On Wed, 2022-10-12 at 05:37 +0000, Song Liu wrote: > > Then you have code that operates on module text like: > > if (is_vmalloc_or_module_addr(addr)) > > pfn = vmalloc_to_pfn(addr); > > > > It looks like it would work (on x86 at least). Should it be > > expected > > to? > > > > Especially after this patch, where there is memory that isn't even > > tracked by the original vmap_area trees, it is pretty much a > > separate > > allocator. So I think it might be nice to spell out which other > > vmalloc > > APIs work with these new functions since they are named "vmalloc". > > Maybe just say none of them do. > > I guess it is fair to call this a separate allocator. Maybe > vmalloc_exec is not the right name? I do think this is the best > way to build an allocator with vmap tree logic. Yea, I don't know about the name. I think someone else suggested it specifically, right? I had called mine perm_alloc() so it could also handle read-only and other permissions. If you keep vmalloc_exec() it needs some big comments about which APIs can work with it, and an audit of the existing code that works on module and JIT text. > > > > > > > Separate from that, I guess you are planning to make this limited > > to > > certain architectures? It might be better to put logic with > > assumptions > > about x86 boot time page table details inside arch/x86 somewhere. > > Yes, the architecture need some text_poke mechanism to use this. It also depends on the space between _etext and the PMD aligned _etext to be present and not get used by anything else. For other architectures, there might be rodata there or other things. > On BPF side, x86_64 calls this directly from arch code (jit engine), > so it is mostly covered. For modules, we need to handle this better. That old RFC has some ideas around this. I kind of like your incremental approach though. To me it seems to be moving in the right direction.
