PageAccessControl Class Reference

Using the underlying. More...

Collaboration diagram for PageAccessControl:

Public Types
typedef std::vector< Entry >	protected_t
	the list of protected pages More...
typedef protected_t::const_iterator	const_iterator

Public Member Functions
	PageAccessControl (size_t reservedSize=65535)
	PageAccessControl (procmaps &pmaps, size_t reservedSize=65535)
template<typename T >
bool	protectPage (T *addr, int prot)
	protect the page containing addr, record the amount of memory we protected NOTE To avoid SEGV, if PROT_WRITE is requested the remainder of the page containing the object at addr will be leaked with malloc before being write-locked More...
template<typename T >
bool	forbidPage (const T *addr)
	forbid access to the page containing addr, setting its prot to PROT_NONE More...
bool	forbidPage (const void *addr, size_t objSize)
	forbid access to the page containing addr, setting its prot to PROT_NONE More...
bool	forbidPage (const void *addr)
	FIXME this will not work well for objects spanning across pages. More...
bool	protectPage (const void *addr, size_t objSize, int prot)
	void* version of protectPage. Used to implement all others More...
bool	restorePageProt (const void *addr)
void	sort ()
const protected_t &	protectedPtrs () const
const_iterator	beginProtectedPtrs () const
const_iterator	endProtectedPtrs () const
void	reset ()
bool	accessed (const void *address) const
	was the page containing address accessed? More...

Private Attributes
procmaps	m_pmaps
	the content of /proc/self/maps More...
protected_t	m_protected
bool	m_protectedIsSorted

Detailed Description

Using the underlying.

access to page containing address

Member Typedef Documentation

const_iterator

typedef protected_t::const_iterator PageAccessControl::const_iterator

Definition at line 92 of file PageAccessControl.h.

protected_t

typedef std::vector<Entry> PageAccessControl::protected_t

the list of protected pages

Definition at line 91 of file PageAccessControl.h.

Constructor & Destructor Documentation

PageAccessControl() [1/2]

PageAccessControl::PageAccessControl ( size_t  reservedSize = 65535 )

inline

Definition at line 29 of file PageAccessControl.h.

                                               :
    m_pmaps(),
    m_protectedIsSorted(false)
  {
    //we must reserve enough elements, or we risk vector allocating in a protected page during handle()...
    m_protected.reserve(reservedSize);
  }

PageAccessControl() [2/2]

PageAccessControl::PageAccessControl ( procmaps &  pmaps, size_t  reservedSize = 65535  )

inline

Definition at line 36 of file PageAccessControl.h.

                                                                :
    m_pmaps(pmaps),
    m_protectedIsSorted(false)
  {
    //we must reserve enough elements, or we risk vector allocating in a protected page during handle()...
    m_protected.reserve(reservedSize);
  }

Member Function Documentation

accessed()

bool PageAccessControl::accessed

(

const void *

address

)

const

was the page containing address accessed?

Definition at line 118 of file PageAccessControl.cxx.

                                                          {
  bool acc(false);
  //fixme: poor man implementation
  Entry eaxx(address,0,0,0);
  PageAccessControl::const_iterator ia(beginProtectedPtrs()),
    ea(endProtectedPtrs());
  while (!acc && ia != ea) {
    //    std::cout << address << "page addr " << eaxx.addr << " ia " << ia->addr << " res " << ia->restored << std::endl;
    acc = (eaxx.addr == ia->addr && 0 != ia->restored);
    ++ia;
  }
  return acc;
}

beginProtectedPtrs()

const_iterator PageAccessControl::beginProtectedPtrs ( ) const

inline

Definition at line 94 of file PageAccessControl.h.

{ return m_protected.begin(); }

endProtectedPtrs()

const_iterator PageAccessControl::endProtectedPtrs ( ) const

inline

Definition at line 95 of file PageAccessControl.h.

{ return m_protected.end(); }

forbidPage() [1/3]

template<typename T >

bool PageAccessControl::forbidPage ( const T *  addr )

inline

forbid access to the page containing addr, setting its prot to PROT_NONE

Definition at line 55 of file PageAccessControl.h.

                                 {
    return forbidPage(addr, sizeof(T));
  }

forbidPage() [2/3]

bool PageAccessControl::forbidPage ( const void *  addr )

inline

FIXME this will not work well for objects spanning across pages.

Definition at line 65 of file PageAccessControl.h.

                                    {
    return protectPage(addr, 4, PROT_NONE);
  }

forbidPage() [3/3]

bool PageAccessControl::forbidPage ( const void *  addr, size_t  objSize  )

inline

forbid access to the page containing addr, setting its prot to PROT_NONE

Definition at line 60 of file PageAccessControl.h.

                                                    {
    return protectPage(addr, objSize, PROT_NONE);
  }

protectedPtrs()

const protected_t& PageAccessControl::protectedPtrs ( ) const

inline

Definition at line 93 of file PageAccessControl.h.

{ return m_protected; }

protectPage() [1/2]

bool PageAccessControl::protectPage	(	const void *	addr,
		size_t	objSize,
		int	prot
	)

void* version of protectPage. Used to implement all others

Definition at line 56 of file PageAccessControl.cxx.

                                                                         {
  int  rc(-1);
  const procmaps::Entry *e=m_pmaps.getEntry(addr,true);
  //this is the length of the range we are going to protect
  if (0 != e) {
    const void *pageAddr = page_address(addr);
    size_t lenProt = (size_t)addr - (size_t)(pageAddr) + objSize;
    size_t nextProt = (size_t)addr + objSize;
    size_t nextUnprot = (size_t)(next_page_address((void*)(nextProt-1)));
    int pageProt(PROT_NONE);
    if (e->readable) pageProt |= PROT_READ;
    if (e->writable) pageProt |= PROT_WRITE;
    if (e->executable) pageProt |= PROT_EXEC;
    if (pageProt != prot) {
      //fill up the space from nextProt to nextUnprot to avoid allocations
      //in the locked pages, and SEGVs...
//       void *leak(0);
//       if (0 == (prot & PROT_WRITE)) {
//  size_t lenLeak(nextUnprot-nextProt-1);
//  leak=malloc(lenLeak);
//  if ((size_t)leak<nextUnprot && (size_t)leak + lenLeak>=nextUnprot) {
//    //we do not want to allocate our buffer memory past the current
//    //page, so trim it down
//    free(leak);
//    lenLeak=nextUnprot - (size_t)leak -1;
//    leak=malloc(lenLeak);
//  } 
//  if (leak < pageAddr ||
//      (size_t)leak >= nextUnprot) {
//    //leak has been allocated into previous/next page
//    //better get rid of it as it will likely
//    //be locked by another protectPage
//    free(leak);
//    leak=0; 
//  } else {
// #ifdef DEBUG
//    printf("PageAccessControl::protectPage DEBUG: fill up space from %p to 0x%x to avoid allocations in locked pages\n",
//       leak, (int)leak+lenLeak);
// #endif
//  }
//       }
 
      void* pageAddr_nc ATLAS_THREAD_SAFE = const_cast<void*> (pageAddr);
      if (0 == (rc = mprotect( pageAddr_nc,
                   lenProt,
                   prot))) {
    m_protected.push_back(Entry(pageAddr,lenProt, pageProt, 0));
    m_protectedIsSorted=false; //FIXME we should use a mapvector
#ifdef DEBUG
    printf("PageAccessControl::protectPage DEBUG: set protection %i for page range %p - 0x%lx containing address range=%p - 0x%lx\n",
           prot,
           pageAddr, 
           (long unsigned int)(nextUnprot - 1), 
           addr,
           (long unsigned int)(nextProt -1) );
#endif
      }
    } else rc=0;
  } else printf("PageAccessControl::protectPage WARNING: no entry in procmap for addr=%p, page protection not restored \n",addr);
  return (rc == 0);
}

protectPage() [2/2]

template<typename T >

bool PageAccessControl::protectPage ( T *  addr, int  prot  )

inline

protect the page containing addr, record the amount of memory we protected NOTE To avoid SEGV, if PROT_WRITE is requested the remainder of the page containing the object at addr will be leaked with malloc before being write-locked

Definition at line 49 of file PageAccessControl.h.

                                      {
    return protectPage(addr, sizeof(T), prot);
  }

reset()

void PageAccessControl::reset ( )

inline

Definition at line 96 of file PageAccessControl.h.

{ m_protected.clear(); }

restorePageProt()

bool PageAccessControl::restorePageProt

(

const void *

addr

)

Definition at line 27 of file PageAccessControl.cxx.

                                                    {
  int rc(-1);
  sort();
  Entry ea(addr,0,0,0);
  protected_t::iterator entry=
    std::lower_bound(m_protected.begin(), m_protected.end(), ea);
  if (entry != m_protected.end() &&
      entry->addr == ea.addr) {
    //found it. Restore page prot
    const void* pageAddr = page_address(entry->addr);
    void* pageAddr_nc ATLAS_THREAD_SAFE = const_cast<void*> (pageAddr);
    rc=mprotect( pageAddr_nc, entry->lenProt, entry->prot);
    if (rc==0) {
#ifdef DEBUG
      printf("PageAccessControl::restorePageProt DEBUG: restored protection %i for page %p containing address %p \n",
         entry->prot,
         page_address(entry->addr), 
         entry->addr);
      printf(" FIXME NOT Freeing memory at %p \n", entry->leak );
#endif
      //      free(entry->leak);
      entry->leak=0;
      ++(entry->restored);
    }
  } else printf("WARNING no entry in procmap for addr=%p, page protection not restored \n",addr);
  return (rc == 0);
}

sort()

void PageAccessControl::sort

(

)

Definition at line 20 of file PageAccessControl.cxx.

                        {
  if (!m_protectedIsSorted) {
    std::sort(m_protected.begin(), m_protected.end());
    m_protectedIsSorted=true;
  }
}

Member Data Documentation

m_pmaps

procmaps PageAccessControl::m_pmaps

private

the content of /proc/self/maps

Definition at line 104 of file PageAccessControl.h.

m_protected

protected_t PageAccessControl::m_protected

private

Definition at line 109 of file PageAccessControl.h.

m_protectedIsSorted

bool PageAccessControl::m_protectedIsSorted

private

Definition at line 110 of file PageAccessControl.h.

---

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

• PageAccessControlSvc.h
• PageAccessControl.h
• PageAccessControl.cxx