[PATCH v2 1/2] MIPS: relocatable: Provide kaslr_offset() to get the kernel offset

[PATCH v2 1/2] MIPS: relocatable: Provide kaslr_offset() to get the kernel offset

[Jinyang He]

Provide kaslr_offset() to get the kernel offset when KASLR is enabled.
Error may occur before update_kaslr_offset(), so put it at the end of
the offset branch.

Fixes: a307a4ce9ecd ("MIPS: Loongson64: Add KASLR support")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
---
 arch/mips/include/asm/page.h |  6 ++++++
 arch/mips/kernel/relocate.c  | 10 ++++++++++
 arch/mips/kernel/setup.c     |  3 +++
 3 files changed, 19 insertions(+)

diff --git a/arch/mips/include/asm/page.h b/arch/mips/include/asm/page.h
index 6a77bc4..74082e3 100644
--- a/arch/mips/include/asm/page.h
+++ b/arch/mips/include/asm/page.h
@@ -255,6 +255,12 @@ extern bool __virt_addr_valid(const volatile void *kaddr);
 
 #define VM_DATA_DEFAULT_FLAGS	VM_DATA_FLAGS_TSK_EXEC
 
+extern unsigned long __kaslr_offset;
+static inline unsigned long kaslr_offset(void)
+{
+	return __kaslr_offset;
+}
+
 #include <asm-generic/memory_model.h>
 #include <asm-generic/getorder.h>
 
diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
index c643c81..95abb9c 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -300,6 +300,13 @@ static inline int __init relocation_addr_valid(void *loc_new)
 	return 1;
 }
 
+static inline void __init update_kaslr_offset(unsigned long *addr, long offset)
+{
+	unsigned long *new_addr = (unsigned long *)RELOCATED(addr);
+
+	*new_addr = (unsigned long)offset;
+}
+
 #if defined(CONFIG_USE_OF)
 void __weak *plat_get_fdt(void)
 {
@@ -410,6 +417,9 @@ void *__init relocate_kernel(void)
 
 		/* Return the new kernel's entry point */
 		kernel_entry = RELOCATED(start_kernel);
+
+		/* Error may occur before, so keep it at last */
+		update_kaslr_offset(&__kaslr_offset, offset);
 	}
 out:
 	return kernel_entry;
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 7e1f8e2..31ba343 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -84,6 +84,9 @@ static struct resource code_resource = { .name = "Kernel code", };
 static struct resource data_resource = { .name = "Kernel data", };
 static struct resource bss_resource = { .name = "Kernel bss", };
 
+unsigned long __kaslr_offset __ro_after_init;
+EXPORT_SYMBOL(__kaslr_offset);
+
 static void *detect_magic __initdata = detect_memory_region;
 
 #ifdef CONFIG_MIPS_AUTO_PFN_OFFSET
-- 
2.1.0

[PATCH v2 2/2] MIPS: relocatable: Use __kaslr_offset in show_kernel_relocation

[Jinyang He]

The type of the VMLINUX_LOAD_ADDRESS macro is the (unsigned long long)
in 32bits kernel but (unsigned long) in the 64-bit kernel. Although there
is no error here, avoid using it to calculate kaslr_offset. And here we
may need is that the address of __kaslr_offset rather than (void *)offset.

Signed-off-by: Jinyang He <hejinyang@loongson.cn>
---
 arch/mips/kernel/relocate.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
index 95abb9c..52018a3 100644
--- a/arch/mips/kernel/relocate.c
+++ b/arch/mips/kernel/relocate.c
@@ -430,13 +430,9 @@ void *__init relocate_kernel(void)
  */
 static void show_kernel_relocation(const char *level)
 {
-	unsigned long offset;
-
-	offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS);
-
-	if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) {
+	if (__kaslr_offset > 0) {
 		printk(level);
-		pr_cont("Kernel relocated by 0x%pK\n", (void *)offset);
+		pr_cont("Kernel relocated by 0x%pK\n", &__kaslr_offset);
 		pr_cont(" .text @ 0x%pK\n", _text);
 		pr_cont(" .data @ 0x%pK\n", _sdata);
 		pr_cont(" .bss  @ 0x%pK\n", __bss_start);
-- 
2.1.0

Re: [PATCH v2 2/2] MIPS: relocatable: Use __kaslr_offset in show_kernel_relocation

[Thomas Bogendoerfer]

On Wed, Feb 03, 2021 at 06:35:10PM +0800, Jinyang He wrote:
> The type of the VMLINUX_LOAD_ADDRESS macro is the (unsigned long long)
> in 32bits kernel but (unsigned long) in the 64-bit kernel. Although there
> is no error here, avoid using it to calculate kaslr_offset. And here we
> may need is that the address of __kaslr_offset rather than (void *)offset.
> 
> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
> ---
>  arch/mips/kernel/relocate.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
> index 95abb9c..52018a3 100644
> --- a/arch/mips/kernel/relocate.c
> +++ b/arch/mips/kernel/relocate.c
> @@ -430,13 +430,9 @@ void *__init relocate_kernel(void)
>   */
>  static void show_kernel_relocation(const char *level)
>  {
> -	unsigned long offset;
> -
> -	offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS);
> -
> -	if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) {
> +	if (__kaslr_offset > 0) {
>  		printk(level);
> -		pr_cont("Kernel relocated by 0x%pK\n", (void *)offset);
> +		pr_cont("Kernel relocated by 0x%pK\n", &__kaslr_offset);

are you sure ? I would have expected (void *)__kaslr_offset here.

Thomas.

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

Re: [PATCH v2 2/2] MIPS: relocatable: Use __kaslr_offset in show_kernel_relocation

[Jinyang He]

On 02/04/2021 11:36 PM, Thomas Bogendoerfer wrote:

> On Wed, Feb 03, 2021 at 06:35:10PM +0800, Jinyang He wrote:
>> The type of the VMLINUX_LOAD_ADDRESS macro is the (unsigned long long)
>> in 32bits kernel but (unsigned long) in the 64-bit kernel. Although there
>> is no error here, avoid using it to calculate kaslr_offset. And here we
>> may need is that the address of __kaslr_offset rather than (void *)offset.
>>
>> Signed-off-by: Jinyang He <hejinyang@loongson.cn>
>> ---
>>   arch/mips/kernel/relocate.c | 8 ++------
>>   1 file changed, 2 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c
>> index 95abb9c..52018a3 100644
>> --- a/arch/mips/kernel/relocate.c
>> +++ b/arch/mips/kernel/relocate.c
>> @@ -430,13 +430,9 @@ void *__init relocate_kernel(void)
>>    */
>>   static void show_kernel_relocation(const char *level)
>>   {
>> -	unsigned long offset;
>> -
>> -	offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS);
>> -
>> -	if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) {
>> +	if (__kaslr_offset > 0) {
>>   		printk(level);
>> -		pr_cont("Kernel relocated by 0x%pK\n", (void *)offset);
>> +		pr_cont("Kernel relocated by 0x%pK\n", &__kaslr_offset);
> are you sure ? I would have expected (void *)__kaslr_offset here.
>
> Thomas.
>
It is my fault. I misunderstood the meaning of 'by' and '@' because of
my poor English. Thank you for pointing out my fault. I'll send v3 later.

Thanks,
Jinyang