Re: [PATCH 1/4] mm: abstract initial stack setup to mm subsystem

[David Hildenbrand <david@redhat.com>]

On 24.04.25 23:15, Lorenzo Stoakes wrote:
> There are peculiarities within the kernel where what is very clearly mm
> code is performed elsewhere arbitrarily.
> 
> This violates separation of concerns and makes it harder to refactor code
> to make changes to how fundamental initialisation and operation of mm logic
> is performed.
> 
> One such case is the creation of the VMA containing the initial stack upon
> execve()'ing a new process. This is currently performed in __bprm_mm_init()
> in fs/exec.c.
> 
> Abstract this operation to create_init_stack_vma(). This allows us to limit
> use of vma allocation and free code to fork and mm only.
> 
> We previously did the same for the step at which we relocate the initial
> stack VMA downwards via relocate_vma_down(), now we move the initial VMA
> establishment too.
> 
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> ---
...

> +/*
> + * Establish the stack VMA in an execve'd process, located temporarily at the
> + * maximum stack address provided by the architecture.
> + *
> + * We later relocate this downwards in relocate_vma_down().
> + *
> + * This function is almost certainly NOT what you want for anything other than
> + * early executable initialisation.
> + *
> + * On success, returns 0 and sets *vmap to the stack VMA and *top_mem_p to the
> + * maximum addressable location in the stack (that is capable of storing a
> + * system word of data).
> + *
> + * on failure, returns an error code.
> + */

I was about to say, if you already write that much documentation, why 
not turn it into kerneldoc? :) But this function is clearly not intended 
to have more than one caller, so ... :)

Acked-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb