Merge branch 'topic/kaslr-book3e32' into next (3df19111) · Commits · 戴 / test

Documentation/powerpc/index.rst

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		@@ -19,6 +19,7 @@ powerpc
		firmware-assisted-dump
		hvcs
		isa-versions
		kaslr-booke32
		mpc52xx
		pci_iov_resource_on_powernv
		pmu-ebb

Documentation/powerpc/kaslr-booke32.rst

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		.. SPDX-License-Identifier: GPL-2.0

		===========================
		KASLR for Freescale BookE32
		===========================

		The word KASLR stands for Kernel Address Space Layout Randomization.

		This document tries to explain the implementation of the KASLR for
		Freescale BookE32. KASLR is a security feature that deters exploit
		attempts relying on knowledge of the location of kernel internals.

		Since CONFIG_RELOCATABLE has already supported, what we need to do is
		map or copy kernel to a proper place and relocate. Freescale Book-E
		parts expect lowmem to be mapped by fixed TLB entries(TLB1). The TLB1
		entries are not suitable to map the kernel directly in a randomized
		region, so we chose to copy the kernel to a proper place and restart to
		relocate.

		Entropy is derived from the banner and timer base, which will change every
		build and boot. This not so much safe so additionally the bootloader may
		pass entropy via the /chosen/kaslr-seed node in device tree.

		We will use the first 512M of the low memory to randomize the kernel
		image. The memory will be split in 64M zones. We will use the lower 8
		bit of the entropy to decide the index of the 64M zone. Then we chose a
		16K aligned offset inside the 64M zone to put the kernel in::

		KERNELBASE

		\|--> 64M <--\|
		\| \|
		+---------------+ +----------------+---------------+
		\| \|....\| \|kernel\| \| \|
		+---------------+ +----------------+---------------+
		\| \|
		\|-----> offset <-----\|

		kernstart_virt_addr

		To enable KASLR, set CONFIG_RANDOMIZE_BASE = y. If KASLR is enable and you
		want to disable it at runtime, add "nokaslr" to the kernel cmdline.

arch/powerpc/Kconfig

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		@@ -551,6 +551,17 @@ config RELOCATABLE
		setting can still be useful to bootwrappers that need to know the
		load address of the kernel (eg. u-boot/mkimage).

		config RANDOMIZE_BASE
		bool "Randomize the address of the kernel image"
		depends on (FSL_BOOKE && FLATMEM && PPC32)
		depends on RELOCATABLE
		help
		Randomizes the virtual address at which the kernel image is
		loaded, as a security feature that deters exploit attempts
		relying on knowledge of the location of kernel internals.

		If unsure, say Y.

		config RELOCATABLE_TEST
		bool "Test relocatable kernel"
		depends on (PPC64 && RELOCATABLE)

arch/powerpc/include/asm/nohash/mmu-book3e.h

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		@@ -75,7 +75,6 @@
		#define MAS2_E 0x00000001
		#define MAS2_WIMGE_MASK 0x0000001f
		#define MAS2_EPN_MASK(size) (~0 << (size + 10))
		#define MAS2_VAL(addr, size, flags) ((addr) & MAS2_EPN_MASK(size) \| (flags))

		#define MAS3_RPN 0xFFFFF000
		#define MAS3_U0 0x00000200
		@@ -221,6 +220,16 @@
		#define TLBILX_T_CLASS2 6
		#define TLBILX_T_CLASS3 7

		/*
		* The mapping only needs to be cache-coherent on SMP, except on
		* Freescale e500mc derivatives where it's also needed for coherent DMA.
		*/
		#if defined(CONFIG_SMP) \|\| defined(CONFIG_PPC_E500MC)
		#define MAS2_M_IF_NEEDED MAS2_M
		#else
		#define MAS2_M_IF_NEEDED 0
		#endif

		#ifndef __ASSEMBLY__
		#include <asm/bug.h>

arch/powerpc/include/asm/page.h

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		@@ -325,6 +325,13 @@ void arch_free_page(struct page *page, int order);

		struct vm_area_struct;

		extern unsigned long kernstart_virt_addr;

		static inline unsigned long kaslr_offset(void)
		{
		return kernstart_virt_addr - KERNELBASE;
		}

		#include <asm-generic/memory_model.h>
		#endif /* __ASSEMBLY__ */
		#include <asm/slice.h>

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