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Subject: Re: [PATCH v3 3/6] powerpc/fsl_booke/64: implement KASLR for
 fsl_booke64
From:   Jason Yan <yanaijie@huawei.com>
To:     Christophe Leroy <christophe.leroy@c-s.fr>, <mpe@ellerman.id.au>,
        <linuxppc-dev@lists.ozlabs.org>, <diana.craciun@nxp.com>,
        <benh@kernel.crashing.org>, <paulus@samba.org>,
        <npiggin@gmail.com>, <keescook@chromium.org>,
        <kernel-hardening@lists.openwall.com>, <oss@buserror.net>
CC:     <linux-kernel@vger.kernel.org>, <zhaohongjiang@huawei.com>
References: <20200206025825.22934-1-yanaijie@huawei.com>
 <20200206025825.22934-4-yanaijie@huawei.com>
 <41b9f1ca-c6fd-291a-2c96-2a0e8a754ec4@c-s.fr>
 <dbe0b316-40a2-7da4-c26b-e59efa555400@huawei.com>
Message-ID: <d3647cce-ece3-d302-f541-b02b1f2b5e9e@huawei.com>
Date:   Wed, 26 Feb 2020 11:33:37 +0800
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在 2020/2/26 10:40, Jason Yan 写道:
> 
> 
> 在 2020/2/20 21:48, Christophe Leroy 写道:
>>
>>
>> Le 06/02/2020 à 03:58, Jason Yan a écrit :
>>> The implementation for Freescale BookE64 is similar as 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.
>>>
>>> To support secondary cpu boot up, a variable __kaslr_offset was added in
>>> first_256B section. This can help secondary cpu get the kaslr offset
>>> before the 1:1 mapping has been setup.
>>>
>>> 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>
>>> ---
>>>   arch/powerpc/Kconfig                 |  2 +-
>>>   arch/powerpc/kernel/exceptions-64e.S | 10 +++++++++
>>>   arch/powerpc/kernel/head_64.S        |  7 ++++++
>>>   arch/powerpc/kernel/setup_64.c       |  4 +++-
>>>   arch/powerpc/mm/mmu_decl.h           | 16 +++++++-------
>>>   arch/powerpc/mm/nohash/kaslr_booke.c | 33 +++++++++++++++++++++++++---
>>>   6 files changed, 59 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>> index c150a9d49343..754aeb96bb1c 100644
>>> --- a/arch/powerpc/Kconfig
>>> +++ b/arch/powerpc/Kconfig
>>> @@ -568,7 +568,7 @@ config RELOCATABLE
>>>   config RANDOMIZE_BASE
>>>       bool "Randomize the address of the kernel image"
>>> -    depends on (FSL_BOOKE && FLATMEM && PPC32)
>>> +    depends on (PPC_FSL_BOOK3E && FLATMEM)
>>>       depends on RELOCATABLE
>>>       help
>>>         Randomizes the virtual address at which the kernel image is
>>> diff --git a/arch/powerpc/kernel/exceptions-64e.S 
>>> b/arch/powerpc/kernel/exceptions-64e.S
>>> index 1b9b174bee86..c1c05b8684ca 100644
>>> --- a/arch/powerpc/kernel/exceptions-64e.S
>>> +++ b/arch/powerpc/kernel/exceptions-64e.S
>>> @@ -1378,6 +1378,7 @@ skpinv:    addi    r6,r6,1                /* 
>>> Increment */
>>>   1:    mflr    r6
>>>       addi    r6,r6,(2f - 1b)
>>>       tovirt(r6,r6)
>>> +    add    r6,r6,r19
>>>       lis    r7,MSR_KERNEL@h
>>>       ori    r7,r7,MSR_KERNEL@l
>>>       mtspr    SPRN_SRR0,r6
>>> @@ -1400,6 +1401,7 @@ skpinv:    addi    r6,r6,1                /* 
>>> Increment */
>>>       /* We translate LR and return */
>>>       tovirt(r8,r8)
>>> +    add    r8,r8,r19
>>>       mtlr    r8
>>>       blr
>>> @@ -1528,6 +1530,7 @@ a2_tlbinit_code_end:
>>>    */
>>>   _GLOBAL(start_initialization_book3e)
>>>       mflr    r28
>>> +    li    r19, 0
>>>       /* First, we need to setup some initial TLBs to map the kernel
>>>        * text, data and bss at PAGE_OFFSET. We don't have a real mode
>>> @@ -1570,6 +1573,12 @@ _GLOBAL(book3e_secondary_core_init)
>>>       cmplwi    r4,0
>>>       bne    2f
>>> +    li    r19, 0
>>> +#ifdef CONFIG_RANDOMIZE_BASE
>>> +    LOAD_REG_ADDR_PIC(r19, __kaslr_offset)
>>> +    lwz    r19,0(r19)
>>> +    rlwinm  r19,r19,0,0,5
>>> +#endif
>>>       /* Setup TLB for this core */
>>>       bl    initial_tlb_book3e
>>> @@ -1602,6 +1611,7 @@ _GLOBAL(book3e_secondary_core_init)
>>>       lis    r3,PAGE_OFFSET@highest
>>>       sldi    r3,r3,32
>>>       or    r28,r28,r3
>>> +    add    r28,r28,r19
>>>   1:    mtlr    r28
>>>       blr
>>> diff --git a/arch/powerpc/kernel/head_64.S 
>>> b/arch/powerpc/kernel/head_64.S
>>> index ad79fddb974d..744624140fb8 100644
>>> --- a/arch/powerpc/kernel/head_64.S
>>> +++ b/arch/powerpc/kernel/head_64.S
>>> @@ -104,6 +104,13 @@ __secondary_hold_acknowledge:
>>>       .8byte    0x0
>>>   #ifdef CONFIG_RELOCATABLE
>>> +#ifdef CONFIG_RANDOMIZE_BASE
>>> +    . = 0x58
>>> +    .globl    __kaslr_offset
>>> +__kaslr_offset:
>>> +DEFINE_FIXED_SYMBOL(__kaslr_offset)
>>> +    .long    0
>>> +#endif
>>>       /* This flag is set to 1 by a loader if the kernel should run
>>>        * at the loaded address instead of the linked address.  This
>>>        * is used by kexec-tools to keep the the kdump kernel in the
>>> diff --git a/arch/powerpc/kernel/setup_64.c 
>>> b/arch/powerpc/kernel/setup_64.c
>>> index 6104917a282d..a16b970a8d1a 100644
>>> --- a/arch/powerpc/kernel/setup_64.c
>>> +++ b/arch/powerpc/kernel/setup_64.c
>>> @@ -66,7 +66,7 @@
>>>   #include <asm/feature-fixups.h>
>>>   #include <asm/kup.h>
>>>   #include <asm/early_ioremap.h>
>>> -
>>
>> Why remove this new line which clearly separates things in asm/ and 
>> things in local dir ?
> 
> Sorry to break this. I will add the new line back.
> 
>>
>>> +#include <mm/mmu_decl.h>
>>>   #include "setup.h"
>>>   int spinning_secondaries;
>>> @@ -300,6 +300,8 @@ void __init early_setup(unsigned long dt_ptr)
>>>       /* Enable early debugging if any specified (see udbg.h) */
>>>       udbg_early_init();
>>> +    kaslr_early_init(__va(dt_ptr), 0);
>>> +
>>>       udbg_printf(" -> %s(), dt_ptr: 0x%lx\n", __func__, dt_ptr);
>>>       /*
>>> diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
>>> index 3e1c85c7d10b..bbd721d1e3d7 100644
>>> --- a/arch/powerpc/mm/mmu_decl.h
>>> +++ b/arch/powerpc/mm/mmu_decl.h
>>> @@ -147,14 +147,6 @@ void reloc_kernel_entry(void *fdt, long addr);
>>>   extern void loadcam_entry(unsigned int index);
>>>   extern void loadcam_multi(int first_idx, int num, int tmp_idx);
>>> -#ifdef CONFIG_RANDOMIZE_BASE
>>> -void kaslr_early_init(void *dt_ptr, phys_addr_t size);
>>> -void kaslr_late_init(void);
>>> -#else
>>> -static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
>>> -static inline void kaslr_late_init(void) {}
>>> -#endif
>>> -
>>>   struct tlbcam {
>>>       u32    MAS0;
>>>       u32    MAS1;
>>> @@ -164,6 +156,14 @@ struct tlbcam {
>>>   };
>>>   #endif
>>> +#ifdef CONFIG_RANDOMIZE_BASE
>>> +void kaslr_early_init(void *dt_ptr, phys_addr_t size);
>>> +void kaslr_late_init(void);
>>> +#else
>>> +static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
>>> +static inline void kaslr_late_init(void) {}
>>> +#endif
>>> +
>>>   #if defined(CONFIG_PPC_BOOK3S_32) || defined(CONFIG_FSL_BOOKE) || 
>>> defined(CONFIG_PPC_8xx)
>>>   /* 6xx have BATS */
>>>   /* FSL_BOOKE have TLBCAM */
>>> diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c 
>>> b/arch/powerpc/mm/nohash/kaslr_booke.c
>>> index 07b036e98353..c6f5c1db1394 100644
>>> --- a/arch/powerpc/mm/nohash/kaslr_booke.c
>>> +++ b/arch/powerpc/mm/nohash/kaslr_booke.c
>>> @@ -231,7 +231,7 @@ static __init unsigned long 
>>> get_usable_address(const void *fdt,
>>>       unsigned long pa;
>>>       unsigned long pa_end;
>>> -    for (pa = offset; (long)pa > (long)start; pa -= SZ_16K) {
>>> +    for (pa = offset; (long)pa > (long)start; pa -= SZ_64K) {
>>
>> Doesn't this modify the behaviour for PPC32 too ?
> 
> Oh, yes. I will fix this.
> 
>>
>>>           pa_end = pa + regions.kernel_size;
>>>           if (overlaps_region(fdt, pa, pa_end))
>>>               continue;
>>> @@ -265,14 +265,14 @@ static unsigned long __init 
>>> kaslr_legal_offset(void *dt_ptr, unsigned long rando
>>>   {
>>>       unsigned long koffset = 0;
>>>       unsigned long start;
>>> -    unsigned long index;
>>>       unsigned long offset;
>>> +#ifdef CONFIG_PPC32
>>
>> Can we use
>>
>> if (IS_ENABLED(CONFIG_PPC32)) {
>>      /* 32 bits stuff */
>> } else {
>>      /* 64 bits stuff */
>> }
> 
> Thansk for the suggestion. I will consider to use IS_ENABLED() instead.
> 
>>
>>>       /*
>>>        * Decide which 64M we want to start
>>>        * Only use the low 8 bits of the random seed
>>>        */
>>> -    index = random & 0xFF;
>>> +    unsigned long index = random & 0xFF;
>>
>> That's not good in terms of readability, index declaration should 
>> remain at the top of the function, should be possible if using 
>> IS_ENABLED() instead
> 
> I'm wondering how to declare a variable inside a code block such as if 
> (IS_ENABLED(CONFIG_PPC32)) at the top of the function and use the 
> variable in another if (IS_ENABLED(CONFIG_PPC32)). Is there any good idea?
> 

Hi Christophe,

When using a standard C if/else, all code compiled for PPC32 and PPC64, 
but this will bring some build error because not all variables both 
defined for PPC32 and PPC64.

[yanaijie@138 linux]$ sh ppc64build.sh
   CALL    scripts/atomic/check-atomics.sh
   CALL    scripts/checksyscalls.sh
   CHK     include/generated/compile.h
   CC      arch/powerpc/mm/nohash/kaslr_booke.o
arch/powerpc/mm/nohash/kaslr_booke.c: In function 'kaslr_choose_location':
arch/powerpc/mm/nohash/kaslr_booke.c:341:30: error: 
'CONFIG_LOWMEM_CAM_NUM' undeclared (first use in this function); did you 
mean 'CONFIG_FLATMEM_MANUAL'?
    ram = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM, true);
                               ^~~~~~~~~~~~~~~~~~~~~
                               CONFIG_FLATMEM_MANUAL
arch/powerpc/mm/nohash/kaslr_booke.c:341:30: note: each undeclared 
identifier is reported only once for each function it appears in
arch/powerpc/mm/nohash/kaslr_booke.c: In function 'kaslr_early_init':
arch/powerpc/mm/nohash/kaslr_booke.c:404:3: error: 'is_second_reloc' 
undeclared (first use in this function); did you mean '__cond_lock'?
    is_second_reloc = 1;
    ^~~~~~~~~~~~~~~
    __cond_lock
arch/powerpc/mm/nohash/kaslr_booke.c:411:4: error: implicit declaration 
of function 'create_kaslr_tlb_entry'; did you mean 'reloc_kernel_entry'? 
[-Werror=implicit-function-declaration]
     create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
     ^~~~~~~~~~~~~~~~~~~~~~
     reloc_kernel_entry
cc1: all warnings being treated as errors
make[3]: *** [scripts/Makefile.build:268: 
arch/powerpc/mm/nohash/kaslr_booke.o] Error 1
make[2]: *** [scripts/Makefile.build:505: arch/powerpc/mm/nohash] Error 2
make[1]: *** [scripts/Makefile.build:505: arch/powerpc/mm] Error 2
make: *** [Makefile:1681: arch/powerpc] Error 2

Thanks,
Jason

>>
>>>       index %= regions.linear_sz / SZ_64M;
>>>       /* Decide offset inside 64M */
>>> @@ -287,6 +287,15 @@ static unsigned long __init 
>>> kaslr_legal_offset(void *dt_ptr, unsigned long rando
>>>               break;
>>>           index--;
>>>       }
>>> +#else
>>> +    /* Decide kernel offset inside 1G */
>>> +    offset = random % (SZ_1G - regions.kernel_size);
>>> +    offset = round_down(offset, SZ_64K);
>>> +
>>> +    start = memstart_addr;
>>> +    offset = memstart_addr + offset;
>>> +    koffset = get_usable_address(dt_ptr, start, offset);
>>> +#endif
>>>       if (koffset != 0)
>>>           koffset -= memstart_addr;
>>> @@ -325,6 +334,7 @@ static unsigned long __init 
>>> kaslr_choose_location(void *dt_ptr, phys_addr_t size
>>>       else
>>>           pr_warn("KASLR: No safe seed for randomizing the kernel 
>>> base.\n");
>>> +#ifdef CONFIG_PPC32
>>>       ram = min_t(phys_addr_t, __max_low_memory, size);
>>>       ram = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM, true);
>>>       linear_sz = min_t(unsigned long, ram, SZ_512M);
>>> @@ -332,6 +342,7 @@ static unsigned long __init 
>>> kaslr_choose_location(void *dt_ptr, phys_addr_t size
>>>       /* If the linear size is smaller than 64M, do not randmize */
>>>       if (linear_sz < SZ_64M)
>>>           return 0;
>>> +#endif
>>>       /* check for a reserved-memory node and record its cell sizes */
>>>       regions.reserved_mem = fdt_path_offset(dt_ptr, 
>>> "/reserved-memory");
>>> @@ -363,6 +374,17 @@ notrace void __init kaslr_early_init(void 
>>> *dt_ptr, phys_addr_t size)
>>>       unsigned long offset;
>>>       unsigned long kernel_sz;
>>> +#ifdef CONFIG_PPC64
>>
>> Same, can we use a standard C if/else sequence with 
>> IS_ENABLED(CONFIG_PPC64) ?
> 
> OK, I will try to do this if I can deal with the declaration of 
> variables in different if/else sequence.
> 
> Thanks,
> Jason
> 
> 
>>
>>> +    unsigned int *__kaslr_offset = (unsigned int *)(KERNELBASE + 0x58);
>>> +    unsigned int *__run_at_load = (unsigned int *)(KERNELBASE + 0x5c);
>>> +
>>> +    if (*__run_at_load == 1)
>>> +        return;
>>> +
>>> +    /* Setup flat device-tree pointer */
>>> +    initial_boot_params = dt_ptr;
>>> +#endif
>>> +
>>>       kernel_sz = (unsigned long)_end - (unsigned long)_stext;
>>>       offset = kaslr_choose_location(dt_ptr, size, kernel_sz);
>>> @@ -372,6 +394,7 @@ notrace void __init kaslr_early_init(void 
>>> *dt_ptr, phys_addr_t size)
>>>       kernstart_virt_addr += offset;
>>>       kernstart_addr += offset;
>>> +#ifdef CONFIG_PPC32
>>>       is_second_reloc = 1;
>>>       if (offset >= SZ_64M) {
>>> @@ -381,6 +404,10 @@ notrace void __init kaslr_early_init(void 
>>> *dt_ptr, phys_addr_t size)
>>>           /* Create kernel map to relocate in */
>>>           create_kaslr_tlb_entry(1, tlb_virt, tlb_phys);
>>>       }
>>> +#else
>>> +    *__kaslr_offset = kernstart_virt_addr - KERNELBASE;
>>> +    *__run_at_load = 1;
>>> +#endif
>>>       /* Copy the kernel to it's new location and run */
>>>       memcpy((void *)kernstart_virt_addr, (void *)_stext, kernel_sz);
>>>
>>
>> Christophe
>>
>> .
> 
> 
> .