From: Jason Yan yanaijie@huawei.com
maillist inclusion category: feature feature: PowerPC64 kaslr support bugzilla: 109306 CVE: NA
Reference: https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20200330022023.3691-...
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Now we support both 32 and 64 bit KASLR for fsl booke. Add document for 64 bit part and rename kaslr-booke32.rst to kaslr-booke.rst.
Signed-off-by: Jason Yan yanaijie@huawei.com Cc: Scott Wood oss@buserror.net Cc: Diana Craciun diana.craciun@nxp.com Cc: Michael Ellerman mpe@ellerman.id.au Cc: Christophe Leroy christophe.leroy@c-s.fr Cc: Benjamin Herrenschmidt benh@kernel.crashing.org Cc: Paul Mackerras paulus@samba.org Cc: Nicholas Piggin npiggin@gmail.com Cc: Kees Cook keescook@chromium.org Signed-off-by: Cui GaoSheng cuigaosheng1@huawei.com Signed-off-by: GUO Zihua guozihua@huawei.com --- Documentation/powerpc/index.rst | 2 +- .../{kaslr-booke32.rst => kaslr-booke.rst} | 35 ++++++++++++++++--- 2 files changed, 32 insertions(+), 5 deletions(-) rename Documentation/powerpc/{kaslr-booke32.rst => kaslr-booke.rst} (59%)
diff --git a/Documentation/powerpc/index.rst b/Documentation/powerpc/index.rst index a50834798454..5eae95a56f6e 100644 --- a/Documentation/powerpc/index.rst +++ b/Documentation/powerpc/index.rst @@ -24,7 +24,7 @@ powerpc hvcs imc isa-versions - kaslr-booke32 + kaslr-booke mpc52xx papr_hcalls pci_iov_resource_on_powernv diff --git a/Documentation/powerpc/kaslr-booke32.rst b/Documentation/powerpc/kaslr-booke.rst similarity index 59% rename from Documentation/powerpc/kaslr-booke32.rst rename to Documentation/powerpc/kaslr-booke.rst index 5681c1d1b65b..a908a42c457e 100644 --- a/Documentation/powerpc/kaslr-booke32.rst +++ b/Documentation/powerpc/kaslr-booke.rst @@ -1,15 +1,18 @@ .. SPDX-License-Identifier: GPL-2.0
-=========================== -KASLR for Freescale BookE32 -=========================== +========================= +KASLR for Freescale BookE +=========================
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 +Freescale BookE. KASLR is a security feature that deters exploit attempts relying on knowledge of the location of kernel internals.
+KASLR for Freescale BookE32 +------------------------- + 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 @@ -38,5 +41,29 @@ bit of the entropy to decide the index of the 64M zone. Then we chose a
kernstart_virt_addr
+ +KASLR for Freescale BookE64 +--------------------------- + +The implementation for Freescale BookE64 is similar to BookE32. One +difference is that Freescale BookE64 set up a TLB mapping of 1G during +booting. Another difference is that ppc64 needs the kernel to be +64K-aligned. So we can randomize the kernel in this 1G mapping and make +it 64K-aligned. This can save some code to creat another TLB map at early +boot. The disadvantage is that we only have about 1G/64K = 16384 slots to +put the kernel in:: + + KERNELBASE + + 64K |--> kernel <--| + | | | + +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ + | | | |....| | | | | | | | | |....| | | + +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ + | | 1G + |-----> offset <-----| + + kernstart_virt_addr + To enable KASLR, set CONFIG_RANDOMIZE_BASE = y. If KASLR is enabled and you want to disable it at runtime, add "nokaslr" to the kernel cmdline.