linux-kernel - Re: [PATCH v2 2/2] MIPS: relocatable: Use __kaslr_offset in show_kernel

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Message-ID: <a2f9868c-707c-6f63-e5e4-956354d241e4@loongson.cn>
Date:   Fri, 5 Feb 2021 09:55:01 +0800
From:   Jinyang He <hejinyang@...ngson.cn>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Huacai Chen <chenhuacai@...nel.org>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] MIPS: relocatable: Use __kaslr_offset in
 show_kernel_relocation

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@...ngson.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