Add (guix build gremlin).

* guix/build/gremlin.scm, tests/gremlin.scm: New files.
* Makefile.am (MODULES): Add guix/build/gremlin.scm.
  (SCM_TESTS): Add tests/gremlin.scm.

1 files changed, 236 insertions, 0 deletions

diff --git a/guix/build/gremlin.scm b/guix/build/gremlin.scm
new file mode 100644
index 0000000000..e8429129e1
--- /dev/null
+++ b/guix/build/gremlin.scm
@@ -0,0 +1,236 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2015 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 build gremlin)
+  #:use-module (guix elf)
+  #:use-module (ice-9 match)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-9)
+  #:use-module (srfi srfi-26)
+  #:use-module (system foreign)
+  #:use-module (rnrs bytevectors)
+  #:use-module (rnrs io ports)
+  #:export (elf-dynamic-info
+            elf-dynamic-info?
+            elf-dynamic-info-sopath
+            elf-dynamic-info-needed
+            elf-dynamic-info-rpath
+            elf-dynamic-info-runpath
+
+            validate-needed-in-runpath))
+
+;;; Commentary:
+;;;
+;;; A gremlin is sort-of like an elf, you know, and this module provides tools
+;;; to deal with dynamic-link information from ELF files.
+;;;
+;;; Code:
+
+(define (dynamic-link-segment elf)
+  "Return the 'PT_DYNAMIC' segment of ELF--i.e., the segment that contains
+dynamic linking information."
+  (find (lambda (segment)
+          (= (elf-segment-type segment) PT_DYNAMIC))
+        (elf-segments elf)))
+
+(define (word-reader size byte-order)
+  "Return a procedure to read a word of SIZE bytes according to BYTE-ORDER."
+  (case size
+    ((8)
+     (lambda (bv index)
+       (bytevector-u64-ref bv index byte-order)))
+    ((4)
+     (lambda (bv index)
+       (bytevector-u32-ref bv index byte-order)))))
+
+
+;; Dynamic entry:
+;;
+;; typedef struct
+;; {
+;;   Elf64_Sxword       d_tag;   /* Dynamic entry type */
+;;   union
+;;     {
+;;       Elf64_Xword d_val;      /* Integer value */
+;;       Elf64_Addr d_ptr;       /* Address value */
+;;     } d_un;
+;; } Elf64_Dyn;
+
+(define (raw-dynamic-entries elf segment)
+  "Return as a list of type/value pairs all the dynamic entries found in
+SEGMENT, the 'PT_DYNAMIC' segment of ELF.  In the result, each car is a DT_
+value, and the interpretation of the cdr depends on the type."
+  (define start
+    (elf-segment-offset segment))
+  (define bytes
+    (elf-bytes elf))
+  (define word-size
+    (elf-word-size elf))
+  (define byte-order
+    (elf-byte-order elf))
+  (define read-word
+    (word-reader word-size byte-order))
+
+  (let loop ((offset 0)
+             (result '()))
+    (if (>= offset (elf-segment-memsz segment))
+        (reverse result)
+        (let ((type  (read-word bytes (+ start offset)))
+              (value (read-word bytes (+ start offset word-size))))
+          (if (= type DT_NULL)                    ;finished?
+              (reverse result)
+              (loop (+ offset (* 2 word-size))
+                    (alist-cons type value result)))))))
+
+(define (vma->offset elf vma)
+  "Convert VMA, a virtual memory address, to an offset within ELF.
+
+Do that by looking at the loadable program segment (PT_LOAD) of ELF that
+contains VMA and by taking into account that segment's virtual address and
+offset."
+  ;; See 'offset_from_vma' in Binutils.
+  (define loads
+    (filter (lambda (segment)
+              (= (elf-segment-type segment) PT_LOAD))
+            (elf-segments elf)))
+
+  (let ((load (find (lambda (segment)
+                      (let ((vaddr (elf-segment-vaddr segment)))
+                        (and (>= vma vaddr)
+                             (< vma (+ (elf-segment-memsz segment)
+                                       vaddr)))))
+                    loads)))
+    (+ (- vma (elf-segment-vaddr load))
+       (elf-segment-offset load))))
+
+(define (dynamic-entries elf segment)
+  "Return all the dynamic entries found in SEGMENT, the 'PT_DYNAMIC' segment
+of ELF, as a list of type/value pairs.  The type is a DT_ value, and the value
+may be a string or an integer depending on the entry type (for instance, the
+value of DT_NEEDED entries is a string.)"
+  (define entries
+    (raw-dynamic-entries elf segment))
+
+  (define string-table-offset
+    (any (match-lambda
+            ((type . value)
+             (and (= type DT_STRTAB) value))
+            (_ #f))
+         entries))
+
+  (define (interpret-dynamic-entry type value)
+    (cond ((memv type (list DT_NEEDED DT_SONAME DT_RPATH DT_RUNPATH))
+           (if string-table-offset
+               (pointer->string
+                (bytevector->pointer (elf-bytes elf)
+                                     (vma->offset
+                                      elf
+                                      (+ string-table-offset value))))
+               value))
+          (else
+           value)))
+
+  (map (match-lambda
+         ((type . value)
+          (cons type (interpret-dynamic-entry type value))))
+       entries))
+
+
+;;;
+;;; High-level interface.
+;;;
+
+(define-record-type <elf-dynamic-info>
+  (%elf-dynamic-info soname needed rpath runpath)
+  elf-dynamic-info?
+  (soname    elf-dynamic-info-soname)
+  (needed    elf-dynamic-info-needed)
+  (rpath     elf-dynamic-info-rpath)
+  (runpath   elf-dynamic-info-runpath))
+
+(define search-path->list
+  (let ((not-colon (char-set-complement (char-set #\:))))
+    (lambda (str)
+      "Split STR on ':' characters."
+      (string-tokenize str not-colon))))
+
+(define (elf-dynamic-info elf)
+  "Return dynamic-link information for ELF as an <elf-dynamic-info> object, or
+#f if ELF lacks dynamic-link information."
+  (match (dynamic-link-segment elf)
+    (#f #f)
+    ((? elf-segment? dynamic)
+     (let ((entries (dynamic-entries elf dynamic)))
+       (%elf-dynamic-info (assv-ref entries DT_SONAME)
+                          (filter-map (match-lambda
+                                        ((type . value)
+                                         (and (= type DT_NEEDED) value))
+                                        (_ #f))
+                                      entries)
+                          (or (and=> (assv-ref entries DT_RPATH)
+                                     search-path->list)
+                              '())
+                          (or (and=> (assv-ref entries DT_RUNPATH)
+                                     search-path->list)
+                              '()))))))
+
+(define %libc-libraries
+  ;; List of libraries as of glibc 2.21 (there are more but those are
+  ;; typically mean to be LD_PRELOADed and thus do not appear as NEEDED.)
+  '("libanl.so"
+    "libcrypt.so"
+    "libc.so"
+    "libdl.so"
+    "libm.so"
+    "libpthread.so"
+    "libresolv.so"
+    "librt.so"
+    "libutil.so"))
+
+(define (libc-library? lib)
+  "Return #t if LIB is one of the libraries shipped with the GNU C Library."
+  (find (lambda (libc-lib)
+          (string-prefix? libc-lib lib))
+        %libc-libraries))
+
+(define* (validate-needed-in-runpath file
+                                     #:key (always-found? libc-library?))
+  "Return #t if all the libraries listed as FILE's 'DT_NEEDED' entries are
+present in its RUNPATH, or if FILE lacks dynamic-link information.  Return #f
+otherwise.  Libraries whose name matches ALWAYS-FOUND? are considered to be
+always available."
+  (let* ((elf     (call-with-input-file file
+                    (compose parse-elf get-bytevector-all)))
+         (dyninfo (elf-dynamic-info elf)))
+    (when dyninfo
+      (let* ((runpath   (elf-dynamic-info-runpath dyninfo))
+             (needed    (remove always-found?
+                                (elf-dynamic-info-needed dyninfo)))
+             (not-found (remove (cut search-path runpath <>)
+                                needed)))
+        (for-each (lambda (lib)
+                    (format (current-error-port)
+                            "error: '~a' depends on '~a', which cannot \
+be found in RUNPATH ~s~%"
+                            file lib runpath))
+                  not-found)
+        ;; (when (null? not-found)
+        ;;   (format (current-error-port) "~a is OK~%" file))
+        (null? not-found)))))
+
+;;; gremlin.scm ends here