Re: [9fans] Memory management questions/not plan-9 specific

[Philippe Anel <xigh@free.fr>]

You also can do this in windows :


#include <windows.h>
#include <stdio.h>

void sysfatal(char * reason)
{
    printf("'%s' failed with error %d\n", reason, GetLastError());
    ExitProcess(0);
}

PUCHAR    Page;

int filter(unsigned int code, struct _EXCEPTION_POINTERS *ep)
{
    if (code == EXCEPTION_ACCESS_VIOLATION) {
        if(ep->ExceptionRecord->ExceptionInformation[1] == (DWORD_PTR) 
Page){
            Page = VirtualAlloc(Page, 4096, MEM_COMMIT, PAGE_READWRITE);
            if(Page == 0)
                sysfatal("VirtualAlloc: commit");
            return EXCEPTION_CONTINUE_EXECUTION;
        }
        return EXCEPTION_EXECUTE_HANDLER;
    }
    return EXCEPTION_CONTINUE_SEARCH;
}

int main(int argc, char ** argv)
{
    // Reserve
    Page = VirtualAlloc(0, 4096, MEM_RESERVE, PAGE_READWRITE);
    if(Page == 0)
        sysfatal("VirtualAlloc: reserve");
    __try{
        // Touch
        *Page = 0;
        puts("touched.");
    }
    __except(filter(GetExceptionCode(), GetExceptionInformation()))
    {
        puts("in except");
    }
    return 0;
}


Philippe Anel a écrit :
> l4 (http://en.wikipedia.org/wiki/L4_microkernel_family) has such api 
> ... but it is only a kernel.
>
> Paul Lalonde a écrit :
>> -----BEGIN PGP SIGNED MESSAGE-----
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>> I have an application I'm building which requires OS support to allow 
>> a user-space function to fill a page on page-faults.  Ideally, I 
>> could reserve a chunk of address space but not back it with memory, 
>> and then on fault my handler would serve out data from some small 
>> cache of user-managed physical pages.
>>
>> My google-fu has been weak in finding such a system-level API in any 
>> OS.  Has this got a name I should be searching on?  I can't believe 
>> no-one has implemented user-level page replacement.
>>
>> Thanks,
>>    Paul
>>
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