MEMORY_BASIC_INFORMATION

The MEMORY_BASIC_INFORMATION structure contains information about a range of pages in the virtual address space of a process. The VirtualQuery and VirtualQueryEx functions use this structure.

typedef struct _MEMORY_BASIC_INFORMATION { // mbi

PVOID BaseAddress; // base address of region

PVOID AllocationBase; // allocation base address

DWORD AllocationProtect; // initial access protection

DWORD RegionSize; // size, in bytes, of region

DWORD State; // committed, reserved, free

DWORD Protect; // current access protection

DWORD Type; // type of pages

} MEMORY_BASIC_INFORMATION;

typedef MEMORY_BASIC_INFORMATION *PMEMORY_BASIC_INFORMATION;

Members

BaseAddress

Points to the base address of the region of pages.

AllocationBase

Points to the base address of a range of pages allocated by the VirtualAlloc function. The page pointed to by the BaseAddress member is contained within this allocation range.

AllocationProtect

Specifies the access protection given when the region was initially allocated. One of the following flags can be present, along with the PAGE_GUARD and PAGE_NOCACHE protection modifier flags:

Flag	Meaning
PAGE_READONLY	Enables read access to the committed region of pages. An attempt to write to the committed region results in an access violation. If the system differentiates between read-only access and execute access, an attempt to execute code in the committed region results in an access violation.
PAGE_READWRITE	Enables both read and write access to the committed region of pages.
PAGE_WRITECOPY	Gives copy-on-write access to the committed region of pages.
PAGE_EXECUTE	Enables execute access to the committed region of pages. An attempt to read or write to the committed region results in an access violation.
PAGE_EXECUTE_READ	Enables execute and read access to the committed region of pages. An attempt to write to the committed region results in an access violation.
PAGE_EXECUTE_READWRITE	Enables execute, read, and write access to the committed region of pages.
PAGE_EXECUTE_WRITECOPY	Enables execute, read, and write access to the committed region of pages. The pages are shared read-on-write and copy-on-write.
PAGE_GUARD	Protects the page with the underlying page protection. However, access to the region causes a "guard page entered" condition to be raised in the subject process. This flag is a page protection modifier, only valid when used with one of the page protections other than PAGE_NOACCESS.
PAGE_NOACCESS	Disables all access to the committed region of pages. An attempt to read from, write to, or execute in the committed region results in an access violation exception, called a general protection (GP) fault.
PAGE_NOCACHE	Allows no caching of the committed regions of pages. The hardware attributes for the physical memory should be set to no cache. This is not recommended for general usage. It is useful for device drivers; for example, mapping a video frame buffer with no caching. This flag is a page protection modifier, only valid when used with one of the page protections other than PAGE_NOACCESS.

RegionSize

Specifies the size, in bytes, of the region beginning at the base address in which all pages have identical attributes.

State

Specifies the state of the pages in the region. One of the following states is indicated:

State	Meaning
MEM_COMMIT	Indicates committed pages for which physical storage has been allocated, either in memory or in the paging file on disk.
MEM_FREE	Indicates free pages not accessible to the calling process and available to be allocated. For free pages, the information in the AllocationBase, AllocationProtect, Protect, and Type members is undefined.
MEM_RESERVE	Indicates reserved pages where a range of the process's virtual address space is reserved without allocating any physical storage. For reserved pages, the information in the Protect member is undefined.

Protect

Specifies the access protection of the pages in the region. One of the flags listed for the AllocationProtect member is specified.

Type

Specifies the type of pages in the region. The following types are defined:

Type	Meaning
MEM_IMAGE	Indicates that the memory pages within the region are mapped into the view of an image section.
MEM_MAPPED	Indicates that the memory pages within the region are mapped into the view of a section.
MEM_PRIVATE	Indicates that the memory pages within the region are private (not shared by other processes).

See Also

VirtualAlloc, VirtualQuery, VirtualQueryEx

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