From: Jason Yan <yanaijie@huawei.com> To: <mpe@ellerman.id.au>, <linuxppc-dev@lists.ozlabs.org>, <diana.craciun@nxp.com>, <christophe.leroy@c-s.fr>, <benh@kernel.crashing.org>, <paulus@samba.org>, <npiggin@gmail.com>, <keescook@chromium.org>, <kernel-hardening@lists.openwall.com> Cc: <linux-kernel@vger.kernel.org>, <wangkefeng.wang@huawei.com>, <yebin10@huawei.com>, <thunder.leizhen@huawei.com>, <jingxiangfeng@huawei.com>, <zhaohongjiang@huawei.com>, <oss@buserror.net>, Jason Yan <yanaijie@huawei.com> Subject: [PATCH v7 12/12] powerpc/fsl_booke/32: Document KASLR implementation Date: Fri, 20 Sep 2019 17:45:46 +0800 [thread overview] Message-ID: <20190920094546.44948-13-yanaijie@huawei.com> (raw) In-Reply-To: <20190920094546.44948-1-yanaijie@huawei.com> Add document to explain how we implement KASLR for fsl_booke32. Signed-off-by: Jason Yan <yanaijie@huawei.com> 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> --- Documentation/powerpc/kaslr-booke32.rst | 42 +++++++++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 Documentation/powerpc/kaslr-booke32.rst diff --git a/Documentation/powerpc/kaslr-booke32.rst b/Documentation/powerpc/kaslr-booke32.rst new file mode 100644 index 000000000000..8b259fdfdf03 --- /dev/null +++ b/Documentation/powerpc/kaslr-booke32.rst @@ -0,0 +1,42 @@ +.. 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. -- 2.17.2
WARNING: multiple messages have this Message-ID (diff)
From: Jason Yan <yanaijie@huawei.com> To: <mpe@ellerman.id.au>, <linuxppc-dev@lists.ozlabs.org>, <diana.craciun@nxp.com>, <christophe.leroy@c-s.fr>, <benh@kernel.crashing.org>, <paulus@samba.org>, <npiggin@gmail.com>, <keescook@chromium.org>, <kernel-hardening@lists.openwall.com> Cc: wangkefeng.wang@huawei.com, Jason Yan <yanaijie@huawei.com>, linux-kernel@vger.kernel.org, jingxiangfeng@huawei.com, oss@buserror.net, zhaohongjiang@huawei.com, thunder.leizhen@huawei.com, yebin10@huawei.com Subject: [PATCH v7 12/12] powerpc/fsl_booke/32: Document KASLR implementation Date: Fri, 20 Sep 2019 17:45:46 +0800 [thread overview] Message-ID: <20190920094546.44948-13-yanaijie@huawei.com> (raw) In-Reply-To: <20190920094546.44948-1-yanaijie@huawei.com> Add document to explain how we implement KASLR for fsl_booke32. Signed-off-by: Jason Yan <yanaijie@huawei.com> 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> --- Documentation/powerpc/kaslr-booke32.rst | 42 +++++++++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 Documentation/powerpc/kaslr-booke32.rst diff --git a/Documentation/powerpc/kaslr-booke32.rst b/Documentation/powerpc/kaslr-booke32.rst new file mode 100644 index 000000000000..8b259fdfdf03 --- /dev/null +++ b/Documentation/powerpc/kaslr-booke32.rst @@ -0,0 +1,42 @@ +.. 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. -- 2.17.2
next prev parent reply other threads:[~2019-09-20 9:25 UTC|newest] Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-09-20 9:45 [PATCH v7 00/12] implement KASLR for powerpc/fsl_booke/32 Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 01/12] powerpc: unify definition of M_IF_NEEDED Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 02/12] powerpc: move memstart_addr and kernstart_addr to init-common.c Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 03/12] powerpc: introduce kernstart_virt_addr to store the kernel base Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 04/12] powerpc/fsl_booke/32: introduce create_kaslr_tlb_entry() helper Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 05/12] powerpc/fsl_booke/32: introduce reloc_kernel_entry() helper Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 06/12] powerpc/fsl_booke/32: implement KASLR infrastructure Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 07/12] powerpc/fsl_booke/32: randomize the kernel image offset Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 08/12] powerpc/fsl_booke/kaslr: clear the original kernel if randomized Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 09/12] powerpc/fsl_booke/kaslr: support nokaslr cmdline parameter Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 10/12] powerpc/fsl_booke/kaslr: dump out kernel offset information on panic Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` [PATCH v7 11/12] powerpc/fsl_booke/kaslr: export offset in VMCOREINFO ELF notes Jason Yan 2019-09-20 9:45 ` Jason Yan 2019-09-20 9:45 ` Jason Yan [this message] 2019-09-20 9:45 ` [PATCH v7 12/12] powerpc/fsl_booke/32: Document KASLR implementation Jason Yan 2019-09-24 5:52 ` [PATCH v7 00/12] implement KASLR for powerpc/fsl_booke/32 Jason Yan 2019-09-24 5:52 ` Jason Yan 2019-10-09 6:10 ` Jason Yan 2019-10-09 6:10 ` Jason Yan 2019-10-09 7:13 ` Scott Wood 2019-10-09 7:13 ` Scott Wood 2019-10-09 7:13 ` Scott Wood 2019-10-09 8:41 ` Jason Yan 2019-10-09 8:41 ` Jason Yan 2019-10-09 18:46 ` Scott Wood 2019-10-09 18:46 ` Scott Wood 2019-10-09 18:46 ` Scott Wood 2019-10-21 3:34 ` Jason Yan 2019-10-21 3:34 ` Jason Yan 2019-10-22 23:22 ` Scott Wood 2019-10-22 23:22 ` Scott Wood 2019-10-22 23:22 ` Scott Wood
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