On Feb 1, 2023, at 11:23 PM, Christophe Leroy [off-list ref] wrote:



Le 01/02/2023 à 23:32, Song Liu a écrit :

quoted

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_TEXT,
        MOD_DATA,
        MOD_RODATA,
        MOD_RO_AFTER_INIT,
        MOD_INIT_TEXT,
        MOD_INIT_DATA,
        MOD_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@kernel.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Thomas Gleixner <redacted>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Christophe Leroy <redacted>

  CALL    scripts/checksyscalls.sh
  CC      kernel/module/main.o
kernel/module/main.c: In function 'mod_mem_use_vmalloc':
kernel/module/main.c:1175:16: error: implicit declaration of function 
'mod_mem_is_core_data'; did you mean 'mod_mem_type_is_core_data'? 
[-Werror=implicit-function-declaration]
 1175 |         return mod_mem_is_core_data(type);
      |                ^~~~~~~~~~~~~~~~~~~~
      |                mod_mem_type_is_core_data
cc1: some warnings being treated as errors
make[3]: *** [scripts/Makefile.build:252: kernel/module/main.o] Error 1
make[2]: *** [scripts/Makefile.build:504: kernel/module] Error 2
make[1]: *** [scripts/Makefile.build:504: kernel] Error 2
make: *** [Makefile:2024: .] Error 2

Oops..  

Let me get this through build tests by kernel test bot.

Thanks,
Song