99 lines
3.2 KiB
C++
99 lines
3.2 KiB
C++
// Copyright 2022 The Chromium Authors
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_ALLOCATOR_PARTITION_ALLOCATOR_PKEY_H_
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#define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PKEY_H_
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#include "base/allocator/partition_allocator/partition_alloc_buildflags.h"
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#if BUILDFLAG(ENABLE_PKEYS)
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#include "base/allocator/partition_allocator/page_allocator_constants.h"
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#include "base/allocator/partition_allocator/partition_alloc_base/component_export.h"
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#include "base/allocator/partition_allocator/partition_alloc_base/debug/debugging_buildflags.h"
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#include <cstddef>
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#include <cstdint>
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#if !BUILDFLAG(HAS_64_BIT_POINTERS)
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#error "pkey support requires 64 bit pointers"
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#endif
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#define PA_PKEY_ALIGN_SZ SystemPageSize()
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#define PA_PKEY_ALIGN_OFFSET_MASK (PA_PKEY_ALIGN_SZ - 1)
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#define PA_PKEY_ALIGN_BASE_MASK (~PA_PKEY_ALIGN_OFFSET_MASK)
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#define PA_PKEY_ALIGN alignas(PA_PKEY_ALIGN_SZ)
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#define PA_PKEY_FILL_PAGE_SZ(size) \
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((PA_PKEY_ALIGN_SZ - (size & PA_PKEY_ALIGN_OFFSET_MASK)) % PA_PKEY_ALIGN_SZ)
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// Calculate the required padding so that the last element of a page-aligned
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// array lands on a page boundary. In other words, calculate that padding so
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// that (count-1) elements are a multiple of page size.
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#define PA_PKEY_ARRAY_PAD_SZ(Type, count) \
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PA_PKEY_FILL_PAGE_SZ(sizeof(Type) * (count - 1))
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namespace partition_alloc::internal {
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constexpr int kDefaultPkey = 0;
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constexpr int kInvalidPkey = -1;
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// Check if the CPU supports pkeys.
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bool CPUHasPkeySupport();
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// A wrapper around pkey_mprotect that falls back to regular mprotect if
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// PkeySettings::enabled is false.
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[[nodiscard]] int PkeyMprotectIfEnabled(void* addr,
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size_t len,
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int prot,
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int pkey);
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// A wrapper around pkey_mprotect without fallback.
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[[nodiscard]] int PkeyMprotect(void* addr, size_t len, int prot, int pkey);
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// If we set up a pkey pool, we need to tag global variables with the pkey to
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// make them readable in case default pkey access is disabled. Called once
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// during pkey pool initialization.
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void TagGlobalsWithPkey(int pkey);
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int PkeyAlloc(int access_rights);
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void PkeyFree(int pkey);
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// Read the pkru register (the current pkey state).
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uint32_t Rdpkru();
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// Write the pkru register (the current pkey state).
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void Wrpkru(uint32_t pkru);
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struct PkeySettings {
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bool enabled = false;
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char pad_[PA_PKEY_FILL_PAGE_SZ(sizeof(enabled))] = {};
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static PkeySettings settings PA_PKEY_ALIGN PA_CONSTINIT;
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};
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#if BUILDFLAG(PA_DCHECK_IS_ON)
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class PA_COMPONENT_EXPORT(PARTITION_ALLOC) LiftPkeyRestrictionsScope {
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public:
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static constexpr uint32_t kDefaultPkeyValue = 0x55555554;
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static constexpr uint32_t kAllowAllPkeyValue = 0x0;
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LiftPkeyRestrictionsScope();
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~LiftPkeyRestrictionsScope();
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private:
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uint32_t saved_pkey_value_;
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};
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#endif // BUILDFLAG(PA_DCHECK_IS_ON)
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} // namespace partition_alloc::internal
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#else // BUILDFLAG(ENABLE_PKEYS)
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#define PA_PKEY_ALIGN
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#define PA_PKEY_FILL_PAGE_SZ(size) 0
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#define PA_PKEY_ARRAY_PAD_SZ(Type, size) 0
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#endif // BUILDFLAG(ENABLE_PKEYS)
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#endif // BASE_ALLOCATOR_PARTITION_ALLOCATOR_PKEY_H_
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