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Message-ID: <dbe0b316-40a2-7da4-c26b-e59efa555400@huawei.com>
Date: Wed, 26 Feb 2020 10:40:30 +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 3/6] powerpc/fsl_booke/64: implement KASLR for
fsl_booke64
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@...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/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@...hest
>> 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?
>
>> 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
>
> .
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