On Mon, Apr 03, 2023 at 08:20:38AM +0300, Péter Ujfalusi wrote: > > > On 01/04/2023 10:44, Dan Carpenter wrote: > > On Fri, Mar 31, 2023 at 10:14:11AM +0300, Péter Ujfalusi wrote: > >> if src_fw_module is NULL then the print will be: > >> source (efault) or sink sink.module.name widget weren't set up properly > >> > >> Guennadi is relying on some black magic in the printk system to handle > >> the printing instead of open coding. > > > > I've done compiler related work and explored some weird aspect of the > > C language and I am so fascinated by this. I would have thought it > > crashes before the function is called. I cannot even imagine how black > > magic like this would work. > > I think it is not a compiler magic, but kernel magic: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/vsprintf.c#n700 > > > Is there anyway I can test this? > > You could, If you have a laptop which uses SOF and it is Intel 11th gen > or newer then you can switch it to IPC4 and install the opt-in v2.5 > (which would need with 6.4 kernel). > Apply this patch to 6.3-rc (or 6.2) and boot up, but unpatched kernel > will NULL dereference, so you need to have a backup option. > > https://github.com/thesofproject/sof-bin > > The v2.5 is not there as a release,you need to fetch the repo and follow > the instructions. > > Read the instruction in v2.5.x/README.md before attempting to use this > release. > > Now that I look back at the patch, yes it is not obvious, but it is > doing a valid thing. Yeah. Fine. It doesn't crash but "valid" is kind of debatable. It's a super ugly thing. regards, dan carpenter
