[PATCH 1/3] MIPS: KASLR: Correcte valid bits in apply_r_mips_26_rel

[PATCH 1/3] MIPS: KASLR: Correcte valid bits in apply_r_mips_26_rel

[Jinyang He]

Apply_r_mips_26_rel() relocates instructions like j, jal and etc. These
instructions consist of 6bits function field and 26bits address field.
The value of target_addr as follows,
=================================================================
|     high 4bits           |            low 28bits              |
=================================================================
|the high 4bits of this PC | the low 26bits of instructions << 2|
=================================================================
Thus, loc_orig and log_new both need high 4bits ranther than high 6bits.
Replace 0x3ffffff with 0xfffffff.

Signed-off-by: Jinyang He <hejinyang@loongson.cn>
---
 arch/mips/kernel/relocate.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
index 3d80a51..709cfa0 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -95,7 +95,7 @@ static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
 
 	/* Original target address */
 	target_addr <<= 2;
-	target_addr += (unsigned long)loc_orig & ~0x03ffffff;
+	target_addr += (unsigned long)loc_orig & ~0x0fffffff;
 
 	/* Get the new target address */
 	target_addr += offset;
@@ -105,7 +105,7 @@ static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
 		return -ENOEXEC;
 	}
 
-	target_addr -= (unsigned long)loc_new & ~0x03ffffff;
+	target_addr -= (unsigned long)loc_new & ~0x0fffffff;
 	target_addr >>= 2;
 
 	*loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
-- 
2.1.0

[PATCH 2/3] MIPS: Loongson64: Add KASLR support

[Jinyang He]

Provide null return plat_get_fdt(). Loongson64 start supporting KASLR.

Signed-off-by: Jinyang He <hejinyang@loongson.cn>
---
 arch/mips/Kconfig            | 4 +++-
 arch/mips/loongson64/setup.c | 7 +++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 0f638bf..1508829 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -488,6 +488,7 @@ config MACH_LOONGSON64
 	select SYS_SUPPORTS_HIGHMEM
 	select SYS_SUPPORTS_LITTLE_ENDIAN
 	select SYS_SUPPORTS_ZBOOT
+	select SYS_SUPPORTS_RELOCATABLE
 	select ZONE_DMA32
 	select NUMA
 	select SMP
@@ -2778,7 +2779,8 @@ config RELOCATABLE
 	depends on CPU_MIPS32_R2 || CPU_MIPS64_R2 || \
 		   CPU_MIPS32_R5 || CPU_MIPS64_R5 || \
 		   CPU_MIPS32_R6 || CPU_MIPS64_R6 || \
-		   CPU_P5600 || CAVIUM_OCTEON_SOC
+		   CPU_P5600 || CAVIUM_OCTEON_SOC || \
+		   CPU_LOONGSON64
 	help
 	  This builds a kernel image that retains relocation information
 	  so it can be loaded someplace besides the default 1MB.
diff --git a/arch/mips/loongson64/setup.c b/arch/mips/loongson64/setup.c
index 6fe3fff..5a5b745 100644
--- a/arch/mips/loongson64/setup.c
+++ b/arch/mips/loongson64/setup.c
@@ -31,6 +31,13 @@ static void wbflush_loongson(void)
 void (*__wbflush)(void) = wbflush_loongson;
 EXPORT_SYMBOL(__wbflush);
 
+#ifdef CONFIG_RELOCATABLE
+void __init *plat_get_fdt(void)
+{
+		return NULL;
+}
+#endif
+
 void __init plat_mem_setup(void)
 {
 	if (loongson_fdt_blob)
-- 
2.1.0

[PATCH 3/3] MIPS: KASLR: Make relocation_address can be configured

[Jinyang He]

When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
always returns a constant. It is not friendly to users if the address
cannot be used. Make it can be configured at Kconfig.

Signed-off-by: Jinyang He <hejinyang@loongson.cn>
---
 arch/mips/Kconfig           | 5 +++++
 arch/mips/kernel/relocate.c | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 1508829..1c95478 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2803,6 +2803,11 @@ config RELOCATION_TABLE_SIZE
 
 	  If unsure, leave at the default value.
 
+config RELOCATE_DESTINATION
+	hex "Relocate address when RANDOMIZE_BASE is not set"
+	depends on RELOCATABLE && !RANDOMIZE_BASE
+	default "0xffffffff81000000"
+
 config RANDOMIZE_BASE
 	bool "Randomize the address of the kernel image"
 	depends on RELOCATABLE
diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
index 709cfa0..b7ea6ff 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -276,7 +276,7 @@ static inline void __init *determine_relocation_address(void)
 	 * Choose a new address for the kernel
 	 * For now we'll hard code the destination
 	 */
-	return (void *)0xffffffff81000000;
+	return (void *)CONFIG_RELOCATE_DESTINATION;
 }
 
 #endif
-- 
2.1.0

Re: [PATCH 3/3] MIPS: KASLR: Make relocation_address can be configured

[Sergei Shtylyov]

Hello!

On 19.11.2020 5:29, Jinyang He wrote:

> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
> always returns a constant. It is not friendly to users if the address
> cannot be used. Make it can be configured at Kconfig.

    Make it configurable?

> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
[...]

MBR, Sergei

Re: [PATCH 3/3] MIPS: KASLR: Make relocation_address can be configured

[Jinyang He]

Hi,

On 11/19/2020 04:06 PM, Sergei Shtylyov wrote:
> Hello!
>
> On 19.11.2020 5:29, Jinyang He wrote:
>
>> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
>> always returns a constant. It is not friendly to users if the address
>> cannot be used. Make it can be configured at Kconfig.
>
>    Make it configurable?
Oh, yes. Sorry for the expression.
0xffffffff81000000 cannot be used on Loongson64 if CONFIG_RANDOMIZE_BASE 
is disabled.
It's lower than address of _end. It makes relocation_addr_valid() return 
0 always.

Thanks!
Jinyang

>> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
> [...]
>
> MBR, Sergei

Re: [PATCH 3/3] MIPS: KASLR: Make relocation_address can be configured

[Thomas Bogendoerfer]

On Thu, Nov 19, 2020 at 10:29:14AM +0800, Jinyang He wrote:
> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
> always returns a constant. It is not friendly to users if the address
> cannot be used. Make it can be configured at Kconfig.

and how do I get the information which address I need to enter ?
This looks more like platforms need to supply a working address and
not the user configuring the kernel...

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH 3/3] MIPS: KASLR: Make relocation_address can be configured

[Jinyang He]

Hi,

On 11/19/2020 08:45 PM, Thomas Bogendoerfer wrote:
> On Thu, Nov 19, 2020 at 10:29:14AM +0800, Jinyang He wrote:
>> When CONFIG_RANDOMIZE_BASE is not set, determine_relocation_address()
>> always returns a constant. It is not friendly to users if the address
>> cannot be used. Make it can be configured at Kconfig.
> and how do I get the information which address I need to enter ?
> This looks more like platforms need to supply a working address and
> not the user configuring the kernel...
You are right.

We only have two address to enter if CONFIG_RANDOMIZE_BASE disabled. One
is 0xffffffff81000000 in the current if succeed, the other is the orignal
address if failed. From relocation_addr_valid() we see that the avaliable
address need to higher than &_end to avoid overlaps original kernel.
E.g. 0xffffffff83000000 and 0xffffffff84000000 both is avaliable on
Loongson64 platform when &_end ==  0xffffffff82213f80. But
0xffffffff82000000 is not available in that case.

In reality test, I compiled kernel first and got &_end. And then modified
the relocate_address to avaliable and compiled kernel once more. It is
a bad idea.

Is it different from modifying CONFIG_PHYSICAL_START when just relocate
one address? Does it make sense if only one address to relocate?

Morever, RANDOMIZE_BASE is normally avaliable. Can we add a kernel
parameter like "relocation=0xffffffff81000000" to direct address?
At least, other architecture disabling RANDOMIZE_BASE looks like "nokaslr".
Thus, can we delete these code which RANDOMIZE_BASE disabled?

Thanks! :-)
Jinyang

> Thomas.
>

Re: [PATCH 1/3] MIPS: KASLR: Correcte valid bits in apply_r_mips_26_rel

[Thomas Bogendoerfer]

On Thu, Nov 19, 2020 at 10:29:12AM +0800, Jinyang He wrote:
> Apply_r_mips_26_rel() relocates instructions like j, jal and etc. These
> instructions consist of 6bits function field and 26bits address field.
> The value of target_addr as follows,
> =================================================================
> |     high 4bits           |            low 28bits              |
> =================================================================
> |the high 4bits of this PC | the low 26bits of instructions << 2|
> =================================================================
> Thus, loc_orig and log_new both need high 4bits ranther than high 6bits.
						  rather

> Replace 0x3ffffff with 0xfffffff.
> 
> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
> ---
>  arch/mips/kernel/relocate.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
> index 3d80a51..709cfa0 100644
> --- a/arch/mips/kernel/relocate.c
> +++ b/arch/mips/kernel/relocate.c
> @@ -95,7 +95,7 @@ static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
>  
>  	/* Original target address */
>  	target_addr <<= 2;
> -	target_addr += (unsigned long)loc_orig & ~0x03ffffff;
> +	target_addr += (unsigned long)loc_orig & ~0x0fffffff;

how about using 

	target_addr += (unsigned long)log_orig & 0xf0000000;

which makes it IMHO even clearer what this does ?

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]

Re: [PATCH 1/3] MIPS: KASLR: Correcte valid bits in apply_r_mips_26_rel

[Jinyang He]

Hi,

On 11/19/2020 08:36 PM, Thomas Bogendoerfer wrote:
> On Thu, Nov 19, 2020 at 10:29:12AM +0800, Jinyang He wrote:
>> Apply_r_mips_26_rel() relocates instructions like j, jal and etc. These
>> instructions consist of 6bits function field and 26bits address field.
>> The value of target_addr as follows,
>> =================================================================
>> |     high 4bits           |            low 28bits              |
>> =================================================================
>> |the high 4bits of this PC | the low 26bits of instructions << 2|
>> =================================================================
>> Thus, loc_orig and log_new both need high 4bits ranther than high 6bits.
> 						  rather
>
>> Replace 0x3ffffff with 0xfffffff.
>>
>> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
>> ---
>>   arch/mips/kernel/relocate.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
>> index 3d80a51..709cfa0 100644
>> --- a/arch/mips/kernel/relocate.c
>> +++ b/arch/mips/kernel/relocate.c
>> @@ -95,7 +95,7 @@ static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
>>   
>>   	/* Original target address */
>>   	target_addr <<= 2;
>> -	target_addr += (unsigned long)loc_orig & ~0x03ffffff;
>> +	target_addr += (unsigned long)loc_orig & ~0x0fffffff;
> how about using
>
> 	target_addr += (unsigned long)log_orig & 0xf0000000;
>
> which makes it IMHO even clearer what this does ?
That sounds good. I'll send v2 later.

Thanks,
Jinyang.

> Thomas.
>