Hi Petr, On Wed, Mar 12, 2025 at 5:05 AM Petr Pavlu <petr.pavlu@xxxxxxxx> wrote: > > On 3/7/25 01:12, Sami Tolvanen wrote: > > On Thu, Mar 06, 2025 at 06:28:58PM +0100, Christophe Leroy wrote: > >> Le 06/03/2025 à 14:13, Petr Pavlu a écrit : > >>> Section .static_call_sites holds data structures that need to be sorted and > >>> processed only at module load time. This initial processing happens in > >>> static_call_add_module(), which is invoked as a callback to the > >>> MODULE_STATE_COMING notification from prepare_coming_module(). > >>> > >>> The section is never modified afterwards. Make it therefore read-only after > >>> module initialization to avoid any (non-)accidental modifications. > >> > >> Maybe this suggestion is stupid, I didn't investigate the feasability but: > >> why don't we group everything that is ro_after_init in a single section just > >> like we do in vmlinux ? That would avoid having to add every new possible > >> section in the C code. > >> > >> Like we have in asm-generic/vmlinux.lds.h: > >> > >> #define RO_AFTER_INIT_DATA \ > >> . = ALIGN(8); \ > >> __start_ro_after_init = .; \ > >> *(.data..ro_after_init) \ > >> JUMP_TABLE_DATA \ > >> STATIC_CALL_DATA \ > >> __end_ro_after_init = .; > > > > I like this idea. Grouping the sections in the module linker script > > feels cleaner than having an array of section names in the code. To be > > fair, I think this code predates v5.10, where scripts/module.lds.S was > > first added. > > I agree in principle. I like that the information about ro_after_init > sections for vmlinux and modules would be in the same source form, in > linker scripts. This could eventually allow us to share the definition > of ro_after_init sections between vmlinux and modules. > > The problem is however how to find the location of the __jump_table and > static_call_sites data. In vmlinux, as a final binary, they are > annotated with start and end symbols. In modules, as relocatable files, > the approach is to rely on them being separate sections, see function > find_module_sections(). > > I could add start+end symbols for __jump_table and static_call_sites > data in scripts/module.lds.S and use them by the module loader, but this > would create an inconsistency in how various data is looked up. That's a fair point. Perhaps it makes sense to keep these sections separate for consistency, and look into cleaning this up later if needed. > Another problem is that I can't find a way to tell the linker to add these > symbols only if the specific data is actually present. You can use the preprocessor to add the symbols only if the relevant kernel config is present, similarly to how STATIC_CALL_DATA is defined in include/asm-generic/vmlinux.lds.h. In any case, the code looks correct to me. For the series: Reviewed-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx> Sami
