On Mon, Jan 9, 2023 at 10:31 PM Christophe Leroy <christophe.leroy@xxxxxxxxxx> wrote: > > > > Le 09/01/2023 à 21:51, Song Liu a écrit : > > On Mon, Jan 9, 2023 at 10:24 AM Song Liu <song@xxxxxxxxxx> wrote: > >> > >> On Mon, Jan 9, 2023 at 10:03 AM Christophe Leroy > >> <christophe.leroy@xxxxxxxxxx> wrote: > >>> > >>> > >>> > >>> Le 06/01/2023 à 23:09, Song Liu a écrit : > >>>> module_layout manages different types of memory (text, data, rodata, etc.) > >>>> in one allocation, which is problematic for some reasons: > >>>> > >>>> 1. It is hard to enable CONFIG_STRICT_MODULE_RWX. > >>>> 2. It is hard to use huge pages in modules (and not break strict rwx). > >>>> 3. Many archs uses module_layout for arch-specific data, but it is not > >>>> obvious how these data are used (are they RO, RX, or RW?) > >>>> > >>>> Improve the scenario by replacing 2 (or 3) module_layout per module with > >>>> up to 7 module_memory per module: > >>>> > >>>> MOD_MEM_TYPE_TEXT, > >>>> MOD_MEM_TYPE_DATA, > >>>> MOD_MEM_TYPE_RODATA, > >>>> MOD_MEM_TYPE_RO_AFTER_INIT, > >>>> MOD_MEM_TYPE_INIT_TEXT, > >>>> MOD_MEM_TYPE_INIT_DATA, > >>>> MOD_MEM_TYPE_INIT_RODATA, > >>>> > >>>> and allocating them separately. > >>>> > >>>> Various archs use module_layout for different data. These data are put > >>>> into different module_memory based on their location in module_layout. > >>>> IOW, data that used to go with text is allocated with MOD_MEM_TYPE_TEXT; > >>>> data that used to go with data is allocated with MOD_MEM_TYPE_DATA, etc. > >>> > >>> I dislike how it looks with enums, things like > >>> mod->mod_mem[MOD_MEM_TYPE_INIT_TEXT] are odd and don't read nicely. > >>> Could we have something nicer like mod->mod_mem_init_text ? > >>> I know it will complicate your for_each_mod_mem_type() but it would look > >>> nicer. > >> > >> Hmm.. I am not sure whether we want 7 module_memory here. But if we > >> agree that it looks better like that, I am ok with it. > >> > >>> > >>> Also, can you explain how you switch from two trees to only one ? > >>> As far as I remember, the same question arised when I implemented > >>> CONFIG_ARCH_WANTS_MODULES_DATA_IN_VMALLOC, and the conclusion was that > >>> we had to keep two independant trees, so I'm a bit puzzled that you have > >>> now merged everything into a single tree. > >> > >> AFAICT, we only need __module_address() to work? So one tree is enough. > >> Did I miss something? > > > > Do you mean one tree will cause addr_[min|max] to be inaccurate? > > > > Yes at least. On powerpc you will have module text below kernel, > somewhere between 0xb0000000 and 0xcfffffff, and you will have module > data in vmalloc area, somewhere between 0xf0000000 and 0xffffffff. > > If you have only one tree, any address between 0xc0000000 and 0xefffffff > will trigger a tree search. Do we use this part of the address space and call __module_address()? If so, we can problem solve it with secondary addr_[min|max]. If we don't really use these addresses, we can probably just ignore it? Thanks, Song
