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Nunuhara Cabbage
851a19acc1
ref types are currently passed to HLL functions as pointers into the heap. If the HLL function itself needs to allocate memory from the heap, it can cause the heap to be reallocated, rendering these heap pointers invalid. In order to work around this, hll_call now guarantees 64 slots are available on the heap before calling any HLL function. This is not a great solution, but it should work to the extent that HLL functions only allocate a fixed number of heap slots < 64. This bug could be easily triggered by scrolling up on the message log in Sengoku Rance.
83 lines
2.0 KiB
C
83 lines
2.0 KiB
C
/* Copyright (C) 2019 Nunuhara Cabbage <nunuhara@haniwa.technology>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://gnu.org/licenses/>.
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*/
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#ifndef SYSTEM4_HEAP_H
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#define SYSTEM4_HEAP_H
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#include <stdbool.h>
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#include <stddef.h>
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#include <stdint.h>
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struct string;
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struct page;
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enum vm_pointer_type {
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VM_PAGE,
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VM_STRING
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};
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#define NR_VM_POINTER_TYPES (VM_STRING+1)
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// Heap-backed objects. Reference counted.
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struct vm_pointer {
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int ref;
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enum vm_pointer_type type;
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union {
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struct string *s;
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struct page *page;
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};
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#ifdef DEBUG_HEAP
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size_t alloc_addr;
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size_t ref_addr;
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size_t free_addr;
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#endif
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};
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extern struct vm_pointer *heap;
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extern size_t heap_size;
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void heap_init(void);
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void heap_delete(void);
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int32_t heap_alloc_slot(enum vm_pointer_type type);
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void heap_ref(int slot);
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void heap_unref(int slot);
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void exit_unref(int slot);
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bool heap_index_valid(int index);
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bool page_index_valid(int index);
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bool string_index_valid(int index);
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struct page *heap_get_page(int index);
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struct string *heap_get_string(int index);
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void heap_set_page(int slot, struct page *page);
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/*
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* Guarantee `headroom` free slots are available on the heap.
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*
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* XXX: this is a hack to fix an issue with HLL calls where a pointer into the
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* heap can be made invalid by a heap reallocation triggered within the
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* body of the HLL function.
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*/
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void heap_guarantee(unsigned headroom);
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#ifdef VM_PRIVATE
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extern int32_t *heap_free_stack;
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extern size_t heap_free_ptr;
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#endif /* VM_PRIVATE */
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#endif /* SYSTEM4_HEAP_H */
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