On Thu, Aug 5, 2021 at 11:27 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote: > > On Thu, Aug 5, 2021 at 6:58 AM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote: > > > > On Tue, Aug 3, 2021 at 3:39 AM 'Nick Desaulniers' via Clang Built > > Linux <clang-built-linux@xxxxxxxxxxxxxxxx> wrote: > > > diff --git a/Documentation/kbuild/llvm.rst b/Documentation/kbuild/llvm.rst > > > index b18401d2ba82..f8a360958f4c 100644 > > > --- a/Documentation/kbuild/llvm.rst > > > +++ b/Documentation/kbuild/llvm.rst > > > @@ -63,6 +63,23 @@ They can be enabled individually. The full list of the parameters: :: > > > Currently, the integrated assembler is disabled by default. You can pass > > > ``LLVM_IAS=1`` to enable it. > > > > > > +Omitting CROSS_COMPILE > > > +---------------------- > > > + > > > +As explained above, ``CROSS_COMPILE`` is used to set ``--target=<triple>``. > > > + > > > +Unless ``LLVM_IAS=1`` is specified, ``CROSS_COMPILE`` is also used to derive > > > +``--prefix=<path>`` to search for the GNU assembler and linker. > > > > > > Is there any place where we rely on --prefix > > to search for the linker? > > > > In general, the compiler stops after generating an object > > since it is passed with the -c option. > > The linking stage is separated. > > > > In the old days, VDSO was an exceptional case > > where $(CC) was used as the linker driver, but > > commit fe00e50b2db8c60e4ec90befad1f5bab8ca2c800 fixed it. > > See my previous reply to Fangrui. > https://lore.kernel.org/lkml/CAKwvOdnK=SUm1_--tcLRO3LVeXd_2Srfv2tsZCUW0uXXa1W_pg@xxxxxxxxxxxxxx/ > > To be more specific, I believe this is still a problem for ppc vdso. > https://github.com/ClangBuiltLinux/linux/issues/774 > > I had sent patches for that, but binutils 2.26 would crash (IIUC, > newer GNU binutils are ok). See this thread: > https://lore.kernel.org/lkml/b2066ccd-2b81-6032-08e3-41105b400f75@xxxxxxxxxx/ > > So "we'd prefer the linker was used as the driver, but there's at > least one place I know of in the tree where that's not currently the > case." Also, I think the CC_CAN_LINK functionality also fits the bill. https://github.com/ClangBuiltLinux/linux/issues/1290 -- Thanks, ~Nick Desaulniers
