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    SubjectRe: [PATCH/RFC] module: replace module_layout with module_memory
    On Mon, Jan 9, 2023 at 10:03 AM Christophe Leroy
    <christophe.leroy@csgroup.eu> 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?

    Thanks,
    Song

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