From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <4730A96C.7050601@free.fr>
Date: Tue,  6 Nov 2007 18:50:36 +0100
From: Philippe Anel <xigh@free.fr>
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To: Fans of the OS Plan 9 from Bell Labs <9fans@cse.psu.edu>
Subject: Re: [9fans] Memory management questions/not plan-9 specific
References: <11F071B3-1B01-4272-9EA4-1C2BD50BCC0B@telus.net>
	<4730A5CD.6050607@free.fr>
In-Reply-To: <4730A5CD.6050607@free.fr>
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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 =3D=3D EXCEPTION_ACCESS_VIOLATION) {
        if(ep->ExceptionRecord->ExceptionInformation[1] =3D=3D (DWORD_PTR=
)=20
Page){
            Page =3D VirtualAlloc(Page, 4096, MEM_COMMIT, PAGE_READWRITE)=
;
            if(Page =3D=3D 0)
                sysfatal("VirtualAlloc: commit");
            return EXCEPTION_CONTINUE_EXECUTION;
        }
        return EXCEPTION_EXECUTE_HANDLER;
    }
    return EXCEPTION_CONTINUE_SEARCH;
}

int main(int argc, char ** argv)
{
    // Reserve
    Page =3D VirtualAlloc(0, 4096, MEM_RESERVE, PAGE_READWRITE);
    if(Page =3D=3D 0)
        sysfatal("VirtualAlloc: reserve");
    __try{
        // Touch
        *Page =3D 0;
        puts("touched.");
    }
    __except(filter(GetExceptionCode(), GetExceptionInformation()))
    {
        puts("in except");
    }
    return 0;
}


Philippe Anel a =E9crit :
> l4 (http://en.wikipedia.org/wiki/L4_microkernel_family) has such api=20
> ... but it is only a kernel.
>
> Paul Lalonde a =E9crit :
>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1
>>
>> I have an application I'm building which requires OS support to allow=20
>> a user-space function to fill a page on page-faults.  Ideally, I=20
>> could reserve a chunk of address space but not back it with memory,=20
>> and then on fault my handler would serve out data from some small=20
>> cache of user-managed physical pages.
>>
>> My google-fu has been weak in finding such a system-level API in any=20
>> OS.  Has this got a name I should be searching on?  I can't believe=20
>> no-one has implemented user-level page replacement.
>>
>> Thanks,
>>    Paul
>>
>> -----BEGIN PGP SIGNATURE-----
>> Version: GnuPG v1.4.3 (Darwin)
>>
>> iD8DBQFHMKM4pJeHo/Fbu1wRAgezAKCSDVI812jisKkliXjpsWTMU3AlogCcDkOl
>> liIiMj9Y/2xwHx1iFKjSZ8w=3D
>> =3DCAPO
>> -----END PGP SIGNATURE-----
>>
>>
>
>
>