Re: livepatching tree for linux-next

[Jiri Kosina]

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.

-- 
Jiri Kosina
SUSE Labs
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