On 2018-09-11 15:29:02 -0700, Russ Allbery wrote: > Vincent Lefevre <vinc...@vinc17.net> writes: > > > This would mean that a breakage is possible after any patch (in > > particular with those "Update to SVN..." in the changelog). Thus this > > means that the kernel module build system must check that the GCC Debian > > package version number matches the one used to build the kernel. For > > sid, GCC is often not in sync with the one used to build the > > kernel. This is a really big problem. > > I don't think it's an NVIDIA-specific problem, though, right? Doesn't > this happen with any kernel module build?
I assume that this depends on which features of the interface are used. > Or am I confused and this is an NVIDIA-specific check? I don't know. It would be interesting to know the causes of the failures. I tried to search for information and found: https://www.kernel.org/doc/html/v4.14/process/stable-api-nonsense.html Some issues may come from the kernel build options, and concerning the compiler: "Depending on the version of the C compiler you use, different kernel data structures will contain different alignment of structures, and possibly include different functions in different ways (putting functions inline or not.) The individual function organization isn’t that important, but the different data structure padding is very important." Well, concerning the alignment of structures and internal padding, this is a much more general problem that could affect any library that expose structures in their .h public header files. I assume that this will never change, otherwise one would see a breakage in various places. So, I'm wondering why this is mentioned. Concerning inline functions, this would need explanations. In any case, I don't see why this would change between minor versions. And this is more likely to be affected by compiler options. Moreover, it appears that NVIDIA's compiler version check predates the change of numbering in GCC. See for instance: https://devtalk.nvidia.com/default/topic/833061/nvidia-drivers-352-09-dont-install/ "Compiler version check failed: The major and minor number of the compiler used to compile the kernel: gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) does not match the compiler used here: cc (Ubuntu 4.9.2-0ubuntu1~14.04) 4.9.2" In the past, GCC 4.6, 4.7, 4.8, 4.9 were indeed different releases, but now, only the major number corresponds to some given release: 5, 6, 7, 8, 9 (GCC was using X.Y.Z where Z was a patchlevel, and now uses X.Y where Y is a patchlevel, thus to be consistent with the past test, NVIDIA should now just check X). https://devtalk.nvidia.com/default/topic/960778/linux/having-trouble-with-the-340-96-driver-on-kali-linux-failing-cc-version-check/ says: "That's because the ABI (i.e. how parameters are passed, or how the stack is laid out) changes between gcc versions, especially between major version changes (here, v5's ABI is incompatible with V6's)." Thus only the *major* version matters. -- Vincent Lefèvre <vinc...@vinc17.net> - Web: <https://www.vinc17.net/> 100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/> Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
