foedus::assorted::ProtectedBoundary Struct Reference

A 4kb dummy data placed between separate memory regions so that we can check if/where a bogus memory access happens. More...

Detailed Description

A 4kb dummy data placed between separate memory regions so that we can check if/where a bogus memory access happens.

As a middleware, we often allocate a large chunk of memory and internally split it into smaller data regions. While it reduces overheads, that means a lack of memory boundary check. Instead, we place this dummy block to achieve it. When we shut down the system, we check if there happened any unexpected overrun between memory regions. In addition, we also use mprotect() to prohibit accesses to these dummy blocks, which would immediately fire up SIGSEGV for bogus access, making debugging easier.

mprotect() limit: max_map_count

mprotect() has one limitation: it could use up max_map_count. What you might observe is after around 64k mprotect() calls, it starts failing with ENOMEM. Moreover, all following memory allocations (eg mmap) also fail with ENOMEM once this starts happening. The issue goes away by increasing max_map_count : sudo sysctl -w vm.max_map_count=2147483647

Definition at line 56 of file protected_boundary.hpp.

#include <protected_boundary.hpp>

Public Types
enum	Constants { kByteSize = 1 << 12, kMaxBoundaryNameLength = 128, kWordCount = (kByteSize - kMaxBoundaryNameLength) / 8 }

Public Member Functions
ErrorCode	acquire_protect ()
	Puts a strict access prohibition via mprotect(). More...
ErrorCode	release_protect ()
	Removes all access restrictions via mprotect(). More...
void	reset (const std::string &boundary_name)
	Fills the block with magic words. More...
void	assert_boundary () const
	Called at shutdown to check whether these boundaries were not accessed. More...
std::string	get_boundary_name () const

Public Attributes
char	boundary_name_ [kMaxBoundaryNameLength]
uint64_t	data_ [kWordCount]

Member Enumeration Documentation

enum foedus::assorted::ProtectedBoundary::Constants

Enumerator
kByteSize
kMaxBoundaryNameLength
kWordCount

Definition at line 57 of file protected_boundary.hpp.

                 {
    kByteSize = 1 << 12,
    kMaxBoundaryNameLength = 128,
    kWordCount = (kByteSize - kMaxBoundaryNameLength) / 8,
  };

Member Function Documentation

ErrorCode foedus::assorted::ProtectedBoundary::acquire_protect

(

)

Puts a strict access prohibition via mprotect().

Attention

This method might cause severe performance degradation. Use in appropriate places. We use hugepages in most places, but mprotect() most likely splits the TLB entries to achieve the protection, throwing away the performance benefits of hugepages.

Note

this method is idempotent. safe to call multiple times

Returns

The only possible error is kErrorCodeOsMProtectFailed

Definition at line 25 of file protected_boundary.cpp.

References foedus::kErrorCodeOk, and foedus::kErrorCodeOsMProtectFailed.

Referenced by foedus::memory::PagePoolPimpl::initialize_once().

                                             {
  int ret = ::mprotect(this, sizeof(ProtectedBoundary), PROT_NONE);
  if (ret != 0) {
    return kErrorCodeOsMProtectFailed;
  }
  return kErrorCodeOk;
}

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void foedus::assorted::ProtectedBoundary::assert_boundary ( ) const

inline

Called at shutdown to check whether these boundaries were not accessed.

Attention

This must be invoked AFTER release_protect()

Definition at line 103 of file protected_boundary.hpp.

References ASSERT_ND, and kWordCount.

Referenced by foedus::soc::SharedMemoryRepo::deallocate_shared_memories(), and foedus::memory::PagePoolPimpl::uninitialize_once().

                                    {
    for (uint32_t i = 0; i < kWordCount; ++i) {
      ASSERT_ND(data_[i] == kProtectedBoundaryMagicWord);
    }
  }

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std::string foedus::assorted::ProtectedBoundary::get_boundary_name ( ) const

inline

Definition at line 109 of file protected_boundary.hpp.

References ASSERT_ND, and kMaxBoundaryNameLength.

Referenced by foedus::memory::PagePoolPimpl::uninitialize_once().

                                      {
    uint16_t len;
    for (len = 0; len < kMaxBoundaryNameLength; ++len) {
      if (boundary_name_[len] == 0) {
        break;
      }
    }
    ASSERT_ND(len < kMaxBoundaryNameLength);
    return std::string(boundary_name_, len);
  }

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ErrorCode foedus::assorted::ProtectedBoundary::release_protect

(

)

Removes all access restrictions via mprotect().

Attention

This method might cause severe performance hit. Use in appropriate places.

Note

this method is idempotent. safe to call multiple times

Returns

The only possible error is kErrorCodeOsMProtectFailed

Definition at line 33 of file protected_boundary.cpp.

References foedus::kErrorCodeOk, and foedus::kErrorCodeOsMProtectFailed.

Referenced by foedus::soc::SharedMemoryRepo::deallocate_shared_memories(), and foedus::memory::PagePoolPimpl::uninitialize_once().

                                             {
  int ret = ::mprotect(this, sizeof(ProtectedBoundary), PROT_READ | PROT_WRITE);
  if (ret != 0) {
    return kErrorCodeOsMProtectFailed;
  }
  return kErrorCodeOk;
}

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void foedus::assorted::ProtectedBoundary::reset ( const std::string &  boundary_name )

inline

Fills the block with magic words.

Attention

This must be invoked BEFORE acquire_protect()

Definition at line 88 of file protected_boundary.hpp.

References kMaxBoundaryNameLength, foedus::assorted::kProtectedBoundaryMagicWord, and kWordCount.

Referenced by foedus::memory::PagePoolPimpl::initialize_once().

                                                  {
    uint16_t copy_len = std::min<uint64_t>(boundary_name.length(), kMaxBoundaryNameLength);
    boundary_name.copy(boundary_name_, copy_len, 0);
    if (copy_len < kMaxBoundaryNameLength) {
      std::memset(boundary_name_ + copy_len, 0, kMaxBoundaryNameLength- copy_len);
    }
    for (uint32_t i = 0; i < kWordCount; ++i) {
      data_[i] = kProtectedBoundaryMagicWord;
    }
  }

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Member Data Documentation

char foedus::assorted::ProtectedBoundary::boundary_name_[kMaxBoundaryNameLength]

Definition at line 63 of file protected_boundary.hpp.

uint64_t foedus::assorted::ProtectedBoundary::data_[kWordCount]

Definition at line 64 of file protected_boundary.hpp.

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The documentation for this struct was generated from the following files:

• /home/shino/foedus_code/foedus-core/include/foedus/assorted/protected_boundary.hpp
• /home/shino/foedus_code/foedus-core/src/foedus/assorted/protected_boundary.cpp