uvm.cpp

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/* Copyright (c) 2011 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include "precompiled.h"
#include "lib/sysdep/vm.h"

#include "lib/alignment.h"

// "anonymous" effectively means mapping /dev/zero, but is more efficient.
// MAP_ANONYMOUS is not in SUSv3, but is a very common extension.
// unfortunately, MacOS X only defines MAP_ANON, which Solaris says is
// deprecated. workaround there: define MAP_ANONYMOUS in terms of MAP_ANON.
#ifndef MAP_ANONYMOUS
# define MAP_ANONYMOUS MAP_ANON
#endif

static const int mmap_flags = MAP_PRIVATE|MAP_ANONYMOUS;

namespace vm {

void* ReserveAddressSpace(size_t size, size_t UNUSED(commitSize), PageType UNUSED(pageType), int UNUSED(prot))
{
    errno = 0;
    void* p = mmap(0, size, PROT_NONE, mmap_flags|MAP_NORESERVE, -1, 0);
    if(p == MAP_FAILED)
        return 0;
    return p;
}

void ReleaseAddressSpace(void* p, size_t size)
{
    ENSURE(size != 0);

    errno = 0;
    if(munmap(p, size) != 0)
        DEBUG_WARN_ERR(StatusFromErrno());
}


bool Commit(uintptr_t address, size_t size, PageType UNUSED(pageType), int prot)
{
    if(prot == PROT_NONE)   // would be understood as a request to decommit
    {
        DEBUG_WARN_ERR(ERR::INVALID_PARAM);
        return false;
    }

    errno = 0;
    if(mmap((void*)address, size, prot, mmap_flags|MAP_FIXED, -1, 0) == MAP_FAILED)
        return false;

    if(prot != (PROT_READ|PROT_WRITE))
        (void)Protect(address, size, prot);

    return true;
}

bool Decommit(uintptr_t address, size_t size)
{
    errno = 0;
    if(mmap((void*)address, size, PROT_NONE, mmap_flags|MAP_NORESERVE|MAP_FIXED, -1, 0) == MAP_FAILED)
        return false;
    return true;
}


bool Protect(uintptr_t address, size_t size, int prot)
{
    errno = 0;
    if(mprotect((void*)address, size, prot) != 0)
    {
        DEBUG_WARN_ERR(ERR::FAIL);
        return false;
    }
    return true;
}


void* Allocate(size_t size, PageType pageType, int prot)
{
    void* p = ReserveAddressSpace(size);
    if(!p)
        return 0;

    if(!Commit(uintptr_t(p), size, pageType, prot))
    {
        ReleaseAddressSpace(p, size);
        return 0;
    }

    return p;
}

void Free(void* p, size_t size)
{
    // (only the Windows implementation distinguishes between Free and ReleaseAddressSpace)
    vm::ReleaseAddressSpace(p, size);
}


void BeginOnDemandCommits()
{
    // not yet implemented, but possible with a signal handler
}

void EndOnDemandCommits()
{
    // not yet implemented, but possible with a signal handler
}


void DumpStatistics()
{
    // we haven't collected any statistics
}

}   // namespace vm