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102 lines
3.7 KiB
C
102 lines
3.7 KiB
C
/*
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* Stack-less Just-In-Time compiler
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*
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* Copyright Zoltan Herczeg (hzmester@freemail.hu). All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without modification, are
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* permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this list of
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* conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice, this list
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* of conditions and the following disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) AND CONTRIBUTORS ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
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* SHALL THE COPYRIGHT HOLDER(S) OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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This file contains a simple W^X executable memory allocator
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In *NIX, MAP_ANON is required (that is considered a feature) so make
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sure to set the right availability macros for your system or the code
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will fail to build.
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If your system doesn't support mapping of anonymous pages (ex: IRIX) it
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is also likely that it doesn't need this allocator and should be using
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the standard one instead.
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It allocates a separate map for each code block and may waste a lot of
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memory, because whatever was requested, will be rounded up to the page
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size (minimum 4KB, but could be even bigger).
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It changes the page permissions (RW <-> RX) as needed and therefore, if you
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will be updating the code after it has been generated, need to make sure to
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block any concurrent execution, or could result in a SIGBUS, that could
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even manifest itself at a different address than the one that was being
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modified.
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Only use if you are unable to use the regular allocator because of security
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restrictions and adding exceptions to your application or the system are
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not possible.
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*/
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#define SLJIT_UPDATE_WX_FLAGS(from, to, enable_exec) \
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sljit_update_wx_flags((from), (to), (enable_exec))
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SLJIT_API_FUNC_ATTRIBUTE void* sljit_malloc_exec(sljit_uw size)
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{
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sljit_uw *ptr;
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size += sizeof(sljit_uw);
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ptr = (sljit_uw*)VirtualAlloc(NULL, size,
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MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
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if (!ptr)
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return NULL;
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*ptr++ = size;
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return ptr;
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}
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SLJIT_API_FUNC_ATTRIBUTE void sljit_free_exec(void* ptr)
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{
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sljit_uw start = (sljit_uw)ptr - sizeof(sljit_uw);
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#if defined(SLJIT_DEBUG) && SLJIT_DEBUG
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sljit_uw page_mask = (sljit_uw)get_page_alignment();
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SLJIT_ASSERT(!(start & page_mask));
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#endif
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VirtualFree((void*)start, 0, MEM_RELEASE);
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}
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static void sljit_update_wx_flags(void *from, void *to, sljit_s32 enable_exec)
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{
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DWORD oldprot;
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sljit_uw page_mask = (sljit_uw)get_page_alignment();
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sljit_uw start = (sljit_uw)from;
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sljit_uw end = (sljit_uw)to;
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DWORD prot = enable_exec ? PAGE_EXECUTE : PAGE_READWRITE;
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SLJIT_ASSERT(start < end);
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start &= ~page_mask;
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end = (end + page_mask) & ~page_mask;
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VirtualProtect((void*)start, end - start, prot, &oldprot);
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}
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SLJIT_API_FUNC_ATTRIBUTE void sljit_free_unused_memory_exec(void)
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{
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/* This allocator does not keep unused memory for future allocations. */
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}
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