chromium/base/allocator/partition_allocator/src/partition_alloc/page_allocator_internals_posix.cc

// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <stdint.h>
#include <sys/mman.h>

#include "partition_alloc/build_config.h"
#include "partition_alloc/buildflags.h"
#include "partition_alloc/page_allocator.h"

#if PA_BUILDFLAG(HAS_MEMORY_TAGGING) || \
    (defined(__ARM_FEATURE_BTI_DEFAULT) && (__ARM_FEATURE_BTI_DEFAULT == 1))
struct __ifunc_arg_t;

#include "partition_alloc/aarch64_support.h"

#define NEEDS_HANDLING_OF_HW_CAPABILITIES
#endif

// PA_PROT_BTI requests a page that supports BTI landing pads.
#define PA_PROT_BTI …

// PA_PROT_MTE requests a page that's suitable for memory tagging.
#define PA_PROT_MTE …

namespace partition_alloc::internal {
namespace {

int GetAccessFlags(PageAccessibilityConfiguration accessibility,
                   bool mte_enabled,
                   bool bti_enabled) { … }

template <bool MteEnabled, bool BtiEnabled>
int GetAccessFlags(PageAccessibilityConfiguration accessibility) { … }

}  // namespace

#if defined(NEEDS_HANDLING_OF_HW_CAPABILITIES)
using GetAccessFlagsInternalFn = int(PageAccessibilityConfiguration);

extern "C" GetAccessFlagsInternalFn* ResolveGetAccessFlags(
    uint64_t hwcap,
    struct __ifunc_arg_t* hw) {
  if (IsMteEnabled(hwcap, hw)) {
    if (IsBtiEnabled(hwcap, hw)) {
      return GetAccessFlags<true, true>;
    } else {
      return GetAccessFlags<true, false>;
    }
  } else {
    if (IsBtiEnabled(hwcap, hw)) {
      return GetAccessFlags<false, true>;
    } else {
      return GetAccessFlags<false, false>;
    }
  }
}
#endif

// Resolve the implementation for GetAccessFlags using an iFunc.
int GetAccessFlags(PageAccessibilityConfiguration accessibility)
#if defined(NEEDS_HANDLING_OF_HW_CAPABILITIES)
    __attribute__((ifunc("ResolveGetAccessFlags")));
#else
{ … }
#endif

}  // namespace partition_alloc::internal