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+#!@BASH@
+# -*- mode: scheme; coding: utf-8; -*-
+
+# XXX: We have to go through Bash because there's no command-line switch to
+# augment %load-compiled-path, and because of the silly 127-byte limit for
+# the shebang line in Linux.
+# Use `load-compiled' because `load' (and `-l') doesn't otherwise load our
+# .go file (see <http://bugs.gnu.org/12519>).
+# Unset 'GUILE_LOAD_COMPILED_PATH' to make sure we do not stumble upon
+# incompatible .go files. See
+# <https://lists.gnu.org/archive/html/guile-devel/2016-03/msg00000.html>.
+
+unset GUILE_LOAD_COMPILED_PATH
+main="(@ (gnu build-support ld-wrapper) ld-wrapper)"
+exec @GUILE@ -c "(load-compiled \"@SELF@.go\") (apply $main (cdr (command-line)))" "$@"
+!#
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2020 Marius Bakke <mbakke@fastmail.com>
+;;;
+;;; 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 (gnu build-support ld-wrapper)
+ #:use-module (srfi srfi-1)
+ #:use-module (ice-9 match)
+ #:autoload (ice-9 rdelim) (read-delimited)
+ #:export (ld-wrapper))
+
+;;; Commentary:
+;;;
+;;; This is a wrapper for the linker. Its purpose is to inspect the -L and
+;;; -l switches passed to the linker, add corresponding -rpath arguments, and
+;;; invoke the actual linker with this new set of arguments.
+;;;
+;;; The alternatives to this hack would be:
+;;;
+;;; 1. Using $LD_RUN_PATH. However, that would tend to include more than
+;;; needed in the RPATH; for instance, given a package with `libfoo' as
+;;; an input, all its binaries would have libfoo in their RPATH,
+;;; regardless of whether they actually NEED it.
+;;;
+;;; 2. Use a GCC "lib" spec string such as `%{L*:-rpath %*}', which adds a
+;;; `-rpath LIBDIR' argument for each occurrence of `-L LIBDIR'.
+;;; However, this doesn't work when $LIBRARY_PATH is used, because the
+;;; additional `-L' switches are not matched by the above rule, because
+;;; the rule only matches explicit user-provided switches. See
+;;; <http://gcc.gnu.org/ml/gcc-help/2012-09/msg00110.html> for details.
+;;;
+;;; As a bonus, this wrapper checks for "impurities"--i.e., references to
+;;; libraries outside the store.
+;;;
+;;; Code:
+
+(define %real-ld
+ ;; Name of the linker that we wrap.
+ "@LD@")
+
+(define %store-directory
+ ;; File name of the store.
+ (or (getenv "NIX_STORE") "/gnu/store"))
+
+(define %temporary-directory
+ ;; Temporary directory.
+ (or (getenv "TMPDIR") "/tmp"))
+
+(define %build-directory
+ ;; Top build directory when run from a builder.
+ (getenv "NIX_BUILD_TOP"))
+
+(define %allow-impurities?
+ ;; Whether to allow references to libraries outside the store.
+ ;; Allow them by default for convenience.
+ (let ((value (getenv "GUIX_LD_WRAPPER_ALLOW_IMPURITIES")))
+ (or (not value)
+ (let ((value (string-downcase value)))
+ (cond ((member value '("yes" "y" "t" "true" "1"))
+ #t)
+ ((member value '("no" "n" "f" "false" "0"))
+ #f)
+ (else
+ (format (current-error-port)
+ "ld-wrapper: ~s: invalid value for \
+'GUIX_LD_WRAPPER_ALLOW_IMPURITIES'~%"
+ value)))))))
+
+(define %debug?
+ ;; Whether to emit debugging output.
+ (getenv "GUIX_LD_WRAPPER_DEBUG"))
+
+(define %disable-rpath?
+ ;; Whether to disable automatic '-rpath' addition.
+ (getenv "GUIX_LD_WRAPPER_DISABLE_RPATH"))
+
+(define (readlink* file)
+ ;; Call 'readlink' until the result is not a symlink.
+ (define %max-symlink-depth 50)
+
+ (let loop ((file file)
+ (depth 0))
+ (define (absolute target)
+ (if (absolute-file-name? target)
+ target
+ (string-append (dirname file) "/" target)))
+
+ (if (>= depth %max-symlink-depth)
+ file
+ (call-with-values
+ (lambda ()
+ (catch 'system-error
+ (lambda ()
+ (values #t (readlink file)))
+ (lambda args
+ (let ((errno (system-error-errno args)))
+ (if (or (= errno EINVAL) (= errno ENOENT))
+ (values #f file)
+ (apply throw args))))))
+ (lambda (success? target)
+ (if success?
+ (loop (absolute target) (+ depth 1))
+ file))))))
+
+(define (pure-file-name? file)
+ ;; Return #t when FILE is the name of a file either within the store
+ ;; (possibly via a symlink) or within the build directory.
+ (let ((file (readlink* file)))
+ (or (not (string-prefix? "/" file))
+ (string-prefix? %store-directory file)
+ (string-prefix? %temporary-directory file)
+ (and %build-directory
+ (string-prefix? %build-directory file)))))
+
+(define (store-file-name? file)
+ ;; Return #t when FILE is a store file, possibly indirectly.
+ (string-prefix? %store-directory (readlink* file)))
+
+(define (shared-library? file)
+ ;; Return #t when FILE denotes a shared library.
+ (or (string-suffix? ".so" file)
+ (let ((index (string-contains file ".so.")))
+ ;; Since we cannot use regexps during bootstrap, roll our own.
+ (and index
+ (string-every (char-set-union (char-set #\.) char-set:digit)
+ (string-drop file (+ index 3)))))))
+
+(define (library-search-path args)
+ ;; Return the library search path as a list of directory names. The GNU ld
+ ;; manual notes that "[a]ll `-L' options apply to all `-l' options,
+ ;; regardless of the order in which the options appear", so we must compute
+ ;; the search path independently of the -l options.
+ (let loop ((args args)
+ (path '()))
+ (match args
+ (()
+ (reverse path))
+ (("-L" directory . rest)
+ (loop rest (cons directory path)))
+ ((argument . rest)
+ (if (string-prefix? "-L" argument) ;augment the search path
+ (loop rest
+ (cons (string-drop argument 2) path))
+ (loop rest path))))))
+
+(define (library-files-linked args library-path)
+ ;; Return the absolute file names of shared libraries explicitly linked
+ ;; against via `-l' or with an absolute file name in ARGS, looking them up
+ ;; in LIBRARY-PATH.
+ (define files+args
+ (fold (lambda (argument result)
+ (match result
+ ((library-files ((and flag
+ (or "-dynamic-linker" "-plugin"))
+ . rest))
+ ;; When passed '-dynamic-linker ld.so', ignore 'ld.so'; when
+ ;; passed '-plugin liblto_plugin.so', ignore
+ ;; 'liblto_plugin.so'. See <http://bugs.gnu.org/20102>.
+ (list library-files
+ (cons* argument flag rest)))
+ ((library-files previous-args)
+ (cond ((string-prefix? "-l" argument) ;add library
+ (let* ((lib (string-append "lib"
+ (string-drop argument 2)
+ ".so"))
+ (full (search-path library-path lib)))
+ (list (if full
+ (cons full library-files)
+ library-files)
+ (cons argument previous-args))))
+ ((and (string-prefix? %store-directory argument)
+ (shared-library? argument)) ;add library
+ (list (cons argument library-files)
+ (cons argument previous-args)))
+ (else
+ (list library-files
+ (cons argument previous-args)))))))
+ (list '() '())
+ args))
+
+ (match files+args
+ ((files arguments)
+ (reverse files))))
+
+(define (rpath-arguments library-files)
+ ;; Return the `-rpath' argument list for each of LIBRARY-FILES, a list of
+ ;; absolute file names.
+ (fold-right (lambda (file args)
+ ;; Add '-rpath' if and only if FILE is in the store; we don't
+ ;; want to add '-rpath' for files under %BUILD-DIRECTORY or
+ ;; %TEMPORARY-DIRECTORY because that could leak to installed
+ ;; files.
+ (cond ((and (not %disable-rpath?)
+ (store-file-name? file))
+ (cons* "-rpath" (dirname file) args))
+ ((or %allow-impurities?
+ (pure-file-name? file))
+ args)
+ (else
+ (begin
+ (format (current-error-port)
+ "ld-wrapper: error: attempt to use \
+library outside of ~a: ~s~%"
+ %store-directory file)
+ (exit 1)))))
+ '()
+ library-files))
+
+(define (expand-arguments args)
+ ;; Expand ARGS such that "response file" arguments, such as "@args.txt", are
+ ;; expanded (info "(gcc) Overall Options").
+ (define (response-file-arguments file)
+ (define (tokenize port)
+ ;; Return a list of all strings found in PORT. Quote characters are removed,
+ ;; but whitespaces within quoted strings are preserved.
+ (let loop ((words '()))
+ (let* ((word (read-delimited " '\"" port 'split))
+ (token (car word))
+ (delim (cdr word)))
+ (if (eof-object? delim)
+ (reverse words)
+ (case delim
+ ((#\") (loop (cons (read-delimited "\"" port) words)))
+ ((#\') (loop (cons (read-delimited "'" port) words)))
+ ((#\ ) (if (> 0 (string-length token))
+ (loop (cons token words))
+ (loop words)))
+ (else (loop words)))))))
+
+ (when %debug?
+ (format (current-error-port)
+ "ld-wrapper: attempting to read arguments from '~a'~%" file))
+
+ (call-with-input-file file tokenize))
+
+ (define result
+ (fold-right (lambda (arg result)
+ (if (string-prefix? "@" arg)
+ (let ((file (string-drop arg 1)))
+ (append (catch 'system-error
+ (lambda ()
+ (response-file-arguments file))
+ (lambda args
+ ;; FILE doesn't exist or cannot be read so
+ ;; leave ARG as is.
+ (list arg)))
+ result))
+ (cons arg result)))
+ '()
+ args))
+
+ ;; If there are "@" arguments in RESULT *and* we can expand them (they don't
+ ;; refer to nonexistent files), then recurse.
+ (if (equal? result args)
+ result
+ (expand-arguments result)))
+
+(define (ld-wrapper . args)
+ ;; Invoke the real `ld' with ARGS, augmented with `-rpath' switches.
+ (let* ((args (expand-arguments args))
+ (path (library-search-path args))
+ (libs (library-files-linked args path))
+ (args (append args (rpath-arguments libs))))
+ (when %debug?
+ (format (current-error-port)
+ "ld-wrapper: library search path: ~s~%" path)
+ (format (current-error-port)
+ "ld-wrapper: libraries linked: ~s~%" libs)
+ (format (current-error-port)
+ "ld-wrapper: invoking `~a' with ~s~%"
+ %real-ld args)
+ (force-output (current-error-port)))
+ (apply execl %real-ld (basename %real-ld) args)))
+
+;;; ld-wrapper.scm ends here
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