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;;; GDB debugging support for Guile.
;;;
;;; Copyright 2014, 2015, 2017, 2020 Free Software Foundation, Inc.
;;;
;;; This program 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.
;;;
;;; This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
(define-module (guile-gdb)
#:use-module (system base types)
;; Note: (system vm debug) is 2.2-specific, but GDB might be built
;; with Guile 2.0.
#:autoload (system vm debug) (debug-context-from-image
debug-context-base
find-program-debug-info)
#:use-module ((gdb) #:hide (symbol? frame?))
#:use-module ((gdb) #:select ((symbol? . gdb:symbol?) (frame? . gdb:frame?)))
#:use-module (gdb printing)
#:use-module (srfi srfi-9)
#:use-module (srfi srfi-11)
#:use-module (srfi srfi-41)
#:use-module (ice-9 match)
#:use-module (ice-9 binary-ports)
#:export (%gdb-memory-backend
display-vm-frames))
;;; Commentary:
;;;
;;; This file defines GDB extensions to pretty-print 'SCM' objects, and
;;; to walk Guile's virtual machine stack.
;;;
;;; This file is installed under a name that follows the convention that
;;; allows GDB to auto-load it anytime the user is debugging libguile
;;; (info "(gdb) objfile-gdbdotext file").
;;;
;;; Code:
;; At run time, make sure we load (system base types) from the Guile
;; being debugged rather than from the Guile GDB is linked against.
(set! %load-path
(cons "/usr/share/guile/3.0" %load-path))
(set! %load-compiled-path
(cons "/usr/lib/guile/3.0/site-ccache" %load-compiled-path))
(reload-module (resolve-module '(system base types)))
(define (type-name-from-descriptor descriptor-array type-number)
"Return the name of the type TYPE-NUMBER as seen in DESCRIPTOR-ARRAY, or #f
if the information is not available."
(let ((descriptors (lookup-global-symbol descriptor-array)))
(and descriptors
(let ((code (type-code (symbol-type descriptors))))
(or (= TYPE_CODE_ARRAY code)
(= TYPE_CODE_PTR code)))
(let* ((type-descr (value-subscript (symbol-value descriptors)
type-number))
(name (value-field type-descr "name")))
(value->string name)))))
(define %gdb-memory-backend
;; The GDB back-end to access the inferior's memory.
;; When run through 'rr replay', even the 'void' type is initially
;; unavailable. Thus, delay lookup until it's actually needed.
(let ((void* (delay (type-pointer (lookup-type "void")))))
(define (dereference-word address)
;; Return the word at ADDRESS.
(value->integer
(value-dereference (value-cast (make-value address)
(type-pointer (force void*))))))
(define (open address size)
;; Return a port to the SIZE bytes starting at ADDRESS.
(if size
(open-memory #:start address #:size size)
(open-memory #:start address)))
(define (type-name kind number)
;; Return the type name of KIND type NUMBER.
(type-name-from-descriptor (case kind
((smob) "scm_smobs")
((port) "scm_ptobs"))
number))
(memory-backend dereference-word open type-name)))
;;;
;;; GDB pretty-printer registration.
;;;
(define scm-value->string
(lambda* (value #:optional (backend %gdb-memory-backend))
"Return a representation of value VALUE as a string."
(object->string (scm->object (value->integer value) backend))))
(define (make-scm-pretty-printer-worker obj)
(define (list->iterator list)
(make-iterator list list
(let ((n 0))
(lambda (iter)
(match (iterator-progress iter)
(() (end-of-iteration))
((elt . list)
(set-iterator-progress! iter list)
(let ((name (format #f "[~a]" n)))
(set! n (1+ n))
(cons name (object->string elt)))))))))
(cond
((string? obj)
(make-pretty-printer-worker
"string" ; display hint
(lambda (printer) obj)
#f))
((and (array? obj)
(match (array-shape obj)
(((0 _)) #t)
(_ #f)))
(make-pretty-printer-worker
"array" ; display hint
(lambda (printer)
(let ((tag (array-type obj)))
(case tag
((#t) "#<vector>")
((b) "#<bitvector>")
(else (format #f "#<~avector>" tag)))))
(lambda (printer)
(list->iterator (array->list obj)))))
((inferior-struct? obj)
(make-pretty-printer-worker
"array" ; display hint
(lambda (printer)
(format #f "#<struct ~a>" (inferior-struct-name obj)))
(lambda (printer)
(list->iterator (inferior-struct-fields obj)))))
(else
(make-pretty-printer-worker
#f ; display hint
(lambda (printer)
(object->string obj))
#f))))
(define %scm-pretty-printer
(make-pretty-printer
"SCM"
(lambda (pp value)
(let ((name (type-name (value-type value))))
(and (and name (string=? name "SCM"))
(make-scm-pretty-printer-worker
(scm->object (value->integer value) %gdb-memory-backend)))))))
(define* (register-pretty-printer #:optional objfile)
(prepend-pretty-printer! objfile %scm-pretty-printer))
(register-pretty-printer)
;;;
;;; VM stack walking.
;;;
(define-record-type <vm-frame>
(make-vm-frame ip sp fp saved-ip saved-fp)
vm-frame?
(ip vm-frame-ip)
(sp vm-frame-sp)
(fp vm-frame-fp)
(saved-ip vm-frame-saved-ip)
(saved-fp vm-frame-saved-fp))
;; See libguile/frames.h.
(define* (vm-frame ip sp fp #:optional (backend %gdb-memory-backend))
"Return the components of the stack frame at FP."
(define ip-type (type-pointer (lookup-type "uint32_t")))
(define uint-type (type-pointer (lookup-type "uintptr_t")))
(make-vm-frame ip
sp
fp
;; fp[0] is the return address.
(value-dereference (value-cast fp (type-pointer ip-type)))
;; fp[1] is the offset to the previous frame pointer.
(value-add fp
(value->integer
(value-dereference
(value-cast (value-add fp 1)
(type-pointer uint-type)))))))
(define (vm-engine-frame? frame)
(let ((sym (frame-function frame)))
(and sym
(member (symbol-name sym)
'("vm_debug_engine" "vm_regular_engine")))))
(define (find-vp)
"Find the scm_vm pointer for the current thread."
(match (lookup-symbol "scm_i_current_thread")
((#f _)
#f)
((symbol _)
(let ((thread (symbol-value symbol)))
(value-field thread "vm")))))
(define (newest-vm-frame)
"Return the newest VM frame or #f."
(let ((vp (find-vp)))
(and vp
(vm-frame (value-field vp "ip")
(value-field vp "sp")
(value-field vp "fp")))))
(define* (vm-frame-older frame #:optional (backend %gdb-memory-backend))
(let ((ip (vm-frame-saved-ip frame))
(sp (value-sub (vm-frame-fp frame) 3))
(fp (vm-frame-saved-fp frame)))
(and (not (zero? (value->integer ip)))
(vm-frame ip sp fp backend))))
(define (vm-frames)
"Return a SRFI-41 stream of the current VM frame stack."
(stream-unfold identity
vm-frame?
vm-frame-older
(newest-vm-frame)))
(define (vm-frame-locals frame)
(let ((fp (vm-frame-fp frame))
(sp (vm-frame-sp frame)))
(let lp ((slot 0) (ptr fp))
(if (value<=? ptr sp)
(acons (string-append "v" (number->string slot))
(value-dereference ptr)
(lp (1+ slot) (value-add ptr 1)))
'()))))
(define (lookup-symbol-or-false name)
(match (lookup-symbol name)
(#f #f)
((sym _) sym)))
(define (find-mapped-elf-image addr)
(let ((array (lookup-symbol-or-false "mapped_elf_images"))
(count (lookup-symbol-or-false "mapped_elf_images_count")))
(and array count
(let ((array (symbol-value array))
(count (value->integer (symbol-value count))))
(let lp ((start 0) (end count))
(if (< start end)
(let ((n (+ start (ash (- end start) -1))))
(if (value<? addr (value-field (value-add array n) "end"))
(lp start n)
(lp (1+ n) end)))
(let ((mei (value-add array start)))
(and (value<=? (value-field mei "start") addr)
mei))))))))
(define (vm-frame-program-debug-info frame)
(let ((addr (vm-frame-ip frame)))
(and=> (find-mapped-elf-image addr)
(lambda (mei)
(let* ((start (value->integer (value-field mei "start")))
(size (- (value->integer (value-field mei "end"))
start))
(mem-port (open-memory #:start start #:size size))
(bv (get-bytevector-all mem-port))
(ctx (debug-context-from-image bv)))
;; The image is in this process at "bv", but in the
;; inferior at mei.start. Therefore we relocate addr
;; before we look for the PDI.
(let ((addr (+ (value->integer addr)
(- (debug-context-base ctx) start))))
(find-program-debug-info addr ctx)))))))
(define (vm-frame-function-name frame)
(define (default-name)
"[unknown]")
(cond
((false-if-exception (vm-frame-program-debug-info frame))
=> (lambda (pdi)
(or (and=> (program-debug-info-name pdi) symbol->string)
"[anonymous]")))
(else
(let ((ip (vm-frame-ip frame)))
(define (ip-in-symbol? name)
(let ((sym (lookup-symbol-or-false name)))
(and sym
(not (value-optimized-out? (symbol-value sym)))
(let* ((val (symbol-value sym))
(size (type-sizeof (value-type val)))
(char* (type-pointer (arch-char-type (current-arch))))
(val-as-char* (value-cast val char*)))
(and (value<=? val-as-char* ip)
(value<? ip (value-add val-as-char* size)))))))
(cond
((ip-in-symbol? "vm_boot_continuation_code") "[boot continuation]")
;; FIXME: For subrs, read the name from slot 0 in the frame.
((ip-in-symbol? "subr_stub_code") "[subr call]")
((ip-in-symbol? "vm_builtin_apply_code") "apply")
((ip-in-symbol? "vm_builtin_values_code") "values")
((ip-in-symbol? "vm_builtin_abort_to_prompt_code") "abort-to-prompt")
((ip-in-symbol? "vm_builtin_call_with_values_code") "call-with-values")
((ip-in-symbol? "vm_builtin_call_with_current_continuation_code")
"call-with-current-continuation")
((ip-in-symbol? "continuation_stub_code") "[continuation]")
((ip-in-symbol? "compose_continuation_code") "[delimited continuation]")
((ip-in-symbol? "foreign_stub_code") "[ffi call]")
(else (default-name)))))))
(define (vm-frame-source frame)
(let* ((ip (value->integer (vm-frame-ip frame)))
(pdi (vm-frame-program-debug-info frame)))
(and pdi
(find-source-for-addr (program-debug-info-addr pdi)
(program-debug-info-context pdi)))))
(define* (dump-vm-frame frame #:optional (port (current-output-port)))
(format port " name: ~a~%" (vm-frame-function-name frame))
(format port " ip: 0x~x~%" (value->integer (vm-frame-ip frame)))
(format port " fp: 0x~x~%" (value->integer (vm-frame-fp frame)))
(for-each (match-lambda
((name . val)
(let ((obj (scm->object (value->integer val) %gdb-memory-backend)))
(format port " ~a: ~a~%" name obj))))
(vm-frame-locals frame)))
(define* (display-vm-frames #:optional (port (current-output-port)))
"Display the VM frames on PORT."
(stream-for-each (lambda (frame)
(dump-vm-frame frame port))
(vm-frames)))
(register-command!
(make-command "guile-backtrace"
#:command-class COMMAND_STACK
#:doc "Display a backtrace of Guile's VM stack for the \
current thread"
#:invoke (lambda (self args from-tty)
(display-vm-frames))))
;;;
;;; Frame filters.
;;;
(define-syntax compile-time-cond
(lambda (x)
(syntax-case x ()
((_ (test body ...) clause ...)
(if (eval (syntax->datum #'test) (current-module))
#'(begin body ...)
#'(compile-time-cond clause ...)))
((_)
#'(begin)))))
(compile-time-cond
;; What follows depends on (gdb frame-filters), which unfortunately has
;; not yet been merged in GDB:
;; <https://sourceware.org/ml/gdb-patches/2015-02/msg00362.html>.
((false-if-exception (resolve-interface '(gdb frame-filters)))
(use-modules (gdb frame-filters))
(define (snarfy-frame-decorator dec)
(let* ((frame (decorated-frame-frame dec))
(sym (frame-function frame)))
(or
(and sym
(gdb:symbol? sym)
(let ((c-name (symbol-name sym)))
(match (lookup-symbol (string-append "s_" c-name))
(#f #f)
((scheme-name-sym _)
(and (string-prefix?
"const char ["
(type-print-name (symbol-type scheme-name-sym)))
(let* ((scheme-name-value (symbol-value scheme-name-sym))
(scheme-name (value->string scheme-name-value))
(name (format #f "~a [~a]" scheme-name c-name)))
(redecorate-frame dec #:function-name name)))))))
dec)))
(define* (vm-frame-filter gdb-frames #:optional (vm-frames (vm-frames)))
(define (synthesize-frame gdb-frame vm-frame)
(let* ((ip (value->integer (vm-frame-ip vm-frame)))
(source (vm-frame-source vm-frame)))
(redecorate-frame gdb-frame
#:function-name (vm-frame-function-name vm-frame)
#:address ip
#:filename (and=> source source-file)
#:line (and=> source source-line-for-user)
#:arguments '()
#:locals (vm-frame-locals vm-frame)
#:children '())))
(define (recur gdb-frame gdb-frames vm-frames)
(stream-cons gdb-frame
(vm-frame-filter gdb-frames vm-frames)))
(cond
((or (stream-null? gdb-frames)
(not (lookup-symbol "vm_boot_continuation_code")))
gdb-frames)
(else
(let ((gdb-frame (stream-car gdb-frames))
(gdb-frames (stream-cdr gdb-frames)))
(match (lookup-symbol "vm_boot_continuation_code")
((boot-sym _)
(let ((boot-ptr (symbol-value boot-sym)))
(cond
((vm-engine-frame? (decorated-frame-frame gdb-frame))
(let lp ((children (reverse
(decorated-frame-children gdb-frame)))
(vm-frames vm-frames))
(define (finish reversed-children vm-frames)
(let ((children (reverse reversed-children)))
(recur (redecorate-frame gdb-frame #:children children)
gdb-frames
vm-frames)))
(cond
((stream-null? vm-frames)
(finish children vm-frames))
(else
(let* ((vm-frame (stream-car vm-frames))
(vm-frames (stream-cdr vm-frames)))
(if (value=? (vm-frame-ip vm-frame) boot-ptr)
;; Drop the boot frame and finish.
(finish children vm-frames)
(lp (cons (synthesize-frame gdb-frame vm-frame)
children)
vm-frames)))))))
(else
(recur gdb-frame gdb-frames vm-frames))))))))))
(add-frame-filter!
(make-decorating-frame-filter "guile-snarf-decorator"
snarfy-frame-decorator
#:objfile (current-objfile)))
(add-frame-filter!
(make-frame-filter "guile-vm-frame-filter"
vm-frame-filter
#:objfile (current-objfile))))
(#t #f))
;;; libguile-2.2-gdb.scm ends here