Messages in this thread |  | | Date | Mon, 9 Jul 2018 21:29:04 -0500 | | From | Josh Poimboeuf <> | | Subject | Re: [PATCH v2] objtool: move libelf detection to Kconfig from Makefile |
| |
On Tue, Jul 10, 2018 at 10:35:16AM +0900, Masahiro Yamada wrote: > Currently, users are allowed to enable STACK_VALIDATION regardless > of the compiler capability. The top-level Makefile warns or breaks > the build if it turns out that the host compiler cannot link libelf. > > Move the libelf test to Kconfig so that users can enable the feature > only when the host compiler can build the objtool. The ugly check > in the Makefile will go away. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Actually, looking at this again, I want to rescind my ack.
This patches changes the behavior in a subtle (but important) way.
Before, if I did "make defconfig", it would *always* choose the ORC unwinder. Then, if I didn't have libelf-devel, the build would fail and it would tell me what I need to install.
But now with this patch, if I do "make defconfig", the generated config actually changes based on what I happen to have installed on my build system. If I don't have libelf-devel, then it silently chooses the non-default unwinder (frame pointer).
This is a subtle difference, but IMO it's dangerous, because it will silently enable the frame pointer unwinder for the majority of new systems, even though it's not the default.
I strongly prefer the original behavior, because we really want to encourage people to use the ORC unwinder, even if that means they have to install a package to build it.
Also -- in general -- I suspect that silently changing the defaults like this will create a lot of bad surprises. The output of "make defconfig" should be predictable and not dependent on what RPMs I happen to have installed.
-- Josh
|  |