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@manurautela
Created October 12, 2021 04:35
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pagefault.cpp
// A short program to demonstrate dynamic memory allocation
// using a structured exception handler.
// compile with x86 vc2019 dev prompt:
// cl /nologo /W3 /D "_DEBUG" /EHsc /guard:cf /GS /MTd /Zi pagefault.cpp
#include <windows.h>
#include <tchar.h>
#include <stdio.h>
#include <stdlib.h> // For exit
#define PAGELIMIT 80 // Number of pages to ask for
LPTSTR lpNxtPage; // Address of the next page to ask for
DWORD dwPages = 0; // Count of pages gotten so far
DWORD dwPageSize; // Page size on this computer
INT PageFaultExceptionFilter(DWORD dwCode)
{
LPVOID lpvResult;
// If the exception is not a page fault, exit.
if (dwCode != EXCEPTION_ACCESS_VIOLATION)
{
_tprintf(TEXT("Exception code = %d.\n"), dwCode);
return EXCEPTION_EXECUTE_HANDLER;
}
//_tprintf(TEXT("Exception is a page fault.\n"));
// If the reserved pages are used up, exit.
if (dwPages >= PAGELIMIT)
{
_tprintf(TEXT("Exception: out of pages.\n"));
return EXCEPTION_EXECUTE_HANDLER;
}
// Otherwise, commit another page.
// DebugBreak();
lpvResult = VirtualAlloc(
(LPVOID) lpNxtPage, // Next page to commit
dwPageSize, // Page size, in bytes
MEM_COMMIT, // Allocate a committed page
PAGE_READWRITE); // Read/write access
if (lpvResult == NULL )
{
_tprintf(TEXT("VirtualAlloc failed.\n"));
return EXCEPTION_EXECUTE_HANDLER;
}
else
{
//_tprintf(TEXT("Allocating another page.\n"));
}
// Increment the page count, and advance lpNxtPage to the next page.
dwPages++;
lpNxtPage = (LPTSTR) ((PCHAR) lpNxtPage + dwPageSize);
// Continue execution where the page fault occurred.
return EXCEPTION_CONTINUE_EXECUTION;
}
VOID ErrorExit(LPTSTR lpMsg)
{
_tprintf(TEXT("Error! %s with error code of %ld.\n"),
lpMsg, GetLastError ());
exit (0);
}
VOID _tmain(VOID)
{
LPVOID lpvBase; // Base address of the test memory
LPTSTR lpPtr; // Generic character pointer
BOOL bSuccess; // Flag
DWORD i; // Generic counter
SYSTEM_INFO sSysInfo; // Useful information about the system
GetSystemInfo(&sSysInfo); // Initialize the structure.
_tprintf (TEXT("This computer has page size %d.\n"), sSysInfo.dwPageSize);
DebugBreak();
dwPageSize = sSysInfo.dwPageSize;
// Reserve pages in the virtual address space of the process.
lpvBase = VirtualAlloc(
NULL, // System selects address
PAGELIMIT*dwPageSize, // Size of allocation
MEM_RESERVE, // Allocate reserved pages
PAGE_NOACCESS); // Protection = no access
if (lpvBase == NULL )
ErrorExit(TEXT("VirtualAlloc reserve failed."));
lpPtr = lpNxtPage = (LPTSTR) lpvBase;
// Use structured exception handling when accessing the pages.
// If a page fault occurs, the exception filter is executed to
// commit another page from the reserved block of pages.
for (i=0; i < PAGELIMIT*dwPageSize; i++)
{
__try
{
// Write to memory.
lpPtr[i] = 'a';
}
// If there's a page fault, commit another page and try again.
__except ( PageFaultExceptionFilter( GetExceptionCode() ) )
{
// This code is executed only if the filter function
// is unsuccessful in committing the next page.
_tprintf (TEXT("Exiting process.\n"));
ExitProcess( GetLastError() );
}
}
// Release the block of pages when you are finished using them.
bSuccess = VirtualFree(
lpvBase, // Base address of block
0, // Bytes of committed pages
MEM_RELEASE); // Decommit the pages
_tprintf (TEXT("Release %s.\n"), bSuccess ? TEXT("succeeded") : TEXT("failed") );
}
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