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339 lines
9.1 KiB
C++
339 lines
9.1 KiB
C++
// -*- C++ -*- Allocate exception objects.
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// Copyright (C) 2001-2022 Free Software Foundation, Inc.
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//
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// This file is part of GCC.
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//
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// GCC 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 3, or (at your option)
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// any later version.
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//
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// GCC 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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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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// This is derived from the C++ ABI for IA-64. Where we diverge
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// for cross-architecture compatibility are noted with "@@@".
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#include <bits/c++config.h>
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#include <cstdlib>
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#if _GLIBCXX_HOSTED
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#include <cstring>
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#endif
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#include <climits>
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#include <exception>
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#include "unwind-cxx.h"
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#include <ext/concurrence.h>
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#include <new>
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#if _GLIBCXX_HOSTED
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using std::free;
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using std::malloc;
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using std::memset;
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#else
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// In a freestanding environment, these functions may not be available
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// -- but for now, we assume that they are.
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extern "C" void *malloc (std::size_t);
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extern "C" void free(void *);
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extern "C" void *memset (void *, int, std::size_t);
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#endif
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using namespace __cxxabiv1;
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// ??? How to control these parameters.
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// Guess from the size of basic types how large a buffer is reasonable.
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// Note that the basic c++ exception header has 13 pointers and 2 ints,
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// so on a system with PSImode pointers we're talking about 56 bytes
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// just for overhead.
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#if INT_MAX == 32767
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# define EMERGENCY_OBJ_SIZE 128
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# define EMERGENCY_OBJ_COUNT 16
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#elif !defined (_GLIBCXX_LLP64) && LONG_MAX == 2147483647
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# define EMERGENCY_OBJ_SIZE 512
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# define EMERGENCY_OBJ_COUNT 32
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#else
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# define EMERGENCY_OBJ_SIZE 1024
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# define EMERGENCY_OBJ_COUNT 64
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#endif
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#ifndef __GTHREADS
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# undef EMERGENCY_OBJ_COUNT
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# define EMERGENCY_OBJ_COUNT 4
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#endif
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namespace __gnu_cxx
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{
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void __freeres();
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}
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namespace
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{
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// A fixed-size heap, variable size object allocator
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class pool
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{
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public:
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pool();
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_GLIBCXX_NODISCARD void *allocate (std::size_t);
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void free (void *);
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bool in_pool (void *);
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private:
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struct free_entry {
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std::size_t size;
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free_entry *next;
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};
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struct allocated_entry {
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std::size_t size;
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char data[] __attribute__((aligned));
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};
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// A single mutex controlling emergency allocations.
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__gnu_cxx::__mutex emergency_mutex;
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// The free-list
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free_entry *first_free_entry;
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// The arena itself - we need to keep track of these only
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// to implement in_pool.
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char *arena;
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std::size_t arena_size;
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friend void __gnu_cxx::__freeres();
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};
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pool::pool()
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{
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// Allocate the arena - we could add a GLIBCXX_EH_ARENA_SIZE environment
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// to make this tunable.
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arena_size = (EMERGENCY_OBJ_SIZE * EMERGENCY_OBJ_COUNT
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+ EMERGENCY_OBJ_COUNT * sizeof (__cxa_dependent_exception));
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arena = (char *)malloc (arena_size);
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if (!arena)
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{
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// If the allocation failed go without an emergency pool.
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arena_size = 0;
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first_free_entry = NULL;
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return;
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}
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// Populate the free-list with a single entry covering the whole arena
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first_free_entry = reinterpret_cast <free_entry *> (arena);
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new (first_free_entry) free_entry;
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first_free_entry->size = arena_size;
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first_free_entry->next = NULL;
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}
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void *pool::allocate (std::size_t size)
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{
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__gnu_cxx::__scoped_lock sentry(emergency_mutex);
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// We need an additional size_t member plus the padding to
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// ensure proper alignment of data.
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size += offsetof (allocated_entry, data);
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// And we need to at least hand out objects of the size of
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// a freelist entry.
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if (size < sizeof (free_entry))
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size = sizeof (free_entry);
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// And we need to align objects we hand out to the maximum
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// alignment required on the target (this really aligns the
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// tail which will become a new freelist entry).
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size = ((size + __alignof__ (allocated_entry::data) - 1)
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& ~(__alignof__ (allocated_entry::data) - 1));
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// Search for an entry of proper size on the freelist.
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free_entry **e;
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for (e = &first_free_entry;
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*e && (*e)->size < size;
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e = &(*e)->next)
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;
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if (!*e)
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return NULL;
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allocated_entry *x;
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if ((*e)->size - size >= sizeof (free_entry))
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{
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// Split block if it is too large.
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free_entry *f = reinterpret_cast <free_entry *>
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(reinterpret_cast <char *> (*e) + size);
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std::size_t sz = (*e)->size;
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free_entry *next = (*e)->next;
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new (f) free_entry;
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f->next = next;
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f->size = sz - size;
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x = reinterpret_cast <allocated_entry *> (*e);
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new (x) allocated_entry;
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x->size = size;
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*e = f;
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}
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else
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{
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// Exact size match or too small overhead for a free entry.
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std::size_t sz = (*e)->size;
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free_entry *next = (*e)->next;
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x = reinterpret_cast <allocated_entry *> (*e);
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new (x) allocated_entry;
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x->size = sz;
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*e = next;
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}
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return &x->data;
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}
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void pool::free (void *data)
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{
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__gnu_cxx::__scoped_lock sentry(emergency_mutex);
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allocated_entry *e = reinterpret_cast <allocated_entry *>
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(reinterpret_cast <char *> (data) - offsetof (allocated_entry, data));
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std::size_t sz = e->size;
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if (!first_free_entry
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|| (reinterpret_cast <char *> (e) + sz
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< reinterpret_cast <char *> (first_free_entry)))
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{
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// If the free list is empty or the entry is before the
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// first element and cannot be merged with it add it as
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// the first free entry.
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free_entry *f = reinterpret_cast <free_entry *> (e);
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new (f) free_entry;
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f->size = sz;
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f->next = first_free_entry;
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first_free_entry = f;
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}
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else if (reinterpret_cast <char *> (e) + sz
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== reinterpret_cast <char *> (first_free_entry))
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{
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// Check if we can merge with the first free entry being right
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// after us.
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free_entry *f = reinterpret_cast <free_entry *> (e);
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new (f) free_entry;
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f->size = sz + first_free_entry->size;
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f->next = first_free_entry->next;
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first_free_entry = f;
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}
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else
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{
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// Else search for a free item we can merge with at its end.
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free_entry **fe;
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for (fe = &first_free_entry;
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(*fe)->next
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&& (reinterpret_cast <char *> ((*fe)->next)
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> reinterpret_cast <char *> (e) + sz);
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fe = &(*fe)->next)
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;
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// If we can merge the next block into us do so and continue
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// with the cases below.
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if (reinterpret_cast <char *> (e) + sz
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== reinterpret_cast <char *> ((*fe)->next))
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{
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sz += (*fe)->next->size;
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(*fe)->next = (*fe)->next->next;
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}
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if (reinterpret_cast <char *> (*fe) + (*fe)->size
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== reinterpret_cast <char *> (e))
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// Merge with the freelist entry.
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(*fe)->size += sz;
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else
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{
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// Else put it after it which keeps the freelist sorted.
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free_entry *f = reinterpret_cast <free_entry *> (e);
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new (f) free_entry;
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f->size = sz;
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f->next = (*fe)->next;
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(*fe)->next = f;
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}
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}
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}
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bool pool::in_pool (void *ptr)
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{
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char *p = reinterpret_cast <char *> (ptr);
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return (p > arena
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&& p < arena + arena_size);
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}
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pool emergency_pool;
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}
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namespace __gnu_cxx
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{
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void
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__freeres()
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{
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if (emergency_pool.arena)
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{
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::free(emergency_pool.arena);
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emergency_pool.arena = 0;
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}
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}
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}
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extern "C" void *
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__cxxabiv1::__cxa_allocate_exception(std::size_t thrown_size) _GLIBCXX_NOTHROW
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{
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void *ret;
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thrown_size += sizeof (__cxa_refcounted_exception);
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ret = malloc (thrown_size);
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if (!ret)
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ret = emergency_pool.allocate (thrown_size);
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if (!ret)
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std::terminate ();
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memset (ret, 0, sizeof (__cxa_refcounted_exception));
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return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
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}
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extern "C" void
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__cxxabiv1::__cxa_free_exception(void *vptr) _GLIBCXX_NOTHROW
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{
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char *ptr = (char *) vptr - sizeof (__cxa_refcounted_exception);
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if (emergency_pool.in_pool (ptr))
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emergency_pool.free (ptr);
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else
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free (ptr);
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}
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extern "C" __cxa_dependent_exception*
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__cxxabiv1::__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW
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{
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__cxa_dependent_exception *ret;
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ret = static_cast<__cxa_dependent_exception*>
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(malloc (sizeof (__cxa_dependent_exception)));
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if (!ret)
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ret = static_cast <__cxa_dependent_exception*>
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(emergency_pool.allocate (sizeof (__cxa_dependent_exception)));
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if (!ret)
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std::terminate ();
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memset (ret, 0, sizeof (__cxa_dependent_exception));
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return ret;
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}
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extern "C" void
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__cxxabiv1::__cxa_free_dependent_exception
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(__cxa_dependent_exception *vptr) _GLIBCXX_NOTHROW
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{
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if (emergency_pool.in_pool (vptr))
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emergency_pool.free (vptr);
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else
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free (vptr);
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}
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