;;; Guile runtime debug information ;;; Copyright (C) 2013 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 library; if not, write to the Free Software ;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA ;;; Commentary: ;;; ;;; Guile's RTL compiler and linker serialize debugging information into ;;; separate sections of the ELF image. This module reads those ;;; sections. ;;; ;;; Code: (define-module (system vm debug) #:use-module (system vm elf) #:use-module (system vm objcode) #:use-module (system foreign) #:use-module (rnrs bytevectors) #:use-module (ice-9 match) #:use-module (srfi srfi-9) #:export (debug-context-image program-debug-info-name program-debug-info-context program-debug-info-image program-debug-info-offset program-debug-info-addr program-debug-info-u32-offset program-debug-info-u32-offset-end find-debug-context find-program-debug-info)) ;;; A compiled procedure comes from a specific loaded ELF image. A ;;; debug context identifies that image. ;;; (define-record-type (make-debug-context elf base text-base) debug-context? (elf debug-context-elf) ;; Address at which this image is loaded in memory, in bytes. (base debug-context-base) ;; Offset of the text section relative to the image start, in bytes. (text-base debug-context-text-base)) (define (debug-context-image context) "Return the bytevector aliasing the mapped ELF image corresponding to @var{context}." (elf-bytes (debug-context-elf context))) ;;; A program debug info (PDI) is a handle on debugging meta-data for a ;;; particular program. ;;; (define-record-type (make-program-debug-info context name offset size) program-debug-info? (context program-debug-info-context) (name program-debug-info-name) ;; Offset of the procedure in the text section, in bytes. (offset program-debug-info-offset) (size program-debug-info-size)) (define (program-debug-info-addr pdi) "Return the address in memory of the entry of the program represented by the debugging info @var{pdi}." (+ (program-debug-info-offset pdi) (debug-context-text-base (program-debug-info-context pdi)) (debug-context-base (program-debug-info-context pdi)))) (define (program-debug-info-image pdi) "Return the ELF image containing @var{pdi}, as a bytevector." (debug-context-image (program-debug-info-context pdi))) (define (program-debug-info-u32-offset pdi) "Return the start address of the program represented by @var{pdi}, as an offset from the beginning of the ELF image in 32-bit units." (/ (+ (program-debug-info-offset pdi) (debug-context-text-base (program-debug-info-context pdi))) 4)) (define (program-debug-info-u32-offset-end pdi) "Return the end address of the program represented by @var{pdi}, as an offset from the beginning of the ELF image in 32-bit units." (/ (+ (program-debug-info-size pdi) (program-debug-info-offset pdi) (debug-context-text-base (program-debug-info-context pdi))) 4)) (define (find-debug-context addr) "Find and return the debugging context corresponding to the ELF image containing the address @var{addr}. @var{addr} is an integer." (let* ((bv (find-mapped-elf-image addr)) (elf (parse-elf bv)) (base (pointer-address (bytevector->pointer (elf-bytes elf)))) (text-base (elf-section-offset (or (elf-section-by-name elf ".rtl-text") (error "ELF object has no text section"))))) (make-debug-context elf base text-base))) (define (find-elf-symbol elf text-offset) "Search the symbol table of @var{elf} for the ELF symbol containing @var{text-offset}. @var{text-offset} is a byte offset in the text section of the ELF image. Returns an ELF symbol, or @code{#f}." (and=> (elf-section-by-name elf ".symtab") (lambda (symtab) (let ((len (elf-symbol-table-len symtab)) (strtab (elf-section elf (elf-section-link symtab)))) ;; The symbols should be sorted, but maybe somehow that fails ;; (for example if multiple objects are relinked together). So, ;; a modicum of tolerance. (define (bisect) ;; FIXME: Implement. #f) (define (linear-search) (let lp ((n 0)) (and (< n len) (let ((sym (elf-symbol-table-ref elf symtab n strtab))) (if (and (<= (elf-symbol-value sym) text-offset) (< text-offset (+ (elf-symbol-value sym) (elf-symbol-size sym)))) sym (lp (1+ n))))))) (or (bisect) (linear-search)))))) (define* (find-program-debug-info addr #:optional (context (find-debug-context addr))) "Find and return the @code{} containing @var{addr}, or @code{#f}." (cond ((find-elf-symbol (debug-context-elf context) (- addr (debug-context-base context) (debug-context-text-base context))) => (lambda (sym) (make-program-debug-info context (and=> (elf-symbol-name sym) ;; The name might be #f if ;; the string table was ;; stripped somehow. (lambda (x) (and (string? x) (not (string-null? x)) (string->symbol x)))) (elf-symbol-value sym) (elf-symbol-size sym)))) (else #f)))