Allocation dynamique de mémoire en asm

Bonjour,
Comme vous l'avez vu dans le sujet, j'aurais voulu savoir s'il était possible d'affecter dynamiquement de la mémoire en assembleur ?
Peut-être existe-t-il une interruption système qui le permet ou ....
merci...

dépendant de l'os spécifie pour quel os dans ta question.

Blustuff.

Dans un premier temps se serait pour windows 95.
Pour linux j'ai vu qu'il y avait la librairie libasm, mais je ne comprend pas tout (et en plus je n'ai pas pris le temps ce qui n'arrange rien :c)

Ou est-ce que je pourrais trouver de la doc sur la gestion de la mémoire en asm dans un environnment avec OS (ie avec gestion des processus et donc allocation de la mémoire par l'Os)

Sinon, si je lance directement à partir du bios, je ne pense pas avoir besoin d'allocation de mémoire vu que j'y accède directement sans contrôle ?? vrai ???

merci pour tout :c)

Sous DOS on utilise 48h et 4Ah de l'interruption 21h...

Pour windows, il faut appeller la fonction GlobalAlloc :

Citation:

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The GlobalAlloc function allocates the specified number of bytes from the heap. In the linear Win32 API environment, there is no difference between the local heap and the global heap.

HGLOBAL GlobalAlloc(

UINT uFlags, // object allocation attributes
DWORD dwBytes // number of bytes to allocate
);


Parameters

uFlags

Specifies how to allocate memory. If zero is specified, the default is GMEM_FIXED. Except for the incompatible combinations that are specifically noted, any combination of the following flags can be used. To indicate whether the function allocates fixed or movable memory, specify one of the first four flags:

Flag Meaning
GMEM_FIXED Allocates fixed memory. This flag cannot be combined with the GMEM_MOVEABLE or GMEM_DISCARDABLE flag. The return value is a pointer to the memory block. To access the memory, the calling process simply casts the return value to a pointer.
GMEM_MOVEABLE Allocates movable memory. This flag cannot be combined with the GMEM_FIXED flag. The return value is the handle of the memory object. The handle is a 32-bit quantity that is private to the calling process. To translate the handle into a pointer, use the GlobalLock function.
GPTR Combines the GMEM_FIXED and GMEM_ZEROINIT flags.
GHND Combines the GMEM_MOVEABLE and GMEM_ZEROINIT flags.
GMEM_DDESHARE Allocates memory to be used by the dynamic data exchange (DDE) functions for a DDE conversation. Unlike Windows version 3. x, this memory is not shared globally. However, this flag is available for compatibility purposes. It may be used by some applications to enhance the performance of DDE operations and should, therefore, be specified if the memory is to be used for DDE. Only processes that use DDE or the clipboard for interprocess communications should specify this flag.
GMEM_DISCARDABLE Allocates discardable memory. This flag cannot be combined with the GMEM_FIXED flag. Some Win32-based applications may ignore this flag.
GMEM_LOWER Ignored. This flag is provided only for compatibility with Windows version 3. x.
GMEM_NOCOMPACT Does not compact or discard memory to satisfy the allocation request.
GMEM_NODISCARD Does not discard memory to satisfy the allocation request.
GMEM_NOT_BANKED Ignored. This flag is provided only for compatibility with Windows version 3. x.
GMEM_NOTIFY Ignored. This flag is provided only for compatibility with Windows version 3. x.
GMEM_SHARE Same as the GMEM_DDESHARE flag.
GMEM_ZEROINIT Initializes memory contents to zero.


dwBytes

Specifies the number of bytes to allocate. If this parameter is zero and the uFlags parameter specifies the GMEM_MOVEABLE flag, the function returns a handle to a memory object that is marked as discarded.



Return Values

If the function succeeds, the return value is the handle of the newly allocated memory object.
If the function fails, the return value is NULL. To get extended error information, call GetLastError.

Remarks

If the heap does not contain sufficient free space to satisfy the request, GlobalAlloc returns NULL.
Because NULL is used to indicate an error, virtual address zero is never allocated. It is, therefore, easy to detect the use of a NULL pointer.
All memory is created with execute access; no special function is required to execute dynamically generated code.
Memory allocated with this function is guaranteed to be aligned on an 8-byte boundary.
The GlobalAlloc and LocalAlloc functions are limited to a combined total of 65,536 handles for GMEM_MOVEABLE and LMEM_MOVEABLE memory per process. This limitation does not apply to GMEM_FIXED or LMEM_FIXED memory.

If this function succeeds, it allocates at least the amount of memory requested. If the actual amount allocated is greater than the amount requested, the process can use the entire amount. To determine the actual number of bytes allocated, use the GlobalSize function.

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pour Dos Benoit t'as donné la réponse.


Blustuff.

merci beaucoup :c)
Le seul problème c'est que pour windows j'ai pas beaucoup de compétence...Il me semble que pour appeler la fonction que tu dis il faut que je fasse : invoke laFonction
c'est bien ça ?[/b]

oui en gros si tu veux appeller la fonction

Code:

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a = GlobalAlloc(GMEM_FIXED, 1000);

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tu dois faire :

Code:

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1 2 3 4 5

mov eax, 1000 push eax push GMEM_FIXED call GlobalAlloc mov a, eax

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Ce qui reviens exactement au même que

Code:

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1 2	invoke GlobalAlloc, GMEM_FIXED, 1000 mov a, eax

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sauf que pour utiliser invoke, il faut définir un prototype. JE te le donen de tête mais je suis plus très sur :

Code:

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GlobalAlloc PROTO uFlags:DOWRD, dwBytes:DWORD

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tu dois placer cette déclaration de prototype avant tout utilisation de invoke pour la fonction GloballAlloc


Blustuff.

ok, c'est noté :D merci beaucoup .....