Re: [PATCH 00/15] Implement MODVERSIONS for Rust

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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?

thanks,

greg k-h