254 lines
9.2 KiB
Scheme
254 lines
9.2 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2012-2014, 2017, 2019, 2023 Ludovic Courtès <ludo@gnu.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (guix store roots)
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#:use-module (guix config)
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#:use-module ((guix store) #:select (store-path? %gc-roots-directory))
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#:use-module (guix sets)
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#:use-module (guix build syscalls)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-11)
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#:use-module (srfi srfi-26)
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#:use-module (ice-9 match)
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#:use-module (ice-9 regex)
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#:use-module (ice-9 rdelim)
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#:use-module (ice-9 ftw)
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#:use-module (rnrs io ports)
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#:re-export (%gc-roots-directory)
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#:export (gc-roots
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user-owned?
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busy-store-items))
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;;; Commentary:
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;;;
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;;; This module provides tools to list and access garbage collector roots ("GC
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;;; roots").
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;;;
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;;; Code:
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(define %profile-directory
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;; Directory where user profiles are stored.
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;; XXX: This is redundant with the definition in (guix profiles) and not
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;; entirely needed since in practice /var/guix/gcroots/profiles links to
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;; it.
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(string-append %state-directory "/profiles"))
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(define (gc-roots)
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"Return the list of garbage collector roots (\"GC roots\"). This includes
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\"regular\" roots found in %GC-ROOTS-DIRECTORY as well as indirect roots that
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are user-controlled symlinks stored anywhere on the file system."
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(define (regular? file)
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(match file
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(((or "." "..") . _) #f)
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(_ #t)))
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(define (file-type=? type)
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(match-lambda
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((file . properties)
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(match (assq-ref properties 'type)
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('unknown
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(let ((stat (lstat file)))
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(eq? type (stat:type stat))))
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(actual-type
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(eq? type actual-type))))))
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(define directory?
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(file-type=? 'directory))
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(define symlink?
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(file-type=? 'symlink))
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(define canonical-root
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(match-lambda
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((file . properties)
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(let ((target (readlink file)))
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(cond ((store-path? target)
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;; Regular root: FILE points to the store.
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file)
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;; Indirect root: FILE points to a user-controlled file outside
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;; the store.
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((string-prefix? "/" target)
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target)
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(else
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(string-append (dirname file) "/" target)))))))
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(let loop ((directories (list %gc-roots-directory
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%profile-directory))
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(roots '())
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(visited (set)))
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(match directories
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(()
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roots)
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((directory . rest)
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(if (set-contains? visited directory)
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(loop rest roots visited)
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(let*-values (((scope)
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(cut string-append directory "/" <>))
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((sub-directories files)
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(partition directory?
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(map (match-lambda
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((file . properties)
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(cons (scope file) properties)))
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(catch 'system-error
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(lambda ()
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(scandir* directory regular?))
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(lambda args
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(if (= ENOENT
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(system-error-errno
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args))
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'()
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(apply throw args))))))))
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(loop (append rest (map first sub-directories))
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(append (map canonical-root (filter symlink? files))
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roots)
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(set-insert directory visited))))))))
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(define* (user-owned? root #:optional (uid (getuid)))
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"Return true if ROOT exists and is owned by UID, false otherwise."
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;; If ROOT is an indirect root, then perhaps it no longer exists. Thus,
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;; catch 'system-error' exceptions.
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(catch 'system-error
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(lambda ()
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(define stat
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(lstat root))
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(= (stat:uid stat) uid))
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(const #f)))
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;;;
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;;; Listing "busy" store items: those referenced by currently running
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;;; processes.
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;;;
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(define %proc-directory
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;; Mount point of Linuxish /proc file system.
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"/proc")
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(define (proc-file-roots dir file)
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"Return a one-element list containing the file pointed to by DIR/FILE,
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or the empty list."
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(or (and=> (false-if-exception (readlink (string-append dir "/" file)))
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list)
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'()))
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(define proc-exe-roots (cut proc-file-roots <> "exe"))
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(define proc-cwd-roots (cut proc-file-roots <> "cwd"))
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(define (proc-fd-roots dir)
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"Return the list of store files referenced by DIR, which is a
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/proc/XYZ directory."
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(let ((dir (string-append dir "/fd")))
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(filter-map (lambda (file)
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(let ((target (false-if-exception
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(readlink (string-append dir "/" file)))))
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(and target
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(string-prefix? "/" target)
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target)))
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(or (scandir dir string->number) '()))))
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(define (proc-maps-roots dir)
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"Return the list of store files referenced by DIR, which is a
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/proc/XYZ directory."
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(define %file-mapping-line
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(make-regexp "^.*[[:blank:]]+/([^ ]+)$"))
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(call-with-input-file (string-append dir "/maps")
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(lambda (maps)
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(let loop ((line (read-line maps))
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(roots '()))
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(cond ((eof-object? line)
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roots)
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((regexp-exec %file-mapping-line line)
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=>
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(lambda (match)
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(let ((file (string-append "/"
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(match:substring match 1))))
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(loop (read-line maps)
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(cons file roots)))))
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(else
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(loop (read-line maps) roots)))))))
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(define (proc-environ-roots dir)
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"Return the list of store files referenced by DIR/environ, where DIR is a
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/proc/XYZ directory."
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(define split-on-nul
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(cute string-tokenize <>
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(char-set-complement (char-set #\nul))))
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(define (rhs-file-names str)
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(let ((equal (string-index str #\=)))
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(if equal
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(let* ((str (substring str (+ 1 equal)))
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(rx (string-append (regexp-quote %store-directory)
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"/[0-9a-z]{32}-[a-zA-Z0-9\\._+-]+")))
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(map match:substring (list-matches rx str)))
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'())))
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(define environ
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(string-append dir "/environ"))
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(append-map rhs-file-names
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(split-on-nul
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(call-with-input-file environ
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get-string-all))))
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(define (referenced-files)
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"Return the list of referenced store items."
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(append-map (lambda (pid)
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(let ((proc (string-append %proc-directory "/" pid)))
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(catch 'system-error
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(lambda ()
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(append (proc-exe-roots proc)
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(proc-cwd-roots proc)
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(proc-fd-roots proc)
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(proc-maps-roots proc)
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(proc-environ-roots proc)))
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(lambda args
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(let ((err (system-error-errno args)))
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(if (or (= ENOENT err) ;TOCTTOU race
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(= ESRCH err) ;ditto
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(= EACCES err)) ;not running as root
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'()
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(apply throw args)))))))
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(scandir %proc-directory string->number
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(lambda (a b)
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(< (string->number a) (string->number b))))))
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(define canonicalize-store-item
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(let* ((store (string-append %store-directory "/"))
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(prefix (string-length store)))
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(lambda (file)
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"Return #f if FILE is not a store item; otherwise, return the store file
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name without any sub-directory components."
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(and (string-prefix? store file)
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(string-append store
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(let ((base (string-drop file prefix)))
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(match (string-index base #\/)
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(#f base)
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(slash (string-take base slash)))))))))
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(define (busy-store-items)
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"Return the list of store items used by the currently running processes.
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This code should typically run as root; it allows the garbage collector to
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determine which store items must not be deleted."
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(delete-duplicates
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(filter-map canonicalize-store-item (referenced-files))))
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