Fāng-ruì Sòng
unread,Oct 21, 2020, 4:32:21 PM10/21/20Sign in to reply to author
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to Kees Cook, Ingo Molnar, Stephen Rothwell, Nick Desaulniers, Arnd Bergmann, clang-built-linux, linux-arch, LKML, X86 ML
On Wed, Oct 21, 2020 at 1:09 PM Kees Cook <
kees...@chromium.org> wrote:
>
> On Wed, Oct 14, 2020 at 09:53:39PM -0700, Fāng-ruì Sòng wrote:
> > On Wed, Oct 14, 2020 at 4:04 PM Kees Cook <
kees...@chromium.org> wrote:
> > > > index 5430febd34be..b83c00c63997 100644
> > > > --- a/include/asm-generic/vmlinux.lds.h
> > > > +++ b/include/asm-generic/vmlinux.lds.h
> > > > @@ -684,6 +684,7 @@
> > > > #ifdef CONFIG_CONSTRUCTORS
> > > > #define KERNEL_CTORS() . = ALIGN(8); \
> > > > __ctors_start = .; \
> > > > + KEEP(*(SORT(.ctors.*))) \
> > > > KEEP(*(.ctors)) \
> > > > KEEP(*(SORT(.init_array.*))) \
> > > > KEEP(*(.init_array)) \
> > > > --
> > > > 2.25.1
> >
> > I think it would be great to figure out why these .ctors.* .dtors.* are generated.
>
> I haven't had the time to investigate. This patch keeps sfr's builds
> from regressing, so we need at least this first.
We need to know under what circumstances .ctors.* are generated.
For Clang>=10.0.1, for all *-linux triples, .init_array/.finit_array
are used by default.
There is a toggle -fno-use-init-array (not in GCC) to switch back to
.ctors/.dtors
Modern GCC also uses .init_array. The minimum requirement is now GCC
4.9 and thus I wonder whether the .ctors configuration is still
supported.
If it is (maybe because glibc version which is not specified on
https://www.kernel.org/doc/html/latest/process/changes.html ), we
should use
some #if to highlight that.
> > ~GCC 4.7 switched to default to .init_array/.fini_array if libc
> > supports it. I have some refactoring in this area of Clang as well
> > (e.g.
https://reviews.llvm.org/D71393)
> >
> > And I am not sure SORT(.init_array.*) or SORT(.ctors.*) will work. The
> > correct construct is SORT_BY_INIT_PRIORITY(.init_array.*)
>
> The kernel doesn't seem to use the init_priority attribute at all. Are
> you saying the cause of the .ctors.* names are a result of some internal
> use of init_priority by the compiler here?
>
If no priority is intended, consider deleting SORT to avoid confusion?