Re: livepatching tree for linux-next

From: Andrew Morton
Date: Wed Jan 07 2015 - 18:30:14 EST


On Thu, 8 Jan 2015 00:01:02 +0100 (CET) Jiri Kosina <jkosina@xxxxxxx> wrote:

> On Wed, 7 Jan 2015, Andrew Morton wrote:
>
> > > OK, I have added this from today
> >
> > My x86_64 allmodconfig broke.
> >
> > In file included from include/linux/livepatch.h:29,
> > from kernel/livepatch/core.c:30:
> > ./arch/x86/include/asm/livepatch.h:29:2: error: #error Your compiler must support -mfentry for live patching to work
>
> [ adding Steven and Masami to CC, as this in some sense is related in
> both to ftrace regs caller, and to IPMODIFY users in general ]
>
> Well, if your gcc is too old (which is a fact detemined during build time,
> so there is no way to express this in Kconfig language in form of
> dependencies), we have to introduce build-time failure, as there is no way
> for this to work on compilers that don't support fentry on x86_64.
>
> The only remaining option is to let the code build, pretend that
> everything is working, but do something like
>
> #ifndef CC_USING_FENTRY
> printk("The compiler you used to compile your kernel was ancient "
> "there is no way for you to make use of this feature\n");
> return -EINVAL;
> #endif
>
> or so ... which I personally detest even more.

um, what's so special about this patchset that it gets to be the first
code in the history of the kernel which breaks allmodconfig?

Please find a way to fix it. Copying CONFIG_CC_STACKPROTECTOR is one way.

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