Re: [PATCH v2 06/10] module: introduce MODULE_STATE_GONE

[Petr Pavlu]

On 1/21/25 10:57, Mike Rapoport wrote:
> In order to use execmem's API for temporal remapping of the memory
> allocated from ROX cache as writable, there is a need to distinguish
> between the state when the module is being formed and the state when it is
> deconstructed and freed so that when module_memory_free() is called from
> error paths during module loading it could restore ROX mappings.
> 
> Replace open coded checks for MODULE_STATE_UNFORMED with a helper
> function module_is_formed() and add a new MODULE_STATE_GONE that will be
> set when the module is deconstructed and freed.

I don't fully follow why this case requires a new module state. My
understanding it that the function load_module() has the necessary
context that after calling layout_and_allocate(), the updated ROX
mappings need to be restored. I would then expect the function to be
appropriately able to unwind this operation in case of an error. It
could be done by having a helper that walks the mappings and calls
execmem_restore_rox(), or if you want to keep it in module_memory_free()
as done in the patch #7 then a flag could be passed down to
module_deallocate() -> free_mod_mem() -> module_memory_free()?

It is at least good that MODULE_STATE_GONE is only set in free_module()
past the sysfs teardown, so it never shows in
/sys/module/<mod>/initstate. Otherwise, this would require teaching kmod
about this state as well.

-- 
Thanks,
Petr