127 lines
5.0 KiB
C
127 lines
5.0 KiB
C
/**************************************************************************/
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/* */
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/* OCaml */
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/* */
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/* Damien Doligez, projet Para, INRIA Rocquencourt */
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/* */
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/* Copyright 1996 Institut National de Recherche en Informatique et */
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/* en Automatique. */
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/* */
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/* All rights reserved. This file is distributed under the terms of */
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/* the GNU Lesser General Public License version 2.1, with the */
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/* special exception on linking described in the file LICENSE. */
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/* */
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/**************************************************************************/
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/* Classification of addresses for GC and runtime purposes. */
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/* The current runtime supports two different configurations that
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correspond to two different value models, depending on whether
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"naked pointers", that do not point to a well-formed OCaml block,
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are allowed (considered valid values).
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In "classic mode", naked pointers are allowed, and the
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implementation uses a page table. A valid value is then either:
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- a tagged integer (Is_long or !Is_block from mlvalues.h)
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- a pointer to the minor heap (Is_young)
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- a pointer to the major heap (Is_in_heap)
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- a pointer to a constant block statically-allocated by OCaml code
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or the OCaml runtime (Is_in_static_data)
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- a "foreign" pointer, which is none of the above; the destination
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of those pointers may be a well-formed OCaml blocks, but it may
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also be a naked pointer.
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The macros and functions below give access to a global page table
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to classify addresses to be able to implement Is_in_heap,
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In_static_data (or their disjunction Is_in_value_area) and thus
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detect values which may be naked pointers. The runtime
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conservatively assumes that all foreign pointers may be naked
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pointers, and uses the page table to not dereference/follow them.
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In "no naked pointers" mode (when NO_NAKED_POINTERS is defined),
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naked pointers are illegal, so pointers that are values can always
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be assumed to point to well-formed blocks.
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To support an implementation without a global page table, runtime
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code should not rely on Is_in_heap and Is_in_static_data. This
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corresponds to a simpler model where a valid value is either:
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- a tagged integer (Is_long)
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- a pointer to the minor heap (Is_young)
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- a pointer to a well-formed block outside the minor heap
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(it may be in the major heap, or static, or a foreign pointer,
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without a check to distinguish the various cases).
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(To create a well-formed block outside the heap that the GC will
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not scan, one can use the Caml_out_of_heap_header from mlvalues.h.)
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*/
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#ifndef CAML_ADDRESS_CLASS_H
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#define CAML_ADDRESS_CLASS_H
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#include "config.h"
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#include "misc.h"
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#include "mlvalues.h"
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/* Use the following macros to test an address for the different classes
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it might belong to. */
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#define Is_young(val) \
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(CAMLassert (Is_block (val)), \
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(char *)(val) < (char *)Caml_state_field(young_end) && \
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(char *)(val) > (char *)Caml_state_field(young_start))
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#define Is_in_heap(a) (Classify_addr(a) & In_heap)
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#ifdef NO_NAKED_POINTERS
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#define Is_in_heap_or_young(a) 1
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#define Is_in_value_area(a) 1
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#else
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#define Is_in_heap_or_young(a) (Classify_addr(a) & (In_heap | In_young))
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#define Is_in_value_area(a) \
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(Classify_addr(a) & (In_heap | In_young | In_static_data))
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#define Is_in_static_data(a) (Classify_addr(a) & In_static_data)
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#endif
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/***********************************************************************/
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/* The rest of this file is private and may change without notice. */
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#define Not_in_heap 0
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#define In_heap 1
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#define In_young 2
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#define In_static_data 4
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#ifdef ARCH_SIXTYFOUR
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/* 64 bits: Represent page table as a sparse hash table */
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int caml_page_table_lookup(void * addr);
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#define Classify_addr(a) (caml_page_table_lookup((void *)(a)))
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#else
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/* 32 bits: Represent page table as a 2-level array */
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#define Pagetable2_log 11
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#define Pagetable2_size (1 << Pagetable2_log)
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#define Pagetable1_log (Page_log + Pagetable2_log)
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#define Pagetable1_size (1 << (32 - Pagetable1_log))
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CAMLextern unsigned char * caml_page_table[Pagetable1_size];
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#define Pagetable_index1(a) (((uintnat)(a)) >> Pagetable1_log)
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#define Pagetable_index2(a) \
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((((uintnat)(a)) >> Page_log) & (Pagetable2_size - 1))
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#define Classify_addr(a) \
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caml_page_table[Pagetable_index1(a)][Pagetable_index2(a)]
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#endif
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int caml_page_table_add(int kind, void * start, void * end);
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int caml_page_table_remove(int kind, void * start, void * end);
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int caml_page_table_initialize(mlsize_t bytesize);
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#endif /* CAML_ADDRESS_CLASS_H */
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