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/HIGHENTROPYVA (Support 64-Bit ASLR)

  • Article

Specifies whether the executable image supports high-entropy 64-bit address space layout randomization (ASLR).

Syntax

/HIGHENTROPYVA[:NO]

Remarks

/HIGHENTROPYVA modifies the header of an executable image file (for example, a .dll or .exe file), to indicate whether ASLR can use the entire 64-bit address space. To have an effect, set the option on both the executable and all modules that it depends on. Then an operating system that supports 64-bit ASLR can rebase the executable image's segments at load time by using 64-bit randomized virtual addresses. This large address space makes it more difficult for an attacker to guess the location of a particular memory region.

By default, /HIGHENTROPYVA is enabled for 64-bit executable images. This option requires /LARGEADDRESSAWARE, which is also enabled by default for 64-bit images. /HIGHENTROPYVA isn't applicable to 32-bit executable images, where the linker ignores the option. To explicitly disable this option, use /HIGHENTROPYVA:NO.

For /HIGHENTROPYVA to have an effect at load time, /DYNAMICBASE must also be enabled. /DYNAMICBASE is enabled by default, and is required to enable ASLR in Windows Vista and later operating systems. Earlier versions of Windows ignore this flag.

To set this linker option in Visual Studio

  1. Open the project Property Pages dialog box. For more information, see Set C++ compiler and build properties in Visual Studio.

  2. Select the Configuration Properties > Linker > Command Line property page.

  3. In Additional Options, enter /HIGHENTROPYVA or /HIGHENTROPYVA:NO.

See also