On Wed, Jun 19, 2024 at 01:50:36AM +0900, Masahiro Yamada wrote: > On Wed, Jun 19, 2024 at 1:44 AM Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > On Mon, Jun 17, 2024 at 05:58:19PM +0000, Sami Tolvanen wrote: > > > Hi folks, > > > > > > This series implements CONFIG_MODVERSIONS for Rust, an important > > > feature for distributions like Android that want to ship Rust > > > kernel modules, and depend on modversions to help ensure module ABI > > > compatibility. > > > > > > There have been earlier proposals [1][2] that would allow Rust > > > modules to coexist with modversions, but none that actually implement > > > symbol versioning. Unlike C, Rust source code doesn't have sufficient > > > information about the final ABI, as the compiler has considerable > > > freedom in adjusting structure layout for improved performance [3], > > > for example, which makes using a source code parser like genksyms > > > a non-starter. Based on Matt's suggestion and previous feedback > > > from maintainers, this series uses DWARF debugging information for > > > computing versions. DWARF is an established and relatively stable > > > format, which includes all the necessary ABI details, and adding a > > > CONFIG_DEBUG_INFO dependency for Rust symbol versioning seems like a > > > reasonable trade-off. > > > > > > The first 12 patches of this series add a small tool for computing > > > symbol versions from DWARF, called gendwarfksyms. When passed a list > > > of exported symbols, the tool generates an expanded type string > > > for each symbol, and computes symbol CRCs similarly to genksyms. > > > gendwarfksyms is written in C and uses libdw to process DWARF, mainly > > > because of the existing support for C host tools that use elfutils > > > (e.g., objtool). > > > > That's cool, can the C code be switched to also use this? That way we > > only have one path/code for all of this? > > > As the description says, it requires CONFIG_DEBUG_INFO. > We can strip the debug info from the final vmlinux, but > I guess the build speed will be even slower than the current genksyms. For people who want genksyms (i.e. distros), don't they normally already enable DEBUG_INFO as well? The problems of genksyms are well known and a pain (I speak from experience), so replacing it with info based on DWARF would be great, I'll gladly trade off the DEBUG_INFO issue for stablilty! thanks, greg k-h
