Process Filesystem

Process filesystem. More...

Collaboration diagram for Process Filesystem:

Detailed Description

Process filesystem.

The "procfs" filesystem is used to expose process information and control interfaces to user space.

Each process has its own directory whose name is the process ID and for convenience, /self is a dynamic symbolic link to the current process's directory.

Unlike traditional UNIX systems, security is implemented such that a process can access all files of all processes that it could propagate mounts to, meaning any processes in its namespace or in child namespaces. If a process cant propagate mounts to a another process then certain entries will appear to not exist. This is implemented using the "revalidate()" dentry operation.

See also

Namespaces

Included below is a list of all entries found in each processes directory. All entries with restricted visibility will be marked with (restricted).

Note

Anytime a file descriptor is referred to it is from the perspective of the target process unless otherwise stated.

prio (restricted)

A readable and writable file that contains the scheduling priority of the process.

Format:

%llu

cwd (restricted)

A readable and writable file that contains the current working directory of the process.

Format:

%s

cmdline

A readable file that contains the command line arguments of the process (argv).

Format:

%s\0%s\0...%s\0

note (restricted)

A writable file that sends notes to the process. Writing to this file will enqueue that data as a note in the note queue of one of the process's threads.

See also

Notes

notegroup (restricted)

A writeable file that sends notes to every process in the group of the target process.

See also

Notes

group (restricted)

Opening this file returns a file descriptor referring to the group. This file descriptor can be used with the setgroup command in the ctl file to switch groups.

pid

A readable file that contains the process ID.

Format:

%llu

wait

A readable and pollable file that can be used to wait for the process to exit. Reading from this file will block until the process has exited.

The read value is the exit status of the process, usually either a integer exit code or a string describing the reason for termination often the note that caused it.

Format:

%s

perf

A readable file that contains performance statistics for the process.

Format:

user_clocks kernel_sched_clocks start_clocks user_pages thread_count
%llu %llu %llu %llu %llu

ns (restricted)

Opening this file returns a file descriptor referring to the namespace. This file descriptor can be used with the setns command in the ctl file to switch namespaces.

ctl (restricted)

A writable file that can be used to control certain aspects of the process, such as closing file descriptors.

Included is a list of all supported commands.

close <fd>

Closes the specified file descriptor in the process.

close <minfd> <maxfd>

Closes the range [minfd, maxfd) of file descriptors in the process.

Note that specifying -1 as maxfd will close all file descriptors from minfd to the maximum allowed file descriptor.

dup2 <oldfd> <newfd>

Duplicates the specified old file descriptor to the new file descriptor in the process.

bind <target> <source>

Bind a source path from the writing process to a target path in the processes namespace.

Path flags for controlling the bind behaviour should to be specified in the target path.

See also

Path for information on path flags.

mount <mountpoint> <fs> [device]

Mounts a filesystem at the specified mountpoint in the process's namespace, optionally with a device.

See also

Path for information on path flags.

touch <path>

Open the specified path in the process and immediately close it.

start

Starts the process if it was previously suspended.

kill [status]

Sends a kill note to all threads in the process, effectively terminating it. The optional status will be set as the processes exit status.

setns <fd>

Sets the namespace of the process to the one referred to by the file descriptor.

The file descriptor must be one that was opened from /[pid]/ns.

setgroup <fd>

Sets the group of the process to the one referred to by the file descriptor.

The file descriptor must be one that was opened from /[pid]/group.

env (restricted)

A directory that contains the environment variables of the process. Each environment variable is represented as a readable and writable file whose name is the name of the variable and whose content is the value of the variable.

To add or modify an environment variable, create or write to a file with the name of the variable. To remove an environment variable, delete the corresponding file.

Macros
#define	PROCFS_NAME   "procfs"
	Process filesystem name.

Functions
void	procfs_init (void)
	Register the procfs filesystem.

Macro Definition Documentation

PROCFS_NAME

#define PROCFS_NAME   "procfs"

Process filesystem name.

Definition at line 201 of file procfs.h.

Function Documentation

procfs_init()

void procfs_init

(

void

)

Register the procfs filesystem.

Definition at line 1267 of file procfs.c.

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