[v6,06/12] powerpc/fsl_booke/32: implement KASLR infrastructure
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Message ID 20190809100800.5426-7-yanaijie@huawei.com
State New
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Series
  • implement KASLR for powerpc/fsl_booke/32
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Commit Message

Jason Yan Aug. 9, 2019, 10:07 a.m. UTC
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@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>
Tested-by: Diana Craciun <diana.craciun@nxp.com>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.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

Comments

Scott Wood Aug. 28, 2019, 4:54 a.m. UTC | #1
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@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>
> Tested-by: Diana Craciun <diana.craciun@nxp.com>
> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.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/Kconfig b/arch/powerpc/Kconfig
> index 77f6ebf97113..710c12ef7159 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -548,6 +548,17 @@ config RELOCATABLE
>  	  setting can still be useful to bootwrappers that need to know the
>  	  load address of the kernel (eg. u-boot/mkimage).
>  
> +config RANDOMIZE_BASE
> +	bool "Randomize the address of the kernel image"
> +	depends on (FSL_BOOKE && FLATMEM && PPC32)
> +	depends on RELOCATABLE
> +	help
> +	  Randomizes the virtual address at which the kernel image is
> +	  loaded, as a security feature that deters exploit attempts
> +	  relying on knowledge of the location of kernel internals.
> +
> +	  If unsure, say N.
> +

Why is N the safe default (other than concerns about code maturity,
though arm64 and mips don't seem to have updated this recommendation
after several years)?  On x86 this defaults to Y.

> diff --git a/arch/powerpc/kernel/fsl_booke_entry_mapping.S b/arch/powerpc/kernel/fsl_booke_entry_mapping.S
> index f4d3eaae54a9..641920d4f694 100644
> --- a/arch/powerpc/kernel/fsl_booke_entry_mapping.S
> +++ b/arch/powerpc/kernel/fsl_booke_entry_mapping.S
> @@ -155,23 +155,22 @@ skpinv:	addi	r6,r6,1				/* Increment */
>  
>  #if defined(ENTRY_MAPPING_BOOT_SETUP)
>  
> -/* 6. Setup KERNELBASE mapping in TLB1[0] */
> +/* 6. Setup kernstart_virt_addr mapping in TLB1[0] */
>  	lis	r6,0x1000		/* Set MAS0(TLBSEL) = TLB1(1), ESEL = 0 */
>  	mtspr	SPRN_MAS0,r6
>  	lis	r6,(MAS1_VALID|MAS1_IPROT)@h
>  	ori	r6,r6,(MAS1_TSIZE(BOOK3E_PAGESZ_64M))@l
>  	mtspr	SPRN_MAS1,r6
> -	lis	r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, MAS2_M_IF_NEEDED)@h
> -	ori	r6,r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, MAS2_M_IF_NEEDED)@l
> -	mtspr	SPRN_MAS2,r6
> +	lis     r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@h
> +	ori     r6,r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@l
> +	and     r6,r6,r20
> +	ori	r6,r6,MAS2_M_IF_NEEDED@l
> +	mtspr   SPRN_MAS2,r6

Please use tabs rather than spaces between the mnemonic and the
arguments.

It looks like that was the last user of MAS2_VAL so let's remove it.

> 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.

> diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/fsl_booke.c
> index 556e3cd52a35..2dc27cf88add 100644
> --- a/arch/powerpc/mm/nohash/fsl_booke.c
> +++ b/arch/powerpc/mm/nohash/fsl_booke.c
> @@ -263,7 +263,8 @@ void setup_initial_memory_limit(phys_addr_t first_memblock_base,
>  int __initdata is_second_reloc;
>  notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
>  {
> -	unsigned long base = KERNELBASE;
> +	unsigned long base = kernstart_virt_addr;
> +	phys_addr_t size;
>  
>  	kernstart_addr = start;
>  	if (is_second_reloc) {
> @@ -291,7 +292,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
>  	start &= ~0x3ffffff;
>  	base &= ~0x3ffffff;
>  	virt_phys_offset = base - start;
> -	early_get_first_memblock_info(__va(dt_ptr), NULL);
> +	early_get_first_memblock_info(__va(dt_ptr), &size);
>  	/*
>  	 * We now get the memstart_addr, then we should check if this
>  	 * address is the same as what the PAGE_OFFSET map to now. If
> @@ -316,6 +317,8 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
>  		/* We should never reach here */
>  		panic("Relocation error");
>  	}
> +
> +	kaslr_early_init(__va(dt_ptr), size);

Are you assuming that available memory starts at physical address zero? 
This isn't true of some partitioning scenarios, or in a kdump crash
kernel.

-Scott
Christophe Leroy Aug. 28, 2019, 5:47 a.m. UTC | #2
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@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>
>> Tested-by: Diana Craciun <diana.craciun@nxp.com>
>> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.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
Jason Yan Aug. 28, 2019, 11:03 a.m. UTC | #3
On 2019/8/28 12:54, Scott Wood wrote:
> 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@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>
>> Tested-by: Diana Craciun <diana.craciun@nxp.com>
>> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.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/Kconfig b/arch/powerpc/Kconfig
>> index 77f6ebf97113..710c12ef7159 100644
>> --- a/arch/powerpc/Kconfig
>> +++ b/arch/powerpc/Kconfig
>> @@ -548,6 +548,17 @@ config RELOCATABLE
>>   	  setting can still be useful to bootwrappers that need to know the
>>   	  load address of the kernel (eg. u-boot/mkimage).
>>   
>> +config RANDOMIZE_BASE
>> +	bool "Randomize the address of the kernel image"
>> +	depends on (FSL_BOOKE && FLATMEM && PPC32)
>> +	depends on RELOCATABLE
>> +	help
>> +	  Randomizes the virtual address at which the kernel image is
>> +	  loaded, as a security feature that deters exploit attempts
>> +	  relying on knowledge of the location of kernel internals.
>> +
>> +	  If unsure, say N.
>> +
> 
> Why is N the safe default (other than concerns about code maturity,
> though arm64 and mips don't seem to have updated this recommendation
> after several years)?  On x86 this defaults to Y.
> 

Actually I would like to set this default Y. I was just wondering if
people like this feature or not at the beginning so I had to be more
careful.

>> diff --git a/arch/powerpc/kernel/fsl_booke_entry_mapping.S b/arch/powerpc/kernel/fsl_booke_entry_mapping.S
>> index f4d3eaae54a9..641920d4f694 100644
>> --- a/arch/powerpc/kernel/fsl_booke_entry_mapping.S
>> +++ b/arch/powerpc/kernel/fsl_booke_entry_mapping.S
>> @@ -155,23 +155,22 @@ skpinv:	addi	r6,r6,1				/* Increment */
>>   
>>   #if defined(ENTRY_MAPPING_BOOT_SETUP)
>>   
>> -/* 6. Setup KERNELBASE mapping in TLB1[0] */
>> +/* 6. Setup kernstart_virt_addr mapping in TLB1[0] */
>>   	lis	r6,0x1000		/* Set MAS0(TLBSEL) = TLB1(1), ESEL = 0 */
>>   	mtspr	SPRN_MAS0,r6
>>   	lis	r6,(MAS1_VALID|MAS1_IPROT)@h
>>   	ori	r6,r6,(MAS1_TSIZE(BOOK3E_PAGESZ_64M))@l
>>   	mtspr	SPRN_MAS1,r6
>> -	lis	r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, MAS2_M_IF_NEEDED)@h
>> -	ori	r6,r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, MAS2_M_IF_NEEDED)@l
>> -	mtspr	SPRN_MAS2,r6
>> +	lis     r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@h
>> +	ori     r6,r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@l
>> +	and     r6,r6,r20
>> +	ori	r6,r6,MAS2_M_IF_NEEDED@l
>> +	mtspr   SPRN_MAS2,r6
> 
> Please use tabs rather than spaces between the mnemonic and the
> arguments.
> 
> It looks like that was the last user of MAS2_VAL so let's remove it.
> 

OK.

>> 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?
> 

Did you mean kernstart_virt_addr? It should be kernstart_virt_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.
> 

OK

>> diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/fsl_booke.c
>> index 556e3cd52a35..2dc27cf88add 100644
>> --- a/arch/powerpc/mm/nohash/fsl_booke.c
>> +++ b/arch/powerpc/mm/nohash/fsl_booke.c
>> @@ -263,7 +263,8 @@ void setup_initial_memory_limit(phys_addr_t first_memblock_base,
>>   int __initdata is_second_reloc;
>>   notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
>>   {
>> -	unsigned long base = KERNELBASE;
>> +	unsigned long base = kernstart_virt_addr;
>> +	phys_addr_t size;
>>   
>>   	kernstart_addr = start;
>>   	if (is_second_reloc) {
>> @@ -291,7 +292,7 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
>>   	start &= ~0x3ffffff;
>>   	base &= ~0x3ffffff;
>>   	virt_phys_offset = base - start;
>> -	early_get_first_memblock_info(__va(dt_ptr), NULL);
>> +	early_get_first_memblock_info(__va(dt_ptr), &size);
>>   	/*
>>   	 * We now get the memstart_addr, then we should check if this
>>   	 * address is the same as what the PAGE_OFFSET map to now. If
>> @@ -316,6 +317,8 @@ notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
>>   		/* We should never reach here */
>>   		panic("Relocation error");
>>   	}
>> +
>> +	kaslr_early_init(__va(dt_ptr), size);
> 
> Are you assuming that available memory starts at physical address zero?
> This isn't true of some partitioning scenarios, or in a kdump crash
> kernel.
> 

I'm not assuming that but I haven't tested that case for now. I will 
reconsider and test these scenarios and fix all bugs.

> -Scott
> 
> .
>
Scott Wood Aug. 28, 2019, 4:44 p.m. UTC | #4
On Wed, 2019-08-28 at 19:03 +0800, Jason Yan wrote:
> 
> On 2019/8/28 12:54, Scott Wood wrote:
> > On Fri, Aug 09, 2019 at 06:07:54PM +0800, Jason Yan wrote:
> > > +/*
> > > + * 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?
> > 
> 
> Did you mean kernstart_virt_addr? It should be kernstart_virt_addr.

Yes, kernstart_virt_addr.  KERNELBASE will be incorrect if the kernel was
loaded at a nonzero physical address without CONFIG_PHYSICAL_START being
adjusted to match.

-Scott
Jason Yan Aug. 29, 2019, 6:26 a.m. UTC | #5
On 2019/8/28 13:47, Christophe Leroy wrote:
> 
> 
> 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@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>
>>> Tested-by: Diana Craciun <diana.craciun@nxp.com>
>>> Reviewed-by: Christophe Leroy <christophe.leroy@c-s.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()
> 

Hi Christophe,

Thanks for the suggestion. But I think copy_and_flush() is not included 
in fsl booke code, maybe move this function to misc.S?

> Christophe
> 
> .
>

Patch
diff mbox series

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 77f6ebf97113..710c12ef7159 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -548,6 +548,17 @@  config RELOCATABLE
 	  setting can still be useful to bootwrappers that need to know the
 	  load address of the kernel (eg. u-boot/mkimage).
 
+config RANDOMIZE_BASE
+	bool "Randomize the address of the kernel image"
+	depends on (FSL_BOOKE && FLATMEM && PPC32)
+	depends on RELOCATABLE
+	help
+	  Randomizes the virtual address at which the kernel image is
+	  loaded, as a security feature that deters exploit attempts
+	  relying on knowledge of the location of kernel internals.
+
+	  If unsure, say N.
+
 config RELOCATABLE_TEST
 	bool "Test relocatable kernel"
 	depends on (PPC64 && RELOCATABLE)
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index ea0c69236789..32f6c5b99307 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -106,6 +106,7 @@  extra-$(CONFIG_PPC_8xx)		:= head_8xx.o
 extra-y				+= vmlinux.lds
 
 obj-$(CONFIG_RELOCATABLE)	+= reloc_$(BITS).o
+obj-$(CONFIG_RANDOMIZE_BASE)	+= kaslr_booke.o
 
 obj-$(CONFIG_PPC32)		+= entry_32.o setup_32.o early_32.o
 obj-$(CONFIG_PPC64)		+= dma-iommu.o iommu.o
diff --git a/arch/powerpc/kernel/early_32.c b/arch/powerpc/kernel/early_32.c
index 3482118ffe76..0c5849fd936d 100644
--- a/arch/powerpc/kernel/early_32.c
+++ b/arch/powerpc/kernel/early_32.c
@@ -32,5 +32,5 @@  notrace unsigned long __init early_init(unsigned long dt_ptr)
 
 	apply_feature_fixups();
 
-	return KERNELBASE + offset;
+	return kernstart_virt_addr + offset;
 }
diff --git a/arch/powerpc/kernel/fsl_booke_entry_mapping.S b/arch/powerpc/kernel/fsl_booke_entry_mapping.S
index f4d3eaae54a9..641920d4f694 100644
--- a/arch/powerpc/kernel/fsl_booke_entry_mapping.S
+++ b/arch/powerpc/kernel/fsl_booke_entry_mapping.S
@@ -155,23 +155,22 @@  skpinv:	addi	r6,r6,1				/* Increment */
 
 #if defined(ENTRY_MAPPING_BOOT_SETUP)
 
-/* 6. Setup KERNELBASE mapping in TLB1[0] */
+/* 6. Setup kernstart_virt_addr mapping in TLB1[0] */
 	lis	r6,0x1000		/* Set MAS0(TLBSEL) = TLB1(1), ESEL = 0 */
 	mtspr	SPRN_MAS0,r6
 	lis	r6,(MAS1_VALID|MAS1_IPROT)@h
 	ori	r6,r6,(MAS1_TSIZE(BOOK3E_PAGESZ_64M))@l
 	mtspr	SPRN_MAS1,r6
-	lis	r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, MAS2_M_IF_NEEDED)@h
-	ori	r6,r6,MAS2_VAL(PAGE_OFFSET, BOOK3E_PAGESZ_64M, MAS2_M_IF_NEEDED)@l
-	mtspr	SPRN_MAS2,r6
+	lis     r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@h
+	ori     r6,r6,MAS2_EPN_MASK(BOOK3E_PAGESZ_64M)@l
+	and     r6,r6,r20
+	ori	r6,r6,MAS2_M_IF_NEEDED@l
+	mtspr   SPRN_MAS2,r6
 	mtspr	SPRN_MAS3,r8
 	tlbwe
 
-/* 7. Jump to KERNELBASE mapping */
-	lis	r6,(KERNELBASE & ~0xfff)@h
-	ori	r6,r6,(KERNELBASE & ~0xfff)@l
-	rlwinm	r7,r25,0,0x03ffffff
-	add	r6,r7,r6
+/* 7. Jump to kernstart_virt_addr mapping */
+	mr	r6,r20
 
 #elif defined(ENTRY_MAPPING_KEXEC_SETUP)
 /*
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index 2083382dd662..f7a5c5f03c72 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -155,6 +155,8 @@  _ENTRY(_start);
  */
 
 _ENTRY(__early_start)
+	LOAD_REG_ADDR_PIC(r20, kernstart_virt_addr)
+	lwz     r20,0(r20)
 
 #define ENTRY_MAPPING_BOOT_SETUP
 #include "fsl_booke_entry_mapping.S"
@@ -277,8 +279,8 @@  set_ivor:
 	ori	r6, r6, swapper_pg_dir@l
 	lis	r5, abatron_pteptrs@h
 	ori	r5, r5, abatron_pteptrs@l
-	lis	r4, KERNELBASE@h
-	ori	r4, r4, KERNELBASE@l
+	lis     r3, kernstart_virt_addr@ha
+	lwz     r4, kernstart_virt_addr@l(r3)
 	stw	r5, 0(r4)	/* Save abatron_pteptrs at a fixed location */
 	stw	r6, 0(r5)
 
@@ -1067,7 +1069,12 @@  __secondary_start:
 	mr	r5,r25		/* phys kernel start */
 	rlwinm	r5,r5,0,~0x3ffffff	/* aligned 64M */
 	subf	r4,r5,r4	/* memstart_addr - phys kernel start */
-	li	r5,0		/* no device tree */
+	lis	r7,KERNELBASE@h
+	ori	r7,r7,KERNELBASE@l
+	cmpw	r20,r7		/* if kimage_vaddr != KERNELBASE, randomized */
+	beq	2f
+	li	r4,0
+2:	li	r5,0		/* no device tree */
 	li	r6,0		/* not boot cpu */
 	bl	restore_to_as0
 
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
@@ -0,0 +1,62 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+//
+// Copyright (C) 2019 Jason Yan <yanaijie@huawei.com>
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/stddef.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/memblock.h>
+#include <asm/pgalloc.h>
+#include <asm/prom.h>
+#include <mm/mmu_decl.h>
+
+static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size,
+						  unsigned long kernel_sz)
+{
+	/* return a fixed offset of 64M for now */
+	return SZ_64M;
+}
+
+/*
+ * 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;
+
+	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);
+
+		/* 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);
+}
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index 804da298beb3..213997d69729 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -144,10 +144,17 @@  extern int switch_to_as1(void);
 extern void restore_to_as0(int esel, int offset, void *dt_ptr, int bootcpu);
 void create_tlb_entry(phys_addr_t phys, unsigned long virt, int entry);
 void reloc_kernel_entry(void *fdt, int addr);
+extern int is_second_reloc;
 #endif
 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);
+#else
+static inline void kaslr_early_init(void *dt_ptr, phys_addr_t size) {}
+#endif
+
 struct tlbcam {
 	u32	MAS0;
 	u32	MAS1;
diff --git a/arch/powerpc/mm/nohash/fsl_booke.c b/arch/powerpc/mm/nohash/fsl_booke.c
index 556e3cd52a35..2dc27cf88add 100644
--- a/arch/powerpc/mm/nohash/fsl_booke.c
+++ b/arch/powerpc/mm/nohash/fsl_booke.c
@@ -263,7 +263,8 @@  void setup_initial_memory_limit(phys_addr_t first_memblock_base,
 int __initdata is_second_reloc;
 notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
 {
-	unsigned long base = KERNELBASE;
+	unsigned long base = kernstart_virt_addr;
+	phys_addr_t size;
 
 	kernstart_addr = start;
 	if (is_second_reloc) {
@@ -291,7 +292,7 @@  notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
 	start &= ~0x3ffffff;
 	base &= ~0x3ffffff;
 	virt_phys_offset = base - start;
-	early_get_first_memblock_info(__va(dt_ptr), NULL);
+	early_get_first_memblock_info(__va(dt_ptr), &size);
 	/*
 	 * We now get the memstart_addr, then we should check if this
 	 * address is the same as what the PAGE_OFFSET map to now. If
@@ -316,6 +317,8 @@  notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
 		/* We should never reach here */
 		panic("Relocation error");
 	}
+
+	kaslr_early_init(__va(dt_ptr), size);
 }
 #endif
 #endif