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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2012, 2013, 2014, 2017, 2019 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix 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.
;;;
;;; GNU Guix 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 GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (guix store roots)
#:use-module (guix config)
#:use-module ((guix store) #:select (store-path? %gc-roots-directory))
#:use-module (guix sets)
#:use-module (guix build syscalls)
#:use-module (srfi srfi-1)
#:use-module (srfi srfi-11)
#:use-module (srfi srfi-26)
#:use-module (ice-9 match)
#:use-module (ice-9 regex)
#:use-module (ice-9 rdelim)
#:use-module (ice-9 ftw)
#:use-module (rnrs io ports)
#:re-export (%gc-roots-directory)
#:export (gc-roots
user-owned?
busy-store-items))
;;; Commentary:
;;;
;;; This module provides tools to list and access garbage collector roots ("GC
;;; roots").
;;;
;;; Code:
(define %profile-directory
;; Directory where user profiles are stored.
;; XXX: This is redundant with the definition in (guix profiles) and not
;; entirely needed since in practice /var/guix/gcroots/profiles links to
;; it.
(string-append %state-directory "/profiles"))
(define (gc-roots)
"Return the list of garbage collector roots (\"GC roots\"). This includes
\"regular\" roots fount in %GC-ROOTS-DIRECTORY as well as indirect roots that
are user-controlled symlinks stored anywhere on the file system."
(define (regular? file)
(match file
(((or "." "..") . _) #f)
(_ #t)))
(define (file-type=? type)
(match-lambda
((file . properties)
(match (assq-ref properties 'type)
('unknown
(let ((stat (lstat file)))
(eq? type (stat:type stat))))
(actual-type
(eq? type actual-type))))))
(define directory?
(file-type=? 'directory))
(define symlink?
(file-type=? 'symlink))
(define canonical-root
(match-lambda
((file . properties)
(let ((target (readlink file)))
(cond ((store-path? target)
;; Regular root: FILE points to the store.
file)
;; Indirect root: FILE points to a user-controlled file outside
;; the store.
((string-prefix? "/" target)
target)
(else
(string-append (dirname file) "/" target)))))))
(let loop ((directories (list %gc-roots-directory
%profile-directory))
(roots '())
(visited (set)))
(match directories
(()
roots)
((directory . rest)
(if (set-contains? visited directory)
(loop rest roots visited)
(let*-values (((scope)
(cut string-append directory "/" <>))
((sub-directories files)
(partition directory?
(map (match-lambda
((file . properties)
(cons (scope file) properties)))
(scandir* directory regular?)))))
(loop (append rest (map first sub-directories))
(append (map canonical-root (filter symlink? files))
roots)
(set-insert directory visited))))))))
(define* (user-owned? root #:optional (uid (getuid)))
"Return true if ROOT exists and is owned by UID, false otherwise."
;; If ROOT is an indirect root, then perhaps it no longer exists. Thus,
;; catch 'system-error' exceptions.
(catch 'system-error
(lambda ()
(define stat
(lstat root))
(= (stat:uid stat) uid))
(const #f)))
;;;
;;; Listing "busy" store items: those referenced by currently running
;;; processes.
;;;
(define %proc-directory
;; Mount point of Linuxish /proc file system.
"/proc")
(define (proc-file-roots dir file)
"Return a one-element list containing the file pointed to by DIR/FILE,
or the empty list."
(or (and=> (false-if-exception (readlink (string-append dir "/" file)))
list)
'()))
(define proc-exe-roots (cut proc-file-roots <> "exe"))
(define proc-cwd-roots (cut proc-file-roots <> "cwd"))
(define (proc-fd-roots dir)
"Return the list of store files referenced by DIR, which is a
/proc/XYZ directory."
(let ((dir (string-append dir "/fd")))
(filter-map (lambda (file)
(let ((target (false-if-exception
(readlink (string-append dir "/" file)))))
(and target
(string-prefix? "/" target)
target)))
(or (scandir dir string->number) '()))))
(define (proc-maps-roots dir)
"Return the list of store files referenced by DIR, which is a
/proc/XYZ directory."
(define %file-mapping-line
(make-regexp "^.*[[:blank:]]+/([^ ]+)$"))
(call-with-input-file (string-append dir "/maps")
(lambda (maps)
(let loop ((line (read-line maps))
(roots '()))
(cond ((eof-object? line)
roots)
((regexp-exec %file-mapping-line line)
=>
(lambda (match)
(let ((file (string-append "/"
(match:substring match 1))))
(loop (read-line maps)
(cons file roots)))))
(else
(loop (read-line maps) roots)))))))
(define (proc-environ-roots dir)
"Return the list of store files referenced by DIR/environ, where DIR is a
/proc/XYZ directory."
(define split-on-nul
(cute string-tokenize <>
(char-set-complement (char-set #\nul))))
(define (rhs-file-names str)
(let ((equal (string-index str #\=)))
(if equal
(let* ((str (substring str (+ 1 equal)))
(rx (string-append (regexp-quote %store-directory)
"/[0-9a-z]{32}-[a-zA-Z0-9\\._+-]+")))
(map match:substring (list-matches rx str)))
'())))
(define environ
(string-append dir "/environ"))
(append-map rhs-file-names
(split-on-nul
(call-with-input-file environ
get-string-all))))
(define (referenced-files)
"Return the list of referenced store items."
(append-map (lambda (pid)
(let ((proc (string-append %proc-directory "/" pid)))
(catch 'system-error
(lambda ()
(append (proc-exe-roots proc)
(proc-cwd-roots proc)
(proc-fd-roots proc)
(proc-maps-roots proc)
(proc-environ-roots proc)))
(lambda args
(let ((err (system-error-errno args)))
(if (or (= ENOENT err) ;TOCTTOU race
(= ESRCH err) ;ditto
(= EACCES err)) ;not running as root
'()
(apply throw args)))))))
(scandir %proc-directory string->number
(lambda (a b)
(< (string->number a) (string->number b))))))
(define canonicalize-store-item
(let* ((store (string-append %store-directory "/"))
(prefix (string-length store)))
(lambda (file)
"Return #f if FILE is not a store item; otherwise, return the store file
name without any sub-directory components."
(and (string-prefix? store file)
(string-append store
(let ((base (string-drop file prefix)))
(match (string-index base #\/)
(#f base)
(slash (string-take base slash)))))))))
(define (busy-store-items)
"Return the list of store items used by the currently running processes.
This code should typically run as root; it allows the garbage collector to
determine which store items must not be deleted."
(delete-duplicates
(filter-map canonicalize-store-item (referenced-files))))
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