;;; GNU Guix --- Functional package management for GNU ;;; Copyright © 2018, 2023 Ludovic Courtès ;;; ;;; 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 . (define-module (guix build debug-link) #:use-module (guix elf) #:use-module ((guix build utils) #:select (find-files elf-file? make-file-writable)) #:use-module (rnrs bytevectors) #:use-module (rnrs io ports) #:use-module (srfi srfi-1) #:use-module (system foreign) #:use-module (ice-9 match) #:export (debuglink-crc32 elf-debuglink set-debuglink-crc graft-debug-links)) ;;; Commentary: ;;; ;;; This module provides tools to deal with '.gnu_debuglink' sections in ELF ;;; files. These sections are created by 'objcopy --add-gnu-debuglink' to ;;; create separate debug files (info "(gdb) Separate Debug Files"). ;;; ;;; The main facility of this module is 'graft-debug-links', which allows us ;;; to update the cyclic redundancy check (CRC) that appears in ;;; '.gnu_debuglink' sections when grafting, such that separate debug files ;;; remain usable after grafting. Failing to do that, GDB would complain ;;; about CRC mismatch---see . ;;; ;;; Code: (define %crc32-table ;; CRC table taken from "(gdb) Separate Debug Files". ;; TODO: Wouldn't it be nice to generate it "from source" with a macro? #(#x00000000 #x77073096 #xee0e612c #x990951ba #x076dc419 #x706af48f #xe963a535 #x9e6495a3 #x0edb8832 #x79dcb8a4 #xe0d5e91e #x97d2d988 #x09b64c2b #x7eb17cbd #xe7b82d07 #x90bf1d91 #x1db71064 #x6ab020f2 #xf3b97148 #x84be41de #x1adad47d #x6ddde4eb #xf4d4b551 #x83d385c7 #x136c9856 #x646ba8c0 #xfd62f97a #x8a65c9ec #x14015c4f #x63066cd9 #xfa0f3d63 #x8d080df5 #x3b6e20c8 #x4c69105e #xd56041e4 #xa2677172 #x3c03e4d1 #x4b04d447 #xd20d85fd #xa50ab56b #x35b5a8fa #x42b2986c #xdbbbc9d6 #xacbcf940 #x32d86ce3 #x45df5c75 #xdcd60dcf #xabd13d59 #x26d930ac #x51de003a #xc8d75180 #xbfd06116 #x21b4f4b5 #x56b3c423 #xcfba9599 #xb8bda50f #x2802b89e #x5f058808 #xc60cd9b2 #xb10be924 #x2f6f7c87 #x58684c11 #xc1611dab #xb6662d3d #x76dc4190 #x01db7106 #x98d220bc #xefd5102a #x71b18589 #x06b6b51f #x9fbfe4a5 #xe8b8d433 #x7807c9a2 #x0f00f934 #x9609a88e #xe10e9818 #x7f6a0dbb #x086d3d2d #x91646c97 #xe6635c01 #x6b6b51f4 #x1c6c6162 #x856530d8 #xf262004e #x6c0695ed #x1b01a57b #x8208f4c1 #xf50fc457 #x65b0d9c6 #x12b7e950 #x8bbeb8ea #xfcb9887c #x62dd1ddf #x15da2d49 #x8cd37cf3 #xfbd44c65 #x4db26158 #x3ab551ce #xa3bc0074 #xd4bb30e2 #x4adfa541 #x3dd895d7 #xa4d1c46d #xd3d6f4fb #x4369e96a #x346ed9fc #xad678846 #xda60b8d0 #x44042d73 #x33031de5 #xaa0a4c5f #xdd0d7cc9 #x5005713c #x270241aa #xbe0b1010 #xc90c2086 #x5768b525 #x206f85b3 #xb966d409 #xce61e49f #x5edef90e #x29d9c998 #xb0d09822 #xc7d7a8b4 #x59b33d17 #x2eb40d81 #xb7bd5c3b #xc0ba6cad #xedb88320 #x9abfb3b6 #x03b6e20c #x74b1d29a #xead54739 #x9dd277af #x04db2615 #x73dc1683 #xe3630b12 #x94643b84 #x0d6d6a3e #x7a6a5aa8 #xe40ecf0b #x9309ff9d #x0a00ae27 #x7d079eb1 #xf00f9344 #x8708a3d2 #x1e01f268 #x6906c2fe #xf762575d #x806567cb #x196c3671 #x6e6b06e7 #xfed41b76 #x89d32be0 #x10da7a5a #x67dd4acc #xf9b9df6f #x8ebeeff9 #x17b7be43 #x60b08ed5 #xd6d6a3e8 #xa1d1937e #x38d8c2c4 #x4fdff252 #xd1bb67f1 #xa6bc5767 #x3fb506dd #x48b2364b #xd80d2bda #xaf0a1b4c #x36034af6 #x41047a60 #xdf60efc3 #xa867df55 #x316e8eef #x4669be79 #xcb61b38c #xbc66831a #x256fd2a0 #x5268e236 #xcc0c7795 #xbb0b4703 #x220216b9 #x5505262f #xc5ba3bbe #xb2bd0b28 #x2bb45a92 #x5cb36a04 #xc2d7ffa7 #xb5d0cf31 #x2cd99e8b #x5bdeae1d #x9b64c2b0 #xec63f226 #x756aa39c #x026d930a #x9c0906a9 #xeb0e363f #x72076785 #x05005713 #x95bf4a82 #xe2b87a14 #x7bb12bae #x0cb61b38 #x92d28e9b #xe5d5be0d #x7cdcefb7 #x0bdbdf21 #x86d3d2d4 #xf1d4e242 #x68ddb3f8 #x1fda836e #x81be16cd #xf6b9265b #x6fb077e1 #x18b74777 #x88085ae6 #xff0f6a70 #x66063bca #x11010b5c #x8f659eff #xf862ae69 #x616bffd3 #x166ccf45 #xa00ae278 #xd70dd2ee #x4e048354 #x3903b3c2 #xa7672661 #xd06016f7 #x4969474d #x3e6e77db #xaed16a4a #xd9d65adc #x40df0b66 #x37d83bf0 #xa9bcae53 #xdebb9ec5 #x47b2cf7f #x30b5ffe9 #xbdbdf21c #xcabac28a #x53b39330 #x24b4a3a6 #xbad03605 #xcdd70693 #x54de5729 #x23d967bf #xb3667a2e #xc4614ab8 #x5d681b02 #x2a6f2b94 #xb40bbe37 #xc30c8ea1 #x5a05df1b #x2d02ef8d)) (define (debuglink-crc32 port) "Compute the 32-bit CRC used in in '.gnu_debuglink' over the data read from PORT and return it." ;(info "(gdb) Separate Debug Files") (let loop ((crc #xffffffff)) (let ((byte (get-u8 port))) (if (eof-object? byte) (logand (lognot crc) #xffffffff) (let* ((index (logand (logxor crc byte) #xff)) (lhs (vector-ref %crc32-table index))) (loop (logxor lhs (ash crc -8)))))))) (define (section-contents elf section) ;XXX: copied from linux-modules.scm "Return the contents of SECTION in ELF as a bytevector." (let* ((contents (make-bytevector (elf-section-size section)))) (bytevector-copy! (elf-bytes elf) (elf-section-offset section) contents 0 (elf-section-size section)) contents)) (define null-terminated-bytevector->string (compose pointer->string bytevector->pointer)) (define (elf-debuglink elf) "Return two values: the '.gnu_debuglink' file name of ELF and its CRC. Return #f for both if ELF lacks a '.gnu_debuglink' section." (let ((section (elf-section-by-name elf ".gnu_debuglink"))) (if section (let ((size (elf-section-size section)) (bv (section-contents elf section)) (endianness (elf-byte-order elf))) (values (null-terminated-bytevector->string bv) (bytevector-u32-ref bv (- size 4) endianness))) (values #f #f)))) (define (elf-debuglink-crc-offset elf) "Return the offset of the '.gnu_debuglink' 32-bit CRC, or #f if ELF lacks a '.gnu_debuglink' section." (let ((section (elf-section-by-name elf ".gnu_debuglink"))) (and section (+ (elf-section-offset section) (elf-section-size section) -4)))) (define (set-debuglink-crc file debug-file) "Compute the CRC of DEBUG-FILE and set it as the '.gnu_debuglink' CRC in FILE." (let* ((elf (parse-elf (call-with-input-file file get-bytevector-all))) (offset (elf-debuglink-crc-offset elf))) (and offset (let* ((crc (call-with-input-file debug-file debuglink-crc32)) (bv (make-bytevector 4))) (bytevector-u32-set! bv 0 crc (elf-byte-order elf)) (let ((port (open file O_RDWR))) (set-port-position! port offset) (put-bytevector port bv) (close-port port)))))) ;;; ;;; Updating debuglink CRC. ;;; (define (find-elf-files outputs) "Return the list of ELF files found in OUTPUTS, a list of top-level store directories." (define directories (append-map (lambda (output) (list (string-append output "/bin") (string-append output "/sbin") (string-append output "/lib") (string-append output "/libexec"))) outputs)) (append-map (lambda (directory) (filter (lambda (file) (catch 'system-error (lambda () (elf-file? file)) (lambda args ;; FILE might be a dangling symlink. (if (= ENOENT (system-error-errno args)) #f (apply throw args))))) (with-error-to-port (%make-void-port "w") (lambda () (find-files directory))))) directories)) (define* (graft-debug-links old-outputs new-outputs mapping #:key (log-port (current-error-port))) "Update the '.gnu_debuglink' CRCs found in ELF files of NEW-OUTPUTS, provided NEW-OUTPUTS contains a \"debug\" output, such that those CRCs match those of the corresponding '.debug' files found in the \"debug\" output. This procedure is meant to be used as a \"grafting hook\" by (guix build graft)." (match (assoc-ref new-outputs "debug") (#f #t) ;nothing to do (debug-directory (let ((files (find-elf-files (filter-map (match-lambda (("debug" . _) #f) ((name . directory) directory)) new-outputs)))) (for-each (lambda (file) (let ((debug (string-append debug-directory "/lib/debug" file ".debug"))) (when (file-exists? debug) (format log-port "updating '.gnu_debuglink' CRC in '~a'~%" file) (make-file-writable file) (set-debuglink-crc file debug)))) files)))))