Re: [PATCH v2 3/4] xen: arm: enable stack protector feature

[Jan Beulich <jbeulich@xxxxxxxx>]

On 06.12.2024 05:46, Volodymyr Babchuk wrote:
> So, apart from already present
> 
> static always_inline void boot_stack_chk_guard_setup(void);
> 
> I did this:
> 
> /*
>  * Initial value is chosen by fair dice roll.
>  * It will be updated during boot process.
>  */
> #if BITS_PER_LONG == 32
> unsigned long __ro_after_init __stack_chk_guard = 0xdd2cc927;

At least this and ...

> #else
> unsigned long __ro_after_init __stack_chk_guard = 0x2d853605a4d9a09c;
> #endif
> 
> /* This function should be called from ASM only */
> void __init asmlinkage boot_stack_chk_guard_setup_early(void)
> {
>     /*
>      * Linear congruent generator. Constant is taken from
>      * Tables Of Linear Congruential Generators
>      * Of Different Sizes And Good Lattice Structure by Pierre L’Ecuyer
>      */
> #if BITS_PER_LONG == 32
>     const unsigned long a = 2891336453;

... this will need a UL suffix for Misra. Probably best to add UL on all
four constants.

As to the comment, please adhere to ./CODING_STYLE.

> #else
>     const unsigned long a = 2862933555777941757;
> #endif
>     const unsigned c = 1;

I'm having a hard time seeing why this need to be a static variable. Its
sole use is ...

>     unsigned long cycles = get_cycles();
> 
>     if ( !cycles )
>         return;
> 
>     __stack_chk_guard = cycles * a + c;

... here, where you can as well write a literal 1.

Jan