1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406
|
; Part of Scheme 48 1.9. See file COPYING for notices and license.
; Authors: Richard Kelsey, Jonathan Rees, David Frese, Mike Sperber, Norbert Freudemann
; Steps:
; 1. Trace everything reachable from RESUME-PROC and from the exported
; bindings (which we must assume are reachable because we cannot trace
; from the imported bindigns via external data structures to the
; exported bindings). All reachable objects are assigned addresses in
; the image and put in a list in the order they will appear in the image.
; 2. Write the ASCII image header.
; 3. Traverse the list of reachable objects writing them out into the
; image file.
; 4. Write out the symbol, imported binding, and exported binding tables,
; updating the buckets to only include those values which were traced.
; 5. Write out a vector containing all records with resume methods.
;
; Several types of objects do not get copied as-is:
; - Weak pointers
; The value is written as #F if it is not in the image.
; - Symbols, shared-bindings
; The next fields, which link the buckets in the hash tables holding
; these, are written out so as to elide any bucket entries that were
; not found during tracing. Imported bindings have their values
; written as unassigned.
; - Channels
; Written out as closed.
; - Undumpable records
; These are treated as if they were the value in the record's first slot.
;
; We can run out of memory. When this happens we disable the hash table
; to keep from trying to make further progress. We can also get i/o errors,
; but these are mostly taken care by the image-writing utilities.
(define (s48-write-image resume-proc undumpables port)
(begin-making-image undumpables)
(if (image-write-init port)
(let ((resume-proc (trace-image-value resume-proc)))
(trace-exported-bindings (s48-exported-bindings))
(make-image)
(cond ((table-okay? *stob-table*)
(write-header *resumer-records* resume-proc image-descriptor port)
(write-descriptor false) ; for endianess check
(write-image)
(empty-image-buffer!)
(deallocate-areas)
(deallocate-table *stob-table*)
(image-write-terminate)
(image-write-status))
(else
(deallocate-table *stob-table*)
(image-write-terminate)
(enum errors out-of-memory))))
(enum errors out-of-memory)))
; The interface to the GC consists of the following, listed in the order in
; which they are called.
;
; (BEGIN-MAKING-IMAGE start-address undumpable) ; UNDUMPABLE is a vector
;
; (TRACE-IMAGE-VALUE value) -> value in image ; identifies roots
;
; (MAKE-IMAGE) ; scan
; Scan everything, then make the symbol and imported/exported tables.
; Walk the stob table to count the resumer records and create that table
; as well.
;
; (IMAGE-SIZE)
; (IMAGE-SYMBOL-TABLE) -> stob in image
; (IMAGE-EXPORTED-BINDINGS) -> stob in image
; (IMAGE-IMPORTED-BINDINGS) -> stob in image
; (RESUMER-RECORDS) -> stob in image
; To find the resumer records we walk the table looking for them.
; First to find out how many and then a second time when we write
; the vector out.
;
; (WRITE-IMAGE) ; must come last
; Write out all the objects in the stob table and then the symbol and
; imported/exported tables and finally the resumer records.
(define (begin-making-image undumpable)
(set! *stob-table* (make-table))
(set! *first-stob* false)
(set! *last-stob* (null-pointer))
(set! *undumpable-records* undumpable)
(set! *undumpable-count* 0)
(set! *resumer-count* 0)
(begin-making-image/gc-specific))
(define *stob-table*) ; Table mapping stobs to image-location records.
(define *first-stob*) ; The beginning and end of the list
(define *last-stob*) ; of image-location records.
(define *resumer-count*) ; Number of resumer records found so far.
(define *resumer-records*) ; Vector of resumer records created in image.
(define *undumpable-records*) ; Vector passed to us for undumpable records.
(define *undumpable-count*) ; How many we have found so far.
; Is THING in the image.
(define (image-extant? thing)
(not (and (stob? thing)
(null-pointer? (table-ref *stob-table* thing)))))
; Add THING to the image if it is not already there. Returns the value of
; THING in the image. If there has been an error in table we proceed without
; doing anything.
(define (trace-image-value thing)
(if (stob? thing)
(let ((have (table-ref *stob-table* thing)))
(cond ((not (null-pointer? have))
(image-location-new-descriptor have))
((undumpable? thing)
(trace-undumpable thing))
(else
(add-new-image-object thing))))
thing))
; Note that we have seen THING and then trace its alias. We add an entry to
; the table so that THING will not be traced again and so that references to
; it will be written out as the alias.
(define (trace-undumpable thing)
(note-undumpable! thing)
(let* ((alias (undumpable-alias thing))
(new-alias (trace-image-value alias))
(new (make-image-location new-alias)))
(if (null-pointer? new)
(break-table! *stob-table*)
(table-set! *stob-table* thing new))
new-alias))
; Allocate space for STOB in the image and create a new-descriptor record
; for it.
(define (add-new-image-object stob)
(receive (new-descriptor new)
(allocate-new-image-object stob)
(if (null-pointer? new)
(break-table! *stob-table*)
(begin
(if (false? *first-stob*)
(set! *first-stob* stob)
(set-image-location-next! *last-stob* stob))
(set! *last-stob* new)
(set-image-location-next! new false)
(table-set! *stob-table* stob new)
(if (resumer-record? stob)
(set! *resumer-count* (+ *resumer-count* 1)))
(finalize-new-image-object stob)))
new-descriptor))
; Return the value of THING in the image. If there has been an error the
; table is gone and we proceed without doing anything.
(define (image-descriptor thing)
(if (stob? thing)
(let ((have (table-ref *stob-table* thing)))
(if (null-pointer? have)
(error "traced object has no descriptor in image"))
(image-location-new-descriptor have))
thing))
;----------------------------------------------------------------
; Walk the list of objects in the image, tracing the contents of each
; (which may add more objects to the list). The tables are traced at
; the end and are left off of the list of image objects because they
; have to be written out in a nonstandard way.
(define (make-image)
(let loop ((stob *first-stob*))
(trace-contents stob)
(if (table-okay? *stob-table*)
(let ((next (image-location-next (table-ref *stob-table* stob))))
(if (stob? next)
(loop next)))))
(let ((last *last-stob*))
(note-traced-last-stob!)
(trace-image-value (s48-symbol-table))
(trace-image-value (s48-imported-bindings))
(trace-image-value (s48-exported-bindings))
(set-image-location-next! last false))
(set! *resumer-records*
(image-alloc (enum area-type-size small) (cells->a-units *resumer-count*)))
(adjust-descriptors! *stob-table*))
(define (trace-contents stob)
(let ((header (stob-header stob)))
(if (not (or (b-vector-header? header)
(vm-eq? header weak-pointer-header)))
(let* ((start (address-after-header stob))
(end (address+ start (header-length-in-a-units header))))
(do ((addr start (address1+ addr)))
((address= addr end))
(trace-image-value (fetch addr)))
(unspecific)))))
; The exported binding table does not contain normal pointers. This does
; the appropriate magic for finding the objects it contains.
(define trace-exported-bindings
(let ((walker (table-walker shared-binding-next)))
(lambda (table)
(walker (lambda (binding)
(trace-image-value binding))
table))))
;----------------------------------------------------------------
; Actually write out the image. This is follows the same sequence as
; MAKE-IMAGE.
(define (write-image)
(write-image-areas *first-stob* *stob-table* write-stob)
(write-symbol-table (s48-symbol-table))
(write-shared-table (s48-imported-bindings))
(write-shared-table (s48-exported-bindings))
(write-resumer-records))
(define (write-stob stob)
(cond ((weak-pointer? stob)
(write-descriptor weak-pointer-header)
(if (image-extant? (weak-pointer-ref stob))
(write-descriptor (image-descriptor (weak-pointer-ref stob)))
(write-descriptor false)))
((channel? stob)
(write-channel stob))
((vm-symbol? stob)
(write-symbol stob))
((shared-binding? stob)
(write-shared stob))
(else
(let* ((header (stob-header stob))
(start (address-after-header stob)))
(write-descriptor header)
(if (b-vector-header? header)
(write-image-block start (header-length-in-a-units header))
(write-descriptors start (header-length-in-cells header)))))))
(define (write-descriptors start cells)
(let ((end (address+ start (cells->a-units cells))))
(do ((addr start (address1+ addr)))
((address= addr end))
(write-descriptor (image-descriptor (fetch addr))))
(unspecific)))
; Walk the list of objects one last time to find the resumer records.
(define (write-resumer-records)
(write-descriptor (make-header (enum stob vector)
(cells->bytes *resumer-count*)))
(let loop ((stob *first-stob*))
(if (stob? stob)
(let ((location (table-ref *stob-table* stob)))
(if (resumer-record? stob)
(write-descriptor (image-location-new-descriptor location)))
(loop (image-location-next location))))))
; Write out as closed. The status is the first slot, for what it's worth.
; It would be nice to clobber the os-index as well, but I don't want to add
; any extra assumptions here about what is where.
(define (write-channel channel)
(let ((header (stob-header channel)))
(write-descriptor header)
(write-descriptor closed-status)
(write-descriptors (address1+ (address-after-header channel))
(- (header-length-in-cells header) 1))
(write-error-string "Channel closed in dumped image: ")
(let ((id (channel-id channel)))
(if (fixnum? id)
(write-error-integer (extract-fixnum id))
(write-error-string (extract-low-string id)))
(write-error-newline))
(unspecific)))
(define closed-status
(enter-fixnum (enum channel-status-option closed)))
; The value of the next field is disguised as a non-pointer to fool the GC.
; We have to follow it until we find the next symbol that is in the image.
(define (write-symbol symbol)
(let ((header (stob-header symbol))
(next (next-extant-symbol (link->value (vm-symbol-next symbol)))))
(write-descriptor header)
(write-descriptors (address-after-header symbol)
(- (header-length-in-cells header) 1))
(write-descriptor (value->link (image-descriptor next)))))
(define (next-extant-symbol symbol)
(do ((next symbol (link->value (vm-symbol-next next))))
((image-extant? next)
next)))
; Follow next, which is another disguised pointer. We drop the value of
; imports. The old value will still be in the image, but it's only a
; pointer-sized byte vector.
(define (write-shared shared)
(let ((header (stob-header shared))
(next (next-extant-shared (link->value (shared-binding-next shared)))))
(write-descriptor header)
(write-descriptors (address-after-header shared)
(- (header-length-in-cells header) 2))
(write-descriptor (if (vm-eq? (shared-binding-is-import? shared)
true)
unassigned-marker
(image-descriptor (shared-binding-ref shared))))
(write-descriptor (value->link (image-descriptor next)))))
(define (next-extant-shared shared)
(do ((next shared (link->value (shared-binding-next next))))
((image-extant? next)
next)))
; More disguised pointers.
(define (table-writer next)
(lambda (table)
(write-descriptor (stob-header table))
(do ((i 0 (+ i 1)))
((= i (vm-vector-length table)))
(write-descriptor
(value->link (image-descriptor
(next (link->value (vm-vector-ref table i)))))))))
(define write-symbol-table (table-writer next-extant-symbol))
(define write-shared-table (table-writer next-extant-shared))
;----------------
; Undumpable records
;
; Record types may be marked as `undumpable', in which case they are replaced
; in images by the value of their first slot. Any that are found are put in a
; vector provided by our caller for that purpose. They are eventually reported
; back to the user.
(define (undumpable? x)
(and (gc-record? x)
(let ((type (record-ref x 0)))
(and (gc-record? type)
(= false (record-ref type 1))))))
(define (gc-record? x)
(and (stob? x)
(let ((header (stob-header x)))
(if (stob? header)
(record? header)
(record? x)))))
(define (undumpable-alias record)
(record-ref record 1))
; We add undumpable records to a vector provided by the caller.
(define (note-undumpable! thing)
(if (and (< *undumpable-count*
(vm-vector-length *undumpable-records*))
(not (vector-memq? thing *undumpable-records*)))
(begin
(vm-vector-set! *undumpable-records*
*undumpable-count*
thing)
(set! *undumpable-count* (+ 1 *undumpable-count*)))))
(define (vector-memq? thing vector)
(let ((len (vm-vector-length vector)))
(let loop ((i 0))
(cond ((= i len)
#f)
((vm-eq? (vm-vector-ref vector i) thing)
#t)
(else
(loop (+ i 1)))))))
;----------------------------------------------------------------
; More abstraction breaking, this time for finding records whose type has
; a resumer method.
(define (resumer-record? stob)
(and (record? stob)
(let ((type (record-type stob)))
(and (record? type)
(stob? (record-type-resumer type))))))
; A record's type is at offset 0 and a type's resumer is at offset 1.
(define (record-type record)
(record-ref record 0))
(define (record-type-resumer record-type)
(record-ref record-type 1))
;----------------------------------------------------------------
; Used to detect weak pointers.
(define weak-pointer-header
(make-header (enum stob weak-pointer)
(cells->bytes (- weak-pointer-size 1))))
|