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. 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. -- Cheers, Petr
