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

Suren Baghdasaryan
2024-10-15T02:11:08Z

On Mon, Oct 14, 2024 at 4:51 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Mon, 14 Oct 2024 13:36:43 -0700 Suren Baghdasaryan <surenb@google.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.