

CONFIG_RANDOMIZE_BASE: Randomize the address of the kernel image

General informations

The Linux kernel configuration item CONFIG_RANDOMIZE_BASE:

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Randomizes the physical and virtual address at which the kernel image is decompressed, as a security feature that deters exploit attempts relying on knowledge of the location of kernel internals.

Entropy is generated using the RDRAND instruction if it is supported. If RDTSC is supported, it is used as well. If neither RDRAND nor RDTSC are supported, then randomness is read from the i8254 timer.

The kernel will be offset by up to RANDOMIZE_BASE_MAX_OFFSET, and aligned according to PHYSICAL_ALIGN. Since the kernel is built using 2GiB addressing, and PHYSICAL_ALGIN must be at a minimum of 2MiB, only 10 bits of entropy is theoretically possible. At best, due to page table layouts, 64-bit can use 9 bits of entropy and 32-bit uses 8 bits.

If unsure, say N.



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