On Mon, Aug 19, 2024 at 08:15:07AM -0700, Suren Baghdasaryan 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 and max_module_alloc_tags kernel
> parameter is introduced to change this size.
>
> Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> ---
> .../admin-guide/kernel-parameters.txt | 4 +
> include/asm-generic/codetag.lds.h | 19 ++
> include/linux/alloc_tag.h | 13 +-
> include/linux/codetag.h | 35 ++-
> kernel/module/main.c | 67 +++--
> lib/alloc_tag.c | 245 ++++++++++++++++--
> lib/codetag.c | 101 +++++++-
> scripts/module.lds.S | 5 +-
> 8 files changed, 429 insertions(+), 60 deletions(-)
...
> diff --git a/include/linux/codetag.h b/include/linux/codetag.h
> index c2a579ccd455..c4a3dd60205e 100644
> --- a/include/linux/codetag.h
> +++ b/include/linux/codetag.h
> @@ -35,8 +35,13 @@ struct codetag_type_desc {
> size_t tag_size;
> void (*module_load)(struct codetag_type *cttype,
> struct codetag_module *cmod);
> - bool (*module_unload)(struct codetag_type *cttype,
> + void (*module_unload)(struct codetag_type *cttype,
> struct codetag_module *cmod);
> + void (*module_replaced)(struct module *mod, struct module *new_mod);
> + bool (*needs_section_mem)(struct module *mod, unsigned long size);
> + void *(*alloc_section_mem)(struct module *mod, unsigned long size,
> + unsigned int prepend, unsigned long align);
> + void (*free_section_mem)(struct module *mod, bool unused);
> };
>
> struct codetag_iterator {
> @@ -71,11 +76,31 @@ struct codetag_type *
> codetag_register_type(const struct codetag_type_desc *desc);
>
> #if defined(CONFIG_CODE_TAGGING) && defined(CONFIG_MODULES)
> +
> +bool codetag_needs_module_section(struct module *mod, const char *name,
> + unsigned long size);
> +void *codetag_alloc_module_section(struct module *mod, const char *name,
> + unsigned long size, unsigned int prepend,
> + unsigned long align);
> +void codetag_free_module_sections(struct module *mod);
> +void codetag_module_replaced(struct module *mod, struct module *new_mod);
> void codetag_load_module(struct module *mod);
> -bool codetag_unload_module(struct module *mod);
> -#else
> +void codetag_unload_module(struct module *mod);
> +
> +#else /* defined(CONFIG_CODE_TAGGING) && defined(CONFIG_MODULES) */
> +
> +static inline bool
> +codetag_needs_module_section(struct module *mod, const char *name,
> + unsigned long size) { return false; }
> +static inline void *
> +codetag_alloc_module_section(struct module *mod, const char *name,
> + unsigned long size, unsigned int prepend,
> + unsigned long align) { return NULL; }
> +static inline void codetag_free_module_sections(struct module *mod) {}
> +static inline void codetag_module_replaced(struct module *mod, struct module *new_mod) {}
> static inline void codetag_load_module(struct module *mod) {}
> -static inline bool codetag_unload_module(struct module *mod) { return true; }
> -#endif
> +static inline void codetag_unload_module(struct module *mod) {}
> +
> +#endif /* defined(CONFIG_CODE_TAGGING) && defined(CONFIG_MODULES) */
Maybe I'm missing something, but can't alloc_tag::module_unload() just copy
the tags that cannot be freed somewhere outside of module sections and then
free the module?
The heavy lifting would be localized to alloc_tags rather than spread all
over.
--
Sincerely yours,
Mike.
