Re: [PATCH] Documentation/ABI: Document the non-ABI status ofKconfig and symbols
From: Josh Triplett
Date: Thu Oct 24 2013 - 05:08:41 EST
On Thu, Oct 24, 2013 at 10:57:11AM +0200, Richard Weinberger wrote:
> On Thu, Oct 24, 2013 at 10:41 AM, Josh Triplett <josh@xxxxxxxxxxxxxxxx> wrote:
> > Discussion at Kernel Summit made it clear that the presence or absence
> > of specific Kconfig symbols are not considered ABI, and that no
> > userspace (or bootloader, etc) should rely on them.
> > In addition, kernel-internal symbols are well established as non-ABI,
> > per Documentation/stable_api_nonsense.txt.
> > Document both of these in Documentation/ABI/README, in a new section for
> > notable bits of non-ABI.
> > Signed-off-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
> > ---
> > Documentation/ABI/README | 13 +++++++++++++
> > 1 file changed, 13 insertions(+)
> > diff --git a/Documentation/ABI/README b/Documentation/ABI/README
> > index 1006982..1fafc4b 100644
> > --- a/Documentation/ABI/README
> > +++ b/Documentation/ABI/README
> > @@ -72,3 +72,16 @@ kernel tree without going through the obsolete state first.
> > It's up to the developer to place their interfaces in the category they
> > wish for it to start out in.
> > +
> > +
> > +Notable bits of non-ABI, which should not under any circumstances be considered
> > +stable:
> > +
> > +- Kconfig. Userspace should not rely on the presence or absence of any
> > + particular Kconfig symbol, in /proc/config.gz, in the copy of .config
> > + commonly installed to /boot, or in any invocation of the kernel build
> > + process.
> > +
> > +- Kernel-internal symbols. Do not rely on the presence, absence, location, or
> > + type of any kernel symbol, either in System.map files or the kernel binary
> > + itself. See Documentation/stable_api_nonsense.txt.
> And what about the kernel make "interface", is it considered also as non-ABI?
> Before ffee0de (x86: Default to ARCH=x86 to avoid overriding CONFIG_64BIT)
> "make defconfig ARCH=x86" produced a i386 defconfig. Now it produces a
> x86_64 defconfig.
> I'm sure some build scripted failed badly.
I seriously considered including that, but I could imagine that some
parts of that interface might be considered more stable than others (the
names of targets, for instance), and I wanted to stick to completely
uncontroversial items. If there's consensus that part or all of the
invocation of "make" to build the kernel is non-ABI, we can easily
enough add that to the non-ABI list, but let's start with Kconfig and
- Josh Triplett
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