55a7ad2d58
The various Pals were given different meanings in CHECK_CLIENT and non-CHECK_CLIENT builds. This was because it is essential that in the CHECK_CLIENT builds access is prevented, when not requested. This PR separates the CHECK_CLIENT concept from how the Pal should be implemented.
50 lines
1.3 KiB
C++
50 lines
1.3 KiB
C++
#pragma once
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#include "pal_posix.h"
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#include <sys/mman.h>
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namespace snmalloc
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{
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/**
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* Generic *BSD PAL mixin. This provides features that are common to the BSD
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* family.
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*/
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template<typename OS>
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class PALBSD : public PALPOSIX<OS>
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{
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public:
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/**
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* Bitmap of PalFeatures flags indicating the optional features that this
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* PAL supports.
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*
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* The generic BSD PAL does not add any features that are not supported by
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* generic POSIX systems, but explicitly declares this variable to remind
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* anyone who extends this class that they may need to modify this field.
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*/
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static constexpr uint64_t pal_features = PALPOSIX<OS>::pal_features;
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/**
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* Notify platform that we will not be using these pages.
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*
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* BSD systems provide the `MADV_FREE` flag to `madvise`, which allows the
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* operating system to replace the pages with CoW copies of a zero page at
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* any point between the call and the next write to that page.
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*/
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static void notify_not_using(void* p, size_t size) noexcept
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{
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SNMALLOC_ASSERT(is_aligned_block<OS::page_size>(p, size));
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#if !defined(NDEBUG)
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memset(p, 0x5a, size);
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#endif
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madvise(p, size, MADV_FREE);
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if constexpr (PalEnforceAccess)
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{
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mprotect(p, size, PROT_NONE);
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}
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}
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};
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} // namespace snmalloc
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