These macros might not be defined, in which case this usage would have generated warnings had they not been in system headers.
683 lines
16 KiB
C++
683 lines
16 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
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This file is part of the Sortix C Library.
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The Sortix C Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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The Sortix C Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
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stdlib/heap.cpp
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Functions that allocate/free memory from a dynamic memory heap.
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*******************************************************************************/
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#include <sys/mman.h>
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#if __STDC_HOSTED__
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#include <error.h>
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#include <stdio.h>
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#include <unistd.h>
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#endif
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#include <assert.h>
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#include <errno.h>
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#include <malloc.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#define PARANOIA 1
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#if defined(__is_sortix_kernel)
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#include <sortix/kernel/decl.h>
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#include <sortix/kernel/addralloc.h>
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#include <sortix/kernel/kthread.h>
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#include <sortix/kernel/log.h>
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#include <sortix/kernel/memorymanagement.h>
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#include <sortix/kernel/panic.h>
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#endif
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//
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// This first section is just magic compiler/platform stuff, you should
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// skip ahead to the actual algorithm.
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//
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#if defined(__x86_64__)
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const size_t MAGIC = 0xDEADDEADDEADDEADUL;
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const size_t ALIGNMENT = 16UL;
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#else
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const size_t MAGIC = 0xDEADDEADUL;
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const size_t ALIGNMENT = 8UL;
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#endif
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const size_t PAGESIZE = 4UL * 1024UL; // 4 KiB
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const size_t NUMBINS = 8UL * sizeof(size_t);
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static uintptr_t wilderness;
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#if defined(__is_sortix_kernel)
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static uintptr_t GetHeapStart()
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{
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return Sortix::GetHeapLower();
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}
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static void FreeMemory(uintptr_t where, size_t bytes)
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{
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assert(Sortix::Page::IsAligned(where + bytes));
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while ( bytes )
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{
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addr_t page = Sortix::Memory::Unmap(where);
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Sortix::Page::Put(page);
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bytes -= PAGESIZE;
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where += PAGESIZE;
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}
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}
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static bool AllocateMemory(uintptr_t where, size_t bytes)
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{
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assert(Sortix::Page::IsAligned(where + bytes));
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uintptr_t pos = where;
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while ( bytes )
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{
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addr_t page = Sortix::Page::Get();
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if ( !page )
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{
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FreeMemory(where, pos-where);
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return false;
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}
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if ( !Sortix::Memory::Map(page, pos, PROT_KREAD | PROT_KWRITE) )
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{
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Sortix::Page::Put(page);
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FreeMemory(where, pos-where);
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return false;
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}
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bytes -= PAGESIZE;
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pos += PAGESIZE;
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}
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return true;
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}
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static bool ExtendHeap(size_t bytesneeded)
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{
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size_t got_bytes = Sortix::ExpandHeap(bytesneeded);
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if ( !got_bytes )
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return false;
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assert(bytesneeded <= got_bytes);
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if ( !AllocateMemory(wilderness, got_bytes) )
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{
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Sortix::ShrinkHeap(got_bytes);
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return false;
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}
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return true;
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}
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#else
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static uintptr_t GetHeapStart()
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{
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uintptr_t base = (uintptr_t) sbrk(0);
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uintptr_t unaligned = base % ALIGNMENT;
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if ( unaligned )
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{
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sbrk(ALIGNMENT-unaligned);
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}
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uintptr_t result = (uintptr_t) sbrk(0);
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return result;
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}
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static bool ExtendHeap(size_t bytesneeded)
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{
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void* newheapend = sbrk(bytesneeded);
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return newheapend != (void*) -1UL;
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}
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#endif
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// TODO: BitScanForward and BitScanReverse are x86 instructions, but
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// directly using them messes with the optimizer. Once possible, use
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// the inline assembly instead of the C-version of the functions.
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// Returns the index of the most significant set bit.
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inline size_t BSR(size_t Value)
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{
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#if 1
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assert(Value > 0);
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for ( size_t I = 8*sizeof(size_t); I > 0; I-- )
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{
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if ( Value & ( 1UL << (I-1) ) ) { return I-1; }
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}
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return 0;
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#else
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size_t Result;
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asm("bsr %0, %1" : "=r"(Result) : "r"(Value));
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return Result;
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#endif
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}
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// Returns the index of the least significant set bit.
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inline size_t BSF(size_t Value)
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{
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#if 1
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assert(Value > 0);
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for ( size_t I = 0; I < 8*sizeof(size_t); I++ )
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{
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if ( Value & ( 1UL << I ) ) { return I; }
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}
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return 0;
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#else
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size_t Result;
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asm("bsf %0, %1" : "=r"(Result) : "r"(Value));
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return Result;
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#endif
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}
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//
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// Now for some helper functions and structures.
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//
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struct Chunk;
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struct Trailer;
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#if defined(__is_sortix_kernel)
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Sortix::kthread_mutex_t heaplock;
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#endif
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// The location where the heap originally grows from.
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uintptr_t heapstart;
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// If heap grows down: Location of the first mapped page.
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// If heap grows up: Location of the first not-mapped page.
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#if 0 /* forward declared abvce */
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static uintptr_t wilderness;
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#endif
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// How many bytes remain in the wilderness.
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size_t wildernesssize;
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// How many bytes are the heap allow to grow to (including wilderness).
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size_t heapmaxsize;
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// How many bytes are currently used for chunks in the heap, which
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// excludes the wilderness.
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size_t heapsize;
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// bins[N] contain a linked list of chunks that are at least 2^(N+1)
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// bytes, but less than 2^(N+2) bytes. By selecting the proper bin in
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// constant time, we can allocate chunks in constant time.
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Chunk* bins[NUMBINS];
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// Bit N is set if bin[N] contains a chunk.
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size_t bincontainschunks;
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static bool IsGoodHeapPointer(void* ptr, size_t size)
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{
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uintptr_t ptrlower = (uintptr_t) ptr;
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uintptr_t ptrupper = ptrlower + size;
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uintptr_t heaplower = heapstart;
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uintptr_t heapupper = wilderness;
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return heaplower <= ptrlower && ptrupper <= heapupper;
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}
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// A preamble to every chunk providing meta-information.
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struct Chunk
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{
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public:
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size_t size; // Includes size of Chunk and Trailer
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union
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{
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size_t magic;
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Chunk* nextunused;
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};
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public:
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bool IsUsed() { return magic == MAGIC; }
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Trailer* GetTrailer();
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Chunk* LeftNeighbor();
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Chunk* RightNeighbor();
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bool IsSane();
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};
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// A trailer to every chunk providing meta-information.
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struct Trailer
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{
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public:
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union
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{
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size_t magic;
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Chunk* prevunused;
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};
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size_t size; // Includes size of Chunk and Trailer
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public:
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bool IsUsed() { return magic == MAGIC; }
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Chunk* GetChunk();
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};
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const size_t OVERHEAD = sizeof(Chunk) + sizeof(Trailer);
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// This is how a real chunk actually looks:
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//struct RealChunk
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//{
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// Chunk header;
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// byte data[...];
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// Trailer footer;
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// };
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Trailer* Chunk::GetTrailer()
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{
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return (Trailer*) (((uintptr_t) this) + size - sizeof(Trailer));
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}
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Chunk* Chunk::LeftNeighbor()
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{
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Trailer* trailer = (Trailer*) (((uintptr_t) this) - sizeof(Trailer));
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return trailer->GetChunk();
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}
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Chunk* Chunk::RightNeighbor()
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{
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return (Chunk*) (((uintptr_t) this) + size);
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}
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Chunk* Trailer::GetChunk()
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{
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return (Chunk*) (((uintptr_t) this) + sizeof(Trailer) - size);
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}
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bool Chunk::IsSane()
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{
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if ( !IsGoodHeapPointer(this, sizeof(*this)) )
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return false;
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if ( !size ) { return false; }
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size_t binindex = BSR(size);
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Trailer* trailer = GetTrailer();
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if ( !IsGoodHeapPointer(trailer, sizeof(*trailer)) )
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return false;
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if ( trailer->size != size ) { return false; }
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if ( IsUsed() )
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{
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if ( bins[binindex] == this ) { return false; }
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if ( magic != MAGIC || trailer->magic != magic ) { return false; }
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}
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if ( !IsUsed() )
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{
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if ( ((uintptr_t) nextunused) & (ALIGNMENT-1UL) ) { return false; }
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if ( ((uintptr_t) trailer->prevunused) & (ALIGNMENT-1UL) ) { return false; }
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if ( nextunused && !IsGoodHeapPointer(nextunused->GetTrailer(),
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sizeof(Trailer)) )
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return false;
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if ( nextunused && nextunused->GetTrailer()->prevunused != this ) { return false; }
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if ( trailer->prevunused )
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{
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if ( !IsGoodHeapPointer(trailer->prevunused,
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sizeof(*trailer->prevunused)) )
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return false;
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if ( bins[binindex] == this ) { return false; }
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if ( trailer->prevunused->nextunused != this ) { return false; }
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}
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if ( !trailer->prevunused )
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{
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if ( bins[binindex] != this ) { return false; }
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if ( !(bincontainschunks & (1UL << binindex)) ) { return false; }
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}
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}
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return true;
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}
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static void InsertChunk(Chunk* chunk)
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{
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// Insert the chunk into the right bin.
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size_t binindex = BSR(chunk->size);
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chunk->GetTrailer()->prevunused = NULL;
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chunk->nextunused = bins[binindex];
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if ( chunk->nextunused )
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{
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assert(chunk->nextunused->IsSane());
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chunk->nextunused->GetTrailer()->prevunused = chunk;
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}
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bins[binindex] = chunk;
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bincontainschunks |= (1UL << binindex);
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assert(chunk->IsSane());
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}
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__attribute__((unused))
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static bool ValidateHeap()
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{
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bool foundbin[NUMBINS];
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for ( size_t i = 0; i < NUMBINS; i++ ) { foundbin[i] = false; }
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Chunk* chunk = (Chunk*) heapstart;
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while ( (uintptr_t) chunk < wilderness - wildernesssize )
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{
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size_t timesfound = 0;
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for ( size_t i = 0; i < NUMBINS; i++ )
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{
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if ( chunk == bins[i] ) { foundbin[i] = true; timesfound++; }
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}
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if ( 1 < timesfound ) { return false; }
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if ( !chunk->IsSane() ) { return false; }
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chunk = chunk->RightNeighbor();
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}
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for ( size_t i = 0; i < NUMBINS; i++ )
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{
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if ( !bins[i] )
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{
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if ( foundbin[i] ) { return false; }
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continue;
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}
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if ( !foundbin[i] ) { return false; }
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if ( !bins[i]->IsSane() ) { return false; }
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}
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return true;
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}
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//
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// This is where the actual memory allocation algorithm starts.
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//
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extern "C" void _init_heap()
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{
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heapstart = GetHeapStart();
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heapmaxsize = SIZE_MAX;
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heapsize = 0;
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wilderness = heapstart;
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wildernesssize = 0;
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for ( size_t i = 0; i < NUMBINS; i++ ) { bins[i] = NULL; }
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bincontainschunks = 0;
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#if defined(__is_sortix_kernel)
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heaplock = Sortix::KTHREAD_MUTEX_INITIALIZER;
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#endif
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}
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// Attempts to expand the wilderness such that it contains at least
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// bytesneeded bytes. This is done by mapping new pages onto into the
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// virtual address-space.
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static bool ExpandWilderness(size_t bytesneeded)
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{
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if ( bytesneeded <= wildernesssize ) { return true; }
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bytesneeded -= wildernesssize;
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// Align the increase on page boundaries.
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const size_t PAGEMASK = ~(PAGESIZE - 1UL);
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bytesneeded = ( bytesneeded + PAGESIZE - 1UL ) & PAGEMASK;
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assert(bytesneeded >= PAGESIZE);
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// TODO: Overflow MAY happen here!
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if ( heapmaxsize <= heapsize + wildernesssize + bytesneeded )
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return errno = ENOMEM, true;
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uintptr_t newwilderness = wilderness + bytesneeded;
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// Attempt to map pages so our wilderness grows.
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if ( !ExtendHeap(bytesneeded) )
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return false;
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wildernesssize += bytesneeded;
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wilderness = newwilderness;
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return true;
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}
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extern "C" void* malloc(size_t size)
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{
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#if defined(__is_sortix_kernel)
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Sortix::ScopedLock scopedlock(&heaplock);
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#endif
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#if 2 <= PARANOIA
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assert(ValidateHeap());
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#endif
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// The size field keeps both the allocation and meta information.
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size += OVERHEAD;
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// Round up to nearest alignment.
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size = (size + ALIGNMENT - 1UL) & (~(ALIGNMENT-1UL));
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// Find the index of the smallest usable bin.
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size_t minbinindex = BSR(size-1UL)+1UL;
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// Make a bitmask that filter away all bins that are too small.
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size_t minbinmask = ~((1UL << minbinindex) - 1UL);
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// Figure out which bins are usable for our chunk.
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size_t availablebins = bincontainschunks & minbinmask;
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if ( availablebins )
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{
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// Find the smallest available bin.
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size_t binindex = BSF(availablebins);
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Chunk* chunk = bins[binindex];
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assert(chunk->IsSane());
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bins[binindex] = chunk->nextunused;
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size_t binsize = 1UL << binindex;
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// Mark the bin as empty if we emptied it.
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if ( !bins[binindex] )
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{
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bincontainschunks ^= binsize;
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}
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else
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{
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Trailer* trailer = bins[binindex]->GetTrailer();
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trailer->prevunused = NULL;
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}
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assert(!bins[binindex] || bins[binindex]->IsSane());
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// If we don't use the entire chunk.
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if ( OVERHEAD <= binsize - size )
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{
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size_t left = binsize - size;
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chunk->size -= left;
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chunk->GetTrailer()->size = chunk->size;
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Chunk* leftchunk = chunk->RightNeighbor();
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leftchunk->size = left;
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Trailer* lefttrailer = leftchunk->GetTrailer();
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lefttrailer->size = left;
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InsertChunk(leftchunk);
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}
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chunk->magic = MAGIC;
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chunk->GetTrailer()->magic = MAGIC;
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#if 3 <= PARANOIA
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assert(ValidateHeap());
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#endif
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uintptr_t result = ((uintptr_t) chunk) + sizeof(Chunk);
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return (void*) result;
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}
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// If no bins are available, try to allocate from the wilderness.
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// Check if the wilderness can meet our requirements.
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if ( wildernesssize < size && !ExpandWilderness(size) )
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{
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errno = ENOMEM;
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return NULL;
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}
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// Carve a new chunk out of the wilderness and initialize it.
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Chunk* chunk = (Chunk*) (wilderness - wildernesssize);
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assert(size <= wildernesssize);
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wildernesssize -= size;
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heapsize += size;
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assert(IsGoodHeapPointer(chunk, sizeof(*chunk)));
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chunk->size = size;
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Trailer* trailer = chunk->GetTrailer();
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assert(IsGoodHeapPointer(trailer, sizeof(*trailer)));
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trailer->size = size;
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chunk->magic = MAGIC;
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trailer->magic = MAGIC;
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#if 3 <= PARANOIA
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assert(ValidateHeap());
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#endif
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uintptr_t result = ((uintptr_t) chunk) + sizeof(Chunk);
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return (void*) result;
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}
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static bool IsLeftmostChunk(Chunk* chunk)
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{
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return heapstart <= (uintptr_t) chunk;
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}
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static bool IsRightmostChunk(Chunk* chunk)
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{
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return heapstart + heapsize <= (uintptr_t) chunk + chunk->size;
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}
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// Removes a chunk from its bin.
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static void UnlinkChunk(Chunk* chunk)
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{
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assert(chunk->IsSane());
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Trailer* trailer = chunk->GetTrailer();
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if ( trailer->prevunused )
|
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{
|
|
assert(trailer->prevunused->IsSane());
|
|
trailer->prevunused->nextunused = chunk->nextunused;
|
|
if ( chunk->nextunused )
|
|
{
|
|
assert(chunk->nextunused->IsSane());
|
|
chunk->nextunused->GetTrailer()->prevunused = trailer->prevunused;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
if ( chunk->nextunused )
|
|
{
|
|
assert(chunk->nextunused->IsSane());
|
|
chunk->nextunused->GetTrailer()->prevunused = NULL;
|
|
}
|
|
size_t binindex = BSR(chunk->size);
|
|
assert(bins[binindex] == chunk);
|
|
bins[binindex] = chunk->nextunused;
|
|
if ( !bins[binindex] ) { bincontainschunks ^= 1UL << binindex; }
|
|
else { assert(bins[binindex]->IsSane()); }
|
|
}
|
|
}
|
|
|
|
// Transforms a chunk and its neighbors into a single chunk if possible.
|
|
static void UnifyNeighbors(Chunk** chunk)
|
|
{
|
|
if ( !IsLeftmostChunk(*chunk) )
|
|
{
|
|
Chunk* neighbor = (*chunk)->LeftNeighbor();
|
|
if ( !neighbor->IsUsed() )
|
|
{
|
|
size_t size = neighbor->size;
|
|
size_t chunksize = (*chunk)->size;
|
|
UnlinkChunk(neighbor);
|
|
*chunk = neighbor;
|
|
(*chunk)->size = size + chunksize;
|
|
(*chunk)->GetTrailer()->size = (*chunk)->size;
|
|
}
|
|
}
|
|
|
|
if ( !IsRightmostChunk(*chunk) )
|
|
{
|
|
Chunk* neighbor = (*chunk)->RightNeighbor();
|
|
if ( !neighbor->IsUsed() )
|
|
{
|
|
UnlinkChunk(neighbor);
|
|
(*chunk)->size += neighbor->size;
|
|
(*chunk)->GetTrailer()->size = (*chunk)->size;
|
|
}
|
|
}
|
|
}
|
|
|
|
extern "C" void free(void* addr)
|
|
{
|
|
#if defined(__is_sortix_kernel)
|
|
Sortix::ScopedLock scopedlock(&heaplock);
|
|
#endif
|
|
|
|
#if 2 <= PARANOIA
|
|
assert(ValidateHeap());
|
|
#endif
|
|
|
|
if ( !addr) { return; }
|
|
Chunk* chunk = (Chunk*) ((uintptr_t) addr - sizeof(Chunk));
|
|
#if __STDC_HOSTED__
|
|
if ( !IsGoodHeapPointer(addr, 1) ||
|
|
!IsGoodHeapPointer(chunk, sizeof(*chunk)) )
|
|
{
|
|
error(0, 0, "attempted to free(3) non-heap pointer: 0x%zx", addr);
|
|
abort();
|
|
}
|
|
if ( !chunk->IsUsed() )
|
|
{
|
|
error(0, 0, "attempted to free(3) area that doesn't appear to be "
|
|
"allocated: 0x%zx + 0x%zx", addr);
|
|
abort();
|
|
}
|
|
#endif
|
|
assert(chunk->IsUsed());
|
|
assert(chunk->IsSane());
|
|
|
|
UnifyNeighbors(&chunk);
|
|
|
|
bool nexttowilderness = IsRightmostChunk(chunk);
|
|
|
|
// If possible, let the wilderness regain the memory.
|
|
if ( nexttowilderness )
|
|
{
|
|
heapsize -= chunk->size;
|
|
wildernesssize += chunk->size;
|
|
return;
|
|
}
|
|
|
|
InsertChunk(chunk);
|
|
|
|
#if 3 <= PARANOIA
|
|
assert(ValidateHeap());
|
|
#endif
|
|
}
|
|
|
|
// TODO: Implement this function properly.
|
|
extern "C" void* realloc(void* ptr, size_t size)
|
|
{
|
|
if ( !ptr ) { return malloc(size); }
|
|
Chunk* chunk = (Chunk*) ((uintptr_t) ptr - sizeof(Chunk));
|
|
assert(chunk->IsUsed());
|
|
assert(chunk->IsSane());
|
|
size_t allocsize = chunk->size - OVERHEAD;
|
|
if ( size < allocsize ) { return ptr; }
|
|
void* newptr = malloc(size);
|
|
if ( !newptr ) { return NULL; }
|
|
memcpy(newptr, ptr, allocsize);
|
|
free(ptr);
|
|
return newptr;
|
|
}
|