On Mon, Aug 24, 2020 at 11:50 PM Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote: > > Hi Alexei, > > On Mon, 24 Aug 2020 20:27:28 -0700 Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote: > > > > I didn't receive the first email you've replied to. > > The build error is: > > " > > No libelf found > > make[5]: *** [Makefile:284: elfdep] Error 1 > > " > > and build process stops because libelf is not found, right? > > That is expected and necessary. > > bpf_preload needs libbpf that depends on libelf. > > The only 'fix' is to turn off bpf_preload. > > It's off by default. > > allmodconfig cannot build bpf_preload umd if there is no libelf. > > There is CC_CAN_LINK that does feature detection. > > We can extend scripts/cc-can-link.sh or add another script that > > will do CC_CAN_LINK_LIBELF, but such approach doesn't scale. > > imo it's cleaner to rely on feature detection by libbpf Makefile with > > an error above instead of adding such knobs to top Kconfig. > > Does it make sense? > > Sorry, but if this is not necessary to build the kernel, then an > allmodconfig build needs to succeed so you need to do the detection and > turn it off automatically. Or you could make it so that it has to be > manually enabled in all circumstances. what do you suggest to use to make it 'manually enabled' ? All I could think of is to add: depends on !COMPILE_TEST so that allmodconfig doesn't pick it up.
