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Date: Wed, 28 Aug 2019 07:47:51 +0200
From: Christophe Leroy <christophe.leroy@....fr>
To: Scott Wood <oss@...error.net>, Jason Yan <yanaijie@...wei.com>
Cc: mpe@...erman.id.au, linuxppc-dev@...ts.ozlabs.org, diana.craciun@....com,
benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
keescook@...omium.org, kernel-hardening@...ts.openwall.com,
wangkefeng.wang@...wei.com, linux-kernel@...r.kernel.org,
jingxiangfeng@...wei.com, zhaohongjiang@...wei.com,
thunder.leizhen@...wei.com, fanchengyang@...wei.com, yebin10@...wei.com
Subject: Re: [PATCH v6 06/12] powerpc/fsl_booke/32: implement KASLR
infrastructure
Le 28/08/2019 à 06:54, Scott Wood a écrit :
> On Fri, Aug 09, 2019 at 06:07:54PM +0800, Jason Yan wrote:
>> This patch add support to boot kernel from places other than KERNELBASE.
>> 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.
>>
>> The offset of the kernel was not randomized yet(a fixed 64M is set). We
>> will randomize it in the next patch.
>>
>> Signed-off-by: Jason Yan <yanaijie@...wei.com>
>> Cc: Diana Craciun <diana.craciun@....com>
>> Cc: Michael Ellerman <mpe@...erman.id.au>
>> Cc: Christophe Leroy <christophe.leroy@....fr>
>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: Nicholas Piggin <npiggin@...il.com>
>> Cc: Kees Cook <keescook@...omium.org>
>> Tested-by: Diana Craciun <diana.craciun@....com>
>> Reviewed-by: Christophe Leroy <christophe.leroy@....fr>
>> ---
>> arch/powerpc/Kconfig | 11 ++++
>> arch/powerpc/kernel/Makefile | 1 +
>> arch/powerpc/kernel/early_32.c | 2 +-
>> arch/powerpc/kernel/fsl_booke_entry_mapping.S | 17 +++--
>> arch/powerpc/kernel/head_fsl_booke.S | 13 +++-
>> arch/powerpc/kernel/kaslr_booke.c | 62 +++++++++++++++++++
>> arch/powerpc/mm/mmu_decl.h | 7 +++
>> arch/powerpc/mm/nohash/fsl_booke.c | 7 ++-
>> 8 files changed, 105 insertions(+), 15 deletions(-)
>> create mode 100644 arch/powerpc/kernel/kaslr_booke.c
>>
[...]
>> diff --git a/arch/powerpc/kernel/kaslr_booke.c b/arch/powerpc/kernel/kaslr_booke.c
>> new file mode 100644
>> index 000000000000..f8dc60534ac1
>> --- /dev/null
>> +++ b/arch/powerpc/kernel/kaslr_booke.c
>
> Shouldn't this go under arch/powerpc/mm/nohash?
>
>> +/*
>> + * To see if we need to relocate the kernel to a random offset
>> + * void *dt_ptr - address of the device tree
>> + * phys_addr_t size - size of the first memory block
>> + */
>> +notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size)
>> +{
>> + unsigned long tlb_virt;
>> + phys_addr_t tlb_phys;
>> + unsigned long offset;
>> + unsigned long kernel_sz;
>> +
>> + kernel_sz = (unsigned long)_end - KERNELBASE;
>
> Why KERNELBASE and not kernstart_addr?
>
>> +
>> + offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
>> +
>> + if (offset == 0)
>> + return;
>> +
>> + kernstart_virt_addr += offset;
>> + kernstart_addr += offset;
>> +
>> + is_second_reloc = 1;
>> +
>> + if (offset >= SZ_64M) {
>> + tlb_virt = round_down(kernstart_virt_addr, SZ_64M);
>> + tlb_phys = round_down(kernstart_addr, SZ_64M);
>
> If kernstart_addr wasn't 64M-aligned before adding offset, then "offset
>> = SZ_64M" is not necessarily going to detect when you've crossed a
> mapping boundary.
>
>> +
>> + /* Create kernel map to relocate in */
>> + create_tlb_entry(tlb_phys, tlb_virt, 1);
>> + }
>> +
>> + /* Copy the kernel to it's new location and run */
>> + memcpy((void *)kernstart_virt_addr, (void *)KERNELBASE, kernel_sz);
>> +
>> + reloc_kernel_entry(dt_ptr, kernstart_virt_addr);
>> +}
>
> After copying, call flush_icache_range() on the destination.
Function copy_and_flush() does the copy and the flush. I think it should
be used instead of memcpy() + flush_icache_range()
Christophe
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