CasperSecurity
;;; Dynamically linking foreign libraries via dlopen and dlsym
;;; Copyright (C) 2021 Free Software Foundation, Inc.
;;;
;;; This library is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU Lesser General Public License as
;;; published by the Free Software Foundation, either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; This library 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
;;; Lesser General Public License for more details.
;;;
;;; You should have received a copy of the GNU Lesser General Public
;;; License along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;;
;;; Implementation of dynamic-link.
;;;
;;; Code:
(define-module (system foreign-library)
#:use-module (ice-9 match)
#:use-module (srfi srfi-9)
#:use-module (system foreign)
#:export (guile-extensions-path
ltdl-library-path
guile-system-extensions-path
lib->cyg
load-foreign-library
foreign-library?
foreign-library-pointer
foreign-library-function))
(define-record-type <foreign-library>
(make-foreign-library filename handle)
foreign-library?
(filename foreign-library-filename)
(handle foreign-library-handle set-foreign-library-handle!))
(eval-when (expand load eval)
(load-extension (string-append "libguile-" (effective-version))
"scm_init_system_foreign_library"))
(define system-library-extensions
(cond
((string-contains %host-type "-darwin-")
'(".bundle" ".so" ".dylib"))
((or (string-contains %host-type "cygwin")
(string-contains %host-type "mingw")
(string-contains %host-type "msys"))
'(".dll"))
(else
'(".so"))))
(define (has-extension? head exts)
(match exts
(() #f)
((ext . exts)
(or (string-contains head ext)
(has-extension? head exts)))))
(define (file-exists-with-extension head exts)
(if (has-extension? head exts)
(and (file-exists? head) head)
(let lp ((exts exts))
(match exts
(() #f)
((ext . exts)
(let ((head (string-append head ext)))
(if (file-exists? head)
head
(lp exts))))))))
(define (file-exists-in-path-with-extension basename path exts)
(match path
(() #f)
((dir . path)
(or (file-exists-with-extension (in-vicinity dir basename) exts)
(file-exists-in-path-with-extension basename path exts)))))
(define path-separator
(case (system-file-name-convention)
((posix) #\:)
((windows) #\;)
(else (error "unreachable"))))
(define (parse-path var)
(match (getenv var)
(#f #f)
;; Ignore e.g. "export GUILE_SYSTEM_EXTENSIONS_PATH=".
("" '())
(val (string-split val path-separator))))
(define guile-extensions-path
(make-parameter
(or (parse-path "GUILE_EXTENSIONS_PATH") '())))
(define ltdl-library-path
(make-parameter
(or (parse-path "LTDL_LIBRARY_PATH") '())))
(define guile-system-extensions-path
(make-parameter
(or (parse-path "GUILE_SYSTEM_EXTENSIONS_PATH")
(list (assq-ref %guile-build-info 'libdir)
(assq-ref %guile-build-info 'extensiondir)))))
;; There are a few messy situations here related to libtool.
;;
;; Guile used to use libltdl, the dynamic library loader provided by
;; libtool. This loader used LTDL_LIBRARY_PATH, and for backwards
;; compatibility we still support that path.
;;
;; However, libltdl would not only open ".so" (or ".dll", etc) files,
;; but also the ".la" files created by libtool. In installed libraries
;; -- libraries that are in the target directories of "make install" --
;; .la files are never needed, to the extent that most GNU/Linux
;; distributions remove them entirely. It is sufficient to just load
;; the ".so" (or ".dll", etc) files.
;;
;; But for uninstalled dynamic libraries, like those in a build tree, it
;; is a bit of a mess. If you have a project that uses libtool to build
;; libraries -- which is the case for Guile, and for most projects using
;; autotools -- and you build foo.so in directory D, libtool will put
;; foo.la in D, but foo.so goes in D/.libs.
;;
;; The nice thing about ltdl was that it could load the .la file, even
;; from a build tree, preventing the existence of ".libs" from leaking
;; out to the user.
;;
;; We don't use libltdl now, essentially for flexibility and
;; error-reporting reasons. But, it would be nice to keep this old
;; use-case working. So as a stopgap solution, we add a ".libs" subdir
;; to the path for each entry in LTDL_LIBRARY_PATH, in case the .so is
;; there instead of alongside the .la file.
(define (augment-ltdl-library-path path)
(match path
(() '())
((dir . path)
(cons* dir (in-vicinity dir ".libs")
(augment-ltdl-library-path path)))))
(define (default-search-path search-ltdl-library-path?)
(append
(guile-extensions-path)
(if search-ltdl-library-path?
(augment-ltdl-library-path (ltdl-library-path))
'())
(guile-system-extensions-path)))
(define (lib->cyg name)
"Convert a standard shared library name to a Cygwin shared library
name."
(if (not name)
#f
(let ((start (1+ (or (string-index-right
name
(lambda (c) (or (char=? #\\ c) (char=? #\/ c))))
-1))))
(cond
((>= (+ 3 start) (string-length name))
name)
((string= name "lib" start (+ start 3))
(string-append (substring name 0 start)
"cyg"
(substring name (+ start 3))))
(else
name)))))
(define* (load-foreign-library #:optional filename #:key
(extensions system-library-extensions)
(search-ltdl-library-path? #t)
(search-path (default-search-path
search-ltdl-library-path?))
(search-system-paths? #t)
(lazy? #t) (global? #f) (rename-on-cygwin? #t))
(define (error-not-found)
(scm-error 'misc-error "load-foreign-library"
"file: ~S, message: ~S"
(list filename "file not found")
#f))
(define flags
(logior (if lazy? RTLD_LAZY RTLD_NOW)
(if global? RTLD_GLOBAL RTLD_LOCAL)))
(define (dlopen* name) (dlopen name flags))
(if (and rename-on-cygwin? (string-contains %host-type "cygwin"))
(set! filename (lib->cyg filename)))
(make-foreign-library
filename
(cond
((not filename)
;; The self-open trick.
(dlopen* #f))
((or (absolute-file-name? filename)
(string-any file-name-separator? filename))
(cond
((or (file-exists-with-extension filename extensions)
(and search-ltdl-library-path?
(file-exists-with-extension
(in-vicinity (in-vicinity (dirname filename) ".libs")
(basename filename))
extensions)))
=> dlopen*)
(else
(error-not-found))))
((file-exists-in-path-with-extension filename search-path extensions)
=> dlopen*)
(search-system-paths?
(if (or (null? extensions) (has-extension? filename extensions))
(dlopen* filename)
(let lp ((extensions extensions))
(match extensions
((extension)
;; Open in tail position to propagate any exception.
(dlopen* (string-append filename extension)))
((extension . extensions)
;; If there is more than one extension, unfortunately we
;; only report the error for the last extension. This is
;; not great because maybe the library was found with the
;; first extension, failed to load and had an interesting
;; error, but then we swallowed that interesting error and
;; proceeded, eventually throwing a "file not found"
;; exception. FIXME to use more structured exceptions and
;; stop if the error that we get is more specific than
;; just "file not found".
(or (false-if-exception
(dlopen* (string-append filename extension)))
(lp extensions)))))))
(else
(error-not-found)))))
(define (->foreign-library lib)
(if (foreign-library? lib)
lib
(load-foreign-library lib)))
(define* (foreign-library-pointer lib name)
(let ((handle (foreign-library-handle (->foreign-library lib))))
(dlsym handle name)))
(define* (foreign-library-function lib name
#:key
(return-type void)
(arg-types '())
(return-errno? #f))
(let ((pointer (foreign-library-pointer lib name)))
(pointer->procedure return-type pointer arg-types
#:return-errno? return-errno?)))