linux-kernel - Re: [PATCH v3 1/6] powerpc/fsl_booke/kaslr: refactor kaslr_legal_offset() and kaslr_early

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Message-ID: <f80cce40-804e-12a3-7429-74923a3cb7f7@huawei.com>
Date:   Wed, 26 Feb 2020 10:11:16 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     Christophe Leroy <christophe.leroy@....fr>, <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>, <oss@...error.net>
CC:     <linux-kernel@...r.kernel.org>, <zhaohongjiang@...wei.com>
Subject: Re: [PATCH v3 1/6] powerpc/fsl_booke/kaslr: refactor
 kaslr_legal_offset() and kaslr_early_init()



在 2020/2/20 21:40, Christophe Leroy 写道:
> 
> 
> Le 06/02/2020 à 03:58, Jason Yan a écrit :
>> Some code refactor in kaslr_legal_offset() and kaslr_early_init(). No
>> functional change. This is a preparation for KASLR fsl_booke64.
>>
>> Signed-off-by: Jason Yan <yanaijie@...wei.com>
>> Cc: Scott Wood <oss@...error.net>
>> 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>
>> ---
>>   arch/powerpc/mm/nohash/kaslr_booke.c | 40 ++++++++++++++--------------
>>   1 file changed, 20 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c 
>> b/arch/powerpc/mm/nohash/kaslr_booke.c
>> index 4a75f2d9bf0e..07b036e98353 100644
>> --- a/arch/powerpc/mm/nohash/kaslr_booke.c
>> +++ b/arch/powerpc/mm/nohash/kaslr_booke.c
>> @@ -25,6 +25,7 @@ struct regions {
>>       unsigned long pa_start;
>>       unsigned long pa_end;
>>       unsigned long kernel_size;
>> +    unsigned long linear_sz;
>>       unsigned long dtb_start;
>>       unsigned long dtb_end;
>>       unsigned long initrd_start;
>> @@ -260,11 +261,23 @@ static __init void get_cell_sizes(const void 
>> *fdt, int node, int *addr_cells,
>>           *size_cells = fdt32_to_cpu(*prop);
>>   }
>> -static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned 
>> long index,
>> -                           unsigned long offset)
>> +static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned 
>> long random)
>>   {
>>       unsigned long koffset = 0;
>>       unsigned long start;
>> +    unsigned long index;
>> +    unsigned long offset;
>> +
>> +    /*
>> +     * Decide which 64M we want to start
>> +     * Only use the low 8 bits of the random seed
>> +     */
>> +    index = random & 0xFF;
>> +    index %= regions.linear_sz / SZ_64M;
>> +
>> +    /* Decide offset inside 64M */
>> +    offset = random % (SZ_64M - regions.kernel_size);
>> +    offset = round_down(offset, SZ_16K);
>>       while ((long)index >= 0) {
>>           offset = memstart_addr + index * SZ_64M + offset;
>> @@ -289,10 +302,9 @@ static inline __init bool kaslr_disabled(void)
>>   static unsigned long __init kaslr_choose_location(void *dt_ptr, 
>> phys_addr_t size,
>>                             unsigned long kernel_sz)
>>   {
>> -    unsigned long offset, random;
>> +    unsigned long random;
>>       unsigned long ram, linear_sz;
>>       u64 seed;
>> -    unsigned long index;
>>       kaslr_get_cmdline(dt_ptr);
>>       if (kaslr_disabled())
>> @@ -333,22 +345,12 @@ static unsigned long __init 
>> kaslr_choose_location(void *dt_ptr, phys_addr_t size
>>       regions.dtb_start = __pa(dt_ptr);
>>       regions.dtb_end = __pa(dt_ptr) + fdt_totalsize(dt_ptr);
>>       regions.kernel_size = kernel_sz;
>> +    regions.linear_sz = linear_sz;
>>       get_initrd_range(dt_ptr);
>>       get_crash_kernel(dt_ptr, ram);
>> -    /*
>> -     * Decide which 64M we want to start
>> -     * Only use the low 8 bits of the random seed
>> -     */
>> -    index = random & 0xFF;
>> -    index %= linear_sz / SZ_64M;
>> -
>> -    /* Decide offset inside 64M */
>> -    offset = random % (SZ_64M - kernel_sz);
>> -    offset = round_down(offset, SZ_16K);
>> -
>> -    return kaslr_legal_offset(dt_ptr, index, offset);
>> +    return kaslr_legal_offset(dt_ptr, random);
>>   }
>>   /*
>> @@ -358,8 +360,6 @@ static unsigned long __init 
>> kaslr_choose_location(void *dt_ptr, phys_addr_t size
>>    */
>>   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;
>> @@ -375,8 +375,8 @@ notrace void __init kaslr_early_init(void *dt_ptr, 
>> phys_addr_t size)
>>       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);
>> +        unsigned long tlb_virt = round_down(kernstart_virt_addr, 
>> SZ_64M);
>> +        phys_addr_t tlb_phys = round_down(kernstart_addr, SZ_64M);
> 
> That looks like cleanup unrelated to the patch itself.

Hi, Christophe

These two variables is only for the booke32 code, so I moved the
definition here so that I can save a "#ifdef CONFIG_PPC32" for them.

Thanks,
Jason

> 
>>           /* Create kernel map to relocate in */
>>           create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
>>
> 
> Christophe
> 
> .