt_parent)) {
				/* Global root? */
				if (mnt != mnt->mnt_parent) {
					dentry = mnt->mnt_mountpoint
					vfsmnt = & mnt->mnt_parent->mnt
					mnt = mnt->mnt_parent
					if (mnt == 0)
						return "<unknown>"
					continue
				}
				break
			}
			/* RHEL6-era kernels */
			else {
				/* Global root? */
				if (vfsmnt->mnt_parent == vfsmnt)
					return sprintf("%s%s",
						       d_name(vfsmnt->mnt_mountpoint),
						       name)

				dentry = vfsmnt->mnt_mountpoint
				vfsmnt = vfsmnt->mnt_parent
				continue
			}
		}
		name = __dentry_prepend(dentry, name)
		dentry = dentry->d_parent
	}

	return sprintf("/%s", name);
}



/**
 *   sfunction d_path - get the full nameidata path
 *
 *   Returns the full dirent name (full path to the root), like
 *   the kernel d_path function.
 *   @nd: Pointer to nameidata.
 */
function d_path:string(nd:long)
{
	dentry = @choose_defined(@cast(nd,"nameidata")->path->dentry,
			         @cast(nd,"nameidata")->dentry)
	vfsmnt = @choose_defined(@cast(nd,"nameidata")->path->mnt,
			         @cast(nd,"nameidata")->mnt)

	return sprintf("%s/", task_dentry_path(task_current(), dentry, vfsmnt))
}



/**
 *   sfunction fullpath_struct_nameidata - get the full nameidata path
 *
 *   Returns the full dirent name (full path to the root), like
 *   the kernel (and systemtap-tapset) d_path function, with a "/".
 *   @nd: Pointer to "struct nameidata".
 */
function fullpath_struct_nameidata(nd)
{
  return d_path(nd)
}


/**
 *   sfunction fullpath_struct_path - get the full path
 *
 *   Returns the full dirent name (full path to the root), like
 *   the kernel d_path function.
 *   @path: Pointer to "struct path".
 */
function fullpath_struct_path:string(path:long)
{
  return task_dentry_path(task_current(),
                          @cast(path,"path","kernel:nfs:kernel<linux/path.h>")->dentry,
                          @cast(path,"path","kernel:nfs:kernel<linux/path.h>")->mnt)
}

/**
 *   sfunction fullpath_struct_file - get the full path
 *
 *   Returns the full dirent name (full path to the root), like
 *   the kernel d_path function.
 *   @task: task_struct pointer.
 *   @file: Pointer to "struct file".
 */
function fullpath_struct_file:string(task:long, file:long)
{
  return task_dentry_path(task,
			  @choose_defined(@cast(file, "file")->f_path->dentry,
					  @cast(file, "file")->f_dentry),
			  @choose_defined(@cast(file, "file")->f_path->mnt,
					  @cast(file, "file")->f_vfsmnt))
}