From ef52b3992c95be4a891dc147990145e3656b0e62 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Tue, 17 Feb 2015 11:00:21 +0100
Subject: [PATCH] De-bitrot libguile-2.2-gdb.scm

* libguile/libguile-2.2-gdb.scm: Update to work with Guile 2.2 stacks.
  Represent the VM stack as a SRFI-41 stream, which will work better
  with the frame filter interface.  Add support for getting the vm
  frame's function name, if possible.
---
 libguile/libguile-2.2-gdb.scm | 205 +++++++++++++++++++++++++---------
 1 file changed, 155 insertions(+), 50 deletions(-)

diff --git a/libguile/libguile-2.2-gdb.scm b/libguile/libguile-2.2-gdb.scm
index 93ba1a3ea..3a8af0d9b 100644
--- a/libguile/libguile-2.2-gdb.scm
+++ b/libguile/libguile-2.2-gdb.scm
@@ -1,6 +1,6 @@
 ;;; GDB debugging support for Guile.
 ;;;
-;;; Copyright 2014 Free Software Foundation, Inc.
+;;; Copyright 2014, 2015 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
@@ -17,9 +17,15 @@
 
 (define-module (guile-gdb)
   #:use-module (system base types)
-  #:use-module ((gdb) #:hide (symbol?))
+  #:use-module (system vm debug)
+  #: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))
 
@@ -102,63 +108,162 @@ if the information is not available."
 ;;; VM stack walking.
 ;;;
 
-(define (find-vm-engine-frame)
-  "Return the bottom-most frame containing a call to the VM engine."
-  (define (vm-engine-frame? frame)
-    (let ((sym (frame-function frame)))
-      (and sym
-           (member (symbol-name sym)
-                   '("vm_debug_engine" "vm_regular_engine")))))
+(define ip-type (type-pointer (lookup-type "scm_t_uint32")))
+(define fp-type (type-pointer (lookup-type "SCM")))
+(define sp-type (type-pointer (lookup-type "SCM")))
 
+(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."
+  (make-vm-frame ip
+                 sp
+                 fp
+                 (value-dereference (value-cast (value-sub fp 1)
+                                                (type-pointer ip-type)))
+                 (value-dereference (value-cast (value-sub fp 2)
+                                                (type-pointer fp-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."
   (let loop ((frame (newest-frame)))
     (and frame
          (if (vm-engine-frame? frame)
-             frame
+             (frame-read-var frame "vp")
              (loop (frame-older frame))))))
 
-(define (vm-stack-pointer)
-  "Return the current value of the VM stack pointer or #f."
-  (let ((frame (find-vm-engine-frame)))
-    (and frame
-         (frame-read-var frame "sp"))))
+(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-pointer)
-  "Return the current value of the VM frame pointer or #f."
-  (let ((frame (find-vm-engine-frame)))
-    (and frame
-         (frame-read-var frame "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 fp)))
+         (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)
+    (format #f "0x~x" (value->integer (vm-frame-ip frame))))
+  (cond
+   ((vm-frame-program-debug-info frame)
+    => (lambda (pdi)
+         (or (and=> (program-debug-info-name pdi) symbol->string)
+             (default-name))))
+   (else
+    (let ((ip (vm-frame-ip frame)))
+      (define (ip-in-symbol? name)
+        (let ((sym (lookup-symbol-or-false name)))
+          (and 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* (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."
-  (define (display-objects start end)
-    ;; Display all the objects (arguments and local variables) located
-    ;; between START and END.
-    (let loop ((number  0)
-               (address start))
-      (when (and (> start 0) (<= address end))
-        (let ((object (dereference-word %gdb-memory-backend address)))
-          ;; TODO: Push onto GDB's value history.
-          (format port "  slot ~a -> ~s~%"
-                  number (scm->object object %gdb-memory-backend)))
-        (loop (+ 1 number) (+ address %word-size)))))
-
-  (let loop ((number 0)
-             (sp     (value->integer (vm-stack-pointer)))
-             (fp     (value->integer (vm-frame-pointer))))
-    (unless (zero? fp)
-      (let-values (((ra mvra link proc)
-                    (vm-frame fp %gdb-memory-backend)))
-        (format port "#~a ~s~%" number (scm->object proc %gdb-memory-backend))
-        (display-objects fp sp)
-        (loop (+ 1 number) (- fp (* 5 %word-size)) link)))))
-
-;; See libguile/frames.h.
-(define* (vm-frame fp #:optional (backend %gdb-memory-backend))
-  "Return the components of the stack frame at FP."
-  (let ((caller (dereference-word backend (- fp %word-size)))
-        (ra     (dereference-word backend (- fp (* 2 %word-size))))
-        (mvra   (dereference-word backend (- fp (* 3 %word-size))))
-        (link   (dereference-word backend (- fp (* 4 %word-size)))))
-    (values ra mvra link caller)))
+  (stream-for-each (lambda (frame)
+                     (dump-vm-frame frame port))
+                   (vm-frames)))
 
 ;;; libguile-2.2-gdb.scm ends here
-- 
2.20.1