2007-09-10 Martin Hunt <hunt@redhat.com>

	* procfs.c: New file. Common runtime procfs functions.

1 files changed, 177 insertions, 0 deletions

diff --git a/runtime/procfs.c b/runtime/procfs.c
new file mode 100644
index 00000000..f31766ca
--- /dev/null
+++ b/runtime/procfs.c
@@ -0,0 +1,177 @@
+/* -*- linux-c -*-
+ *
+ * /proc command channels
+ * Copyright (C) 2007 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.
+ */
+
+/* The maximum number of files AND directories that can be opened.
+ * It would be great if the translator would emit this based on the actual
+ * number of needed files.
+ */
+
+#define STP_MAX_PROCFS_FILES 16
+static int _stp_num_pde = 0;
+static int _stp_num_procfs_files = 0;
+static struct proc_dir_entry *_stp_pde[STP_MAX_PROCFS_FILES];
+static struct proc_dir_entry *_stp_procfs_files[STP_MAX_PROCFS_FILES];
+static struct proc_dir_entry *_stp_proc_stap = NULL;
+static struct proc_dir_entry *_stp_proc_root = NULL;
+
+void _stp_close_procfs(void);
+
+/*
+ * Removes /proc/systemtap/{module_name} and /proc/systemtap (if empty)
+ */
+void _stp_rmdir_proc_module(void)
+{
+        if (_stp_proc_root && _stp_proc_root->subdir == NULL) {
+		remove_proc_entry(THIS_MODULE->name, _stp_proc_stap);
+		_stp_proc_root = NULL;
+	}
+
+	if (_stp_proc_stap) {
+		if (!_stp_lock_debugfs()) {
+			errk("Unable to lock transport directory.\n");
+			return;
+		}
+
+		if (_stp_proc_stap->subdir == NULL) {
+			remove_proc_entry("systemtap", NULL);
+			_stp_proc_stap = NULL;
+		}
+
+		_stp_unlock_debugfs();
+	}
+}
+
+
+/*
+ * Safely creates /proc/systemtap (if necessary) and
+ * /proc/systemtap/{module_name}.
+ */
+int _stp_mkdir_proc_module(void)
+{	
+        if (_stp_proc_root == NULL) {
+		struct nameidata nd;
+
+		if (!_stp_lock_debugfs()) {
+			errk("Unable to lock transport directory.\n");
+			goto done;
+		}
+		
+		/* We use path_lookup() because there is no lookup */
+		/* function for procfs we can call directly.  And */
+		/* proc_mkdir() will always succeed, creating multiple */
+		/* directory entries, all with the same name. */
+
+		if (path_lookup("/proc/systemtap", 0, &nd)) {
+			/* doesn't exist, so create it */
+			_stp_proc_stap = proc_mkdir ("systemtap", NULL);
+			if (_stp_proc_stap == NULL) {
+				_stp_unlock_debugfs();
+				goto done;
+			}
+		} else
+			_stp_proc_stap = PDE(nd.dentry->d_inode);
+
+		_stp_proc_root = proc_mkdir(THIS_MODULE->name, _stp_proc_stap);
+		_stp_unlock_debugfs();
+	}
+done:
+	return (_stp_proc_root) ? 1 : 0;
+}
+
+/*
+ * This checks our local cache to see if we already made the dir.
+ */
+static struct proc_dir_entry *_stp_procfs_dir_lookup(char *dir, struct proc_dir_entry *parent)
+{
+	int i;
+	for (i = 0; i <_stp_num_pde; i++) {
+		struct proc_dir_entry *pde = _stp_pde[i];
+		if (pde->parent == parent && !strcmp(dir, pde->name))
+			return pde;
+	}
+	return NULL;
+}
+
+int _stp_create_procfs(char *path, int num)
+{  
+	char *p = path, *next;
+	struct proc_dir_entry *last_dir, *de;
+
+	if (num >= STP_MAX_PROCFS_FILES) {
+		_stp_error("Requested file number %d is larger than max (%d)\n", 
+			   num, STP_MAX_PROCFS_FILES);
+		return -1;
+	}
+	
+	_stp_mkdir_proc_module();
+	last_dir = _stp_proc_root;
+
+	/* if no path, use default one */
+	if (strlen(p) == 0)
+		p = "command";
+	_dbug("path=/proc/systemtap/%s/%s\n", THIS_MODULE->name, p);
+	
+	while ((next = strchr(p, '/'))) {
+		if (_stp_num_pde == STP_MAX_PROCFS_FILES)
+			goto too_many;
+		*next = 0;
+		de = _stp_procfs_dir_lookup(p, last_dir);
+		_dbug("lookup of %s %p returned %p\n", p, last_dir, de);
+		if (de == NULL) {
+			    last_dir = proc_mkdir(p, last_dir);
+			    if (!last_dir) {
+				    _stp_error("Could not create directory \"%s\" " \
+					       "in path \"%s\"\n", p, path);
+				    goto err;
+			    }
+			    _dbug("mkdir %s returned %p\n", p, last_dir);
+			    _stp_pde[_stp_num_pde++] = last_dir;
+			    last_dir->uid = _stp_uid;
+			    last_dir->gid = _stp_gid;
+		} else
+			last_dir = de;
+		p = next + 1;
+	}
+	
+	if (_stp_num_pde == STP_MAX_PROCFS_FILES)
+		goto too_many;
+	
+	_dbug("creating file %s\n", p);
+	de = create_proc_entry (p, 0600, last_dir);
+	if (de == NULL) {
+		_stp_error("Could not create file \"%s\" in path \"%s\"\n", p, path);
+		goto err;
+	}
+	_stp_pde[_stp_num_pde++] = de;
+	_stp_procfs_files[num] = de;
+	de->uid = _stp_uid;
+	de->gid = _stp_gid;
+	return 0;
+	
+too_many:
+	_stp_error("Attempted to open too many procfs files. Maximum is %d\n", STP_MAX_PROCFS_FILES);
+err:
+	_stp_close_procfs();
+	return -1;
+}
+
+void _stp_close_procfs(void)
+{
+	int i;
+	_dbug("closing all procfs files\n");
+	for (i = _stp_num_pde-1; i >= 0; i--) {
+		struct proc_dir_entry *pde = _stp_pde[i];
+		_dbug("remove %s in %s\n", pde->name, pde->parent->name);
+		remove_proc_entry(pde->name, pde->parent);
+	}
+	_stp_num_pde = 0;
+	_stp_rmdir_proc_module();
+}