Re: [PATCH] LoongArch: Add kernel address sanitizer support

[Qing Zhang]

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;