linux-kernel - Re: [PATCH v3 2/5] alloc_tag: load module tags into separate contiguous memory

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Message-ID: <CAJuCfpETusPzdjEg01zahF7NOStQJZmoM5Jabqd5tJpCCQrj2g@mail.gmail.com>
Date: Mon, 14 Oct 2024 19:10:56 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: kent.overstreet@...ux.dev, corbet@....net, arnd@...db.de, 
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Subject: Re: [PATCH v3 2/5] alloc_tag: load module tags into separate
 contiguous memory

On Mon, Oct 14, 2024 at 4:51 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Mon, 14 Oct 2024 13:36:43 -0700 Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> > When a module gets unloaded there is a possibility that some of the
> > allocations it made are still used and therefore the allocation tags
> > corresponding to these allocations are still referenced. As such, the
> > memory for these tags can't be freed. This is currently handled as an
> > abnormal situation and module's data section is not being unloaded.
> > To handle this situation without keeping module's data in memory,
> > allow codetags with longer lifespan than the module to be loaded into
> > their own separate memory. The in-use memory areas and gaps after
> > module unloading in this separate memory are tracked using maple trees.
> > Allocation tags arrange their separate memory so that it is virtually
> > contiguous and that will allow simple allocation tag indexing later on
> > in this patchset. The size of this virtually contiguous memory is set
> > to store up to 100000 allocation tags.
> >
> > ...
> >
> > --- a/kernel/module/main.c
> > +++ b/kernel/module/main.c
> > @@ -1254,22 +1254,17 @@ static int module_memory_alloc(struct module *mod, enum mod_mem_type type)
> >       return 0;
> >  }
> >
> > -static void module_memory_free(struct module *mod, enum mod_mem_type type,
> > -                            bool unload_codetags)
> > +static void module_memory_free(struct module *mod, enum mod_mem_type type)
> >  {
> >       struct module_memory *mem = &mod->mem[type];
> > -     void *ptr = mem->base;
> >
> >       if (mem->is_rox)
> >               vfree(mem->rw_copy);
> >
> > -     if (!unload_codetags && mod_mem_type_is_core_data(type))
> > -             return;
> > -
> > -     execmem_free(ptr);
> > +     execmem_free(mem->base);
> >  }
>
> The changes around here are dependent upon Mike's "module: make
> module_memory_{alloc,free} more self-contained", which is no longer in
> mm-unstable.  I assume Mike is working on a v2 so I'll park this series
> for now.

Looks like the last update on Mike's patchset was back in May. Let me
check with Mike if he is planning to get it out soon. I would like my
patchset to get into 6.12 if possible.
Thanks,
Suren.