141 lines
3.8 KiB
C++
141 lines
3.8 KiB
C++
/* heap.cc: Cygwin heap manager.
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Copyright 1996, 1997, 1998, 1999, 2000 Cygnus Solutions.
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This file is part of Cygwin.
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This software is a copyrighted work licensed under the terms of the
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Cygwin license. Please consult the file "CYGWIN_LICENSE" for
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details. */
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#include <errno.h>
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#include "winsup.h"
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#define brksize ((char *) user_data->heaptop - (char *) user_data->heapbase)
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#define brk (user_data->heapptr)
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#define brkbase (user_data->heapbase)
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#define brktop (user_data->heaptop)
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#define brkchunk (cygwin_shared->heap_chunk_size ())
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#define assert(x)
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static unsigned page_const = 0;
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static __inline__ int
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getpagesize(void)
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{
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SYSTEM_INFO si;
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GetSystemInfo(&si);
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return (int)si.dwPageSize;
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}
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/* Initialize the heap at process start up. */
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void
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heap_init ()
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{
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/* If we're the forkee, we must allocate the heap at exactly the same place
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as our parent. If not, we don't care where it ends up. */
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page_const = getpagesize();
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if (brkbase)
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{
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DWORD chunk = brkchunk; /* allocation chunk */
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/* total size commited in parent */
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DWORD allocsize = (char *) brktop - (char *) brkbase;
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/* round up by chunk size */
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DWORD reserve_size = chunk * ((allocsize + (chunk - 1)) / chunk);
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/* Loop until we've managed to reserve an adequate amount of memory. */
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char *p;
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for (;;)
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{
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p = (char *) VirtualAlloc (brkbase, reserve_size,
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MEM_RESERVE, PAGE_READWRITE);
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if (p)
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break;
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if ((reserve_size -= page_const) <= allocsize)
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break;
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}
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if (p == NULL)
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api_fatal ("1. unable to allocate heap, heap_chunk_size %d, pid %d, %E",
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brkchunk, myself->pid);
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if (p != brkbase)
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api_fatal ("heap allocated but not at %p", brkbase);
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if (! VirtualAlloc (brkbase, allocsize, MEM_COMMIT, PAGE_READWRITE))
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api_fatal ("MEM_COMMIT failed, %E");
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}
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else
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{
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/* Initialize page mask and default heap size. Preallocate a heap
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* to assure contiguous memory. */
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brk = brktop = brkbase = VirtualAlloc(NULL, brkchunk, MEM_RESERVE, PAGE_NOACCESS);
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if (brkbase == NULL)
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api_fatal ("2. unable to allocate heap, heap_chunk_size %d, %E",
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brkchunk);
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}
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page_const--;
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malloc_init ();
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}
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#define pround(n) (((size_t)(n) + page_const) & ~page_const)
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/* FIXME: This function no longer handles "split heaps". */
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extern "C" void *
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_sbrk(int n)
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{
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char *newtop, *newbrk;
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unsigned commitbytes, newbrksize;
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if (n == 0)
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return brk; /* Just wanted to find current brk address */
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newbrk = (char *) brk + n; /* Where new brk will be */
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newtop = (char *) pround (newbrk); /* Actual top of allocated memory -
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on page boundary */
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if (newtop == brktop)
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goto good;
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if (n < 0)
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{ /* Freeing memory */
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assert(newtop < brktop);
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n = (char *) brktop - newtop;
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if (VirtualFree(newtop, n, MEM_DECOMMIT)) /* Give it back to OS */
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goto good; /* Didn't take */
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else
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goto err;
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}
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assert(newtop > brktop);
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/* Need to grab more pages from the OS. If this fails it may be because
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* we have used up previously reserved memory. Or, we're just plumb out
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* of memory. */
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commitbytes = pround (newtop - (char *) brktop);
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if (VirtualAlloc(brktop, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL)
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goto good;
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/* Couldn't allocate memory. Maybe we can reserve some more.
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Reserve either the maximum of the standard brkchunk or the requested
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amount. Then attempt to actually allocate it. */
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if ((newbrksize = brkchunk) < commitbytes)
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newbrksize = commitbytes;
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if ((VirtualAlloc(brktop, newbrksize, MEM_RESERVE, PAGE_NOACCESS) != NULL) &&
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(VirtualAlloc(brktop, commitbytes, MEM_COMMIT, PAGE_READWRITE) != NULL))
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goto good;
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err:
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set_errno (ENOMEM);
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return (void *) -1;
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good:
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void *oldbrk = brk;
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brk = newbrk;
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brktop = newtop;
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return oldbrk;
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}
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