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SubjectRe: [PATCH] LoongArch: Add kernel address sanitizer support
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Hi, Ruoyao

On 2023/3/28 下午7:39, Xi Ruoyao wrote:
> On Tue, 2023-03-28 at 19:17 +0800, Qing Zhang wrote:
>
> /* snip */
>
>
>> -void * __init relocate_kernel(void)
>> +unsigned long __init relocate_kernel(void)
>
> Why we must modify relocate_kernel for KASAN?

When the CONFIG_RANDOMIZE_BASE is enabled, the kernel will be updated to
a random new address.
Kasan needs to call kasan_early_init before start_kernel.
There are two situations:
1> After enabling CONFIG_RELOCATABLE, call kasan_early_init.
2> After CONFIG_RELOCATABLE is not enabled, call kasan_early_init.

In order to prevent code redundancy and semantic problems caused by
calling kasan_early_init (before jr a0) at the old PC.

Thanks,
-Qing
>
>>  {
>>         unsigned long kernel_length;
>>         unsigned long random_offset = 0;
>>         void *location_new = _text; /* Default to original kernel start */
>> -       void *kernel_entry = start_kernel; /* Default to original kernel entry point */
>>         char *cmdline = early_ioremap(fw_arg1, COMMAND_LINE_SIZE); /* Boot command line is passed in fw_arg1 */
>>
>>         strscpy(boot_command_line, cmdline, COMMAND_LINE_SIZE);
>> @@ -190,9 +189,6 @@ void * __init relocate_kernel(void)
>>
>>                 reloc_offset += random_offset;
>>
>> -               /* Return the new kernel's entry point */
>> -               kernel_entry = RELOCATED_KASLR(start_kernel);
>> -
>>                 /* The current thread is now within the relocated kernel */
>>                 __current_thread_info = RELOCATED_KASLR(__current_thread_info);
>>
>> @@ -204,7 +200,7 @@ void * __init relocate_kernel(void)
>>
>>         relocate_absolute(random_offset);
>>
>> -       return kernel_entry;
>> +       return random_offset;
>

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