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

Christophe Leroy
2023-02-02T07:23:28Z

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