Messages in this thread | | | Date | Sun, 5 Jul 2020 09:30:15 -0400 | From | Sasha Levin <> | Subject | Re: [PATCH 4.19 119/131] tracing: Fix event trigger to accept redundant spaces |
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On Fri, Jul 03, 2020 at 09:21:03PM +0200, Pavel Machek wrote: > >> > > commit 6784beada631800f2c5afd567e5628c843362cee upstream. >> > > >> > > Fix the event trigger to accept redundant spaces in >> > > the trigger input. >> > > >> > > For example, these return -EINVAL >> > > >> > > echo " traceon" > events/ftrace/print/trigger >> > > echo "traceon if common_pid == 0" > events/ftrace/print/trigger >> > > echo "disable_event:kmem:kmalloc " > events/ftrace/print/trigger >> > > >> > > But these are hard to find what is wrong. >> > > >> > > To fix this issue, use skip_spaces() to remove spaces >> > > in front of actual tokens, and set NULL if there is no >> > > token. >> > >> > For the record, I'm not fan of this one. It is ABI change, not a >> > bugfix. >> > >> > Yes, it makes kernel interface "easier to use". It also changes >> > interface in the middle of stable series, and if people start relying >> > on new interface and start putting extra spaces, they'll get nasty >> > surprise when they move code to the older kernel. >> >> If an interface changes anywhere that breaks userspace, it needs to be >> not done, stable kernels are not an issue here or not. > >I'm not saying it is a regression; I'd scream way more if that was the >case. I'm saying it is nowhere near a fix. > >We really don't want userspace doing: > >> > > echo " traceon" > events/ftrace/print/trigger > >Because it does not work on older kernels. It will work on 4.19.131 >and break on 5.6.19.
Moving to an EOL kernel is very much unsupported.
-- Thanks, Sasha
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