1 .. SPDX-License-Identifier: GPL-2.0
2
3 ===========================
4 KASLR for Freescale BookE32
5 ===========================
6
7 The word KASLR stands for Kernel Address Space
8
9 This document tries to explain the implementat
10 Freescale BookE32. KASLR is a security feature
11 attempts relying on knowledge of the location
12
13 Since CONFIG_RELOCATABLE has already supported
14 map or copy kernel to a proper place and reloc
15 parts expect lowmem to be mapped by fixed TLB
16 entries are not suitable to map the kernel dir
17 region, so we chose to copy the kernel to a pr
18 relocate.
19
20 Entropy is derived from the banner and timer b
21 build and boot. This not so much safe so addit
22 pass entropy via the /chosen/kaslr-seed node i
23
24 We will use the first 512M of the low memory t
25 image. The memory will be split in 64M zones.
26 bit of the entropy to decide the index of the
27 16K aligned offset inside the 64M zone to put
28
29 KERNELBASE
30
31 |--> 64M <--|
32 | |
33 +---------------+ +----------------
34 | |....| |kernel|
35 +---------------+ +----------------
36 | |
37 |-----> offset <-----|
38
39 kernstart_virt_a
40
41 To enable KASLR, set CONFIG_RANDOMIZE_BASE = y
42 want to disable it at runtime, add "nokaslr" t
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