On Mon, Jan 30, 2023 at 10:21:09AM -0800, Song Liu wrote: > 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. This adds slightly more entries to > mod_tree (from up to 3 entries per module, to up to 7 entries per > module). However, this at most adds a small constant overhead to > __module_address(), which is expected to be fast. > > 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. > > module_memory simplifies quite some of the module code. For example, > ARCH_WANTS_MODULES_DATA_IN_VMALLOC is a lot cleaner, as it just uses a > different allocator for the data. kernel/module/strict_rwx.c is also > much cleaner with module_memory. > > Signed-off-by: Song Liu <song@xxxxxxxxxx> > Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > Cc: Guenter Roeck <linux@xxxxxxxxxxxx> > Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx> > > --- > > This is the preparation work for the type aware module_alloc() discussed > in [1]. While this work is not covered much in the discussion, it is a > critical step of the effort. > > As this part grows pretty big (~1000 lines, + and -), I would like get > some feedback on it, so that I know it is on the right track. > > Please share your comments. Thanks! Aside from the things already reported I like where this is going.
