Re: [PATCH v8] module: replace module_layout with module_memory

Song Liu
2023-02-02T19:49:21Z

> On Feb 1, 2023, at 11:23 PM, Christophe Leroy <christophe.leroy@csgroup.eu> wrote:
>
>
>
> Le 01/02/2023 à 23:32, 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_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 <tglx@linutronix.de>
>> Cc: Peter Zijlstra <peterz@infradead.org>
>> Cc: Guenter Roeck <linux@roeck-us.net>
>> Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
>>
>
> 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