Re: [PATCH 1/3] ARM: use arch_extension directive instead of arch argument

[Arnd Bergmann]

On Sun, Mar 24, 2019 at 3:06 AM Arnd Bergmann <arnd@xxxxxxxx> wrote:
>
> On Sat, Mar 23, 2019 at 4:52 PM Stefan Agner <stefan@xxxxxxxx> wrote:
> >
> > The LLVM Target parser currently does not allow to specify the security
> > extension as part of -march (see also LLVM Bug 40186 [0]). When trying
> > to use Clang with LLVM's integrated assembler, this leads to a build
> > errors such as this:
> >   clang-8: error: the clang compiler does not support '-Wa,-march=armv7-a+sec'
> >
> > Use ".arch_extension sec" to enable the security extension in a more
> > portable fasion.
> >
> > Note that this is technically not exactly the same as the old code
> > checked for availabilty of the security extension by calling as-instr.
> > However, there are already other sites which use ".arch_extension sec"
> > unconditionally, hence de-facto we need an assembler capable of
> > ".arch_extension sec" already today (arch/arm/mm/proc-v7.S). The
> > arch extension "sec" is available since binutils 2.21 according to
> > its documentation [1].
> >
> > [0] https://bugs.llvm.org/show_bug.cgi?id=40186
> > [1] https://sourceware.org/binutils/docs-2.21/as/ARM-Options.html
> >
> > Signed-off-by: Stefan Agner <stefan@xxxxxxxx>
>
> This sounds like a good idea. I think we have platform specific
> minimum toolchain versions elsewhere, but I don't see a problem
> with raising the minimum version for all the armv7ve platforms.
>
> I've added this patch to my randconfig test queue, but please
> send it to arm@xxxxxxxxxx for inclusion when you have
> collected more Acks.
>
> Do you have a git tree with other patches required for the
> integrated assembler? I might try that out as well with
> my randconfig tree. At the moment I'm building with
> clang-8 and a small number of patches on top.
>
> Acked-by: Arnd Bergmann <arnd@xxxxxxxx>

I only now looked at the results and found a problem:
In a mixed v6/v7 configuration, the arch_extension flag
is not sufficient, and for armv6+sec, we get failures like

/git/arm-soc/arch/arm/mach-omap2/sleep44xx.S: Assembler messages:
/git/arm-soc/arch/arm/mach-omap2/sleep44xx.S:343: Error: selected
processor does not support `isb' in ARM mode
/git/arm-soc/arch/arm/mach-omap2/sleep44xx.S:350: Error: selected
processor does not support `dsb' in ARM mode
/git/arm-soc/arch/arm/mach-omap2/sleep44xx.S:351: Error: selected
processor does not support `dmb' in ARM mode
clang: error: assembler command failed with exit code 1 (use -v to see
invocation)
/git/arm-soc/scripts/Makefile.build:369: recipe for target
'arch/arm/mach-omap2/sleep44xx.o' failed
make[3]: *** [arch/arm/mach-omap2/sleep44xx.o] Error 1

==> build/arm/0x64728DCE_defconfig/log <==
/git/arm-soc/arch/arm/mach-omap2/omap-smc.S: Assembler messages:
/git/arm-soc/arch/arm/mach-omap2/omap-smc.S:31: Error: selected
processor does not support `dsb' in ARM mode
/git/arm-soc/arch/arm/mach-omap2/omap-smc.S:53: Error: selected
processor does not support `dsb' in ARM mode
/git/arm-soc/arch/arm/mach-omap2/omap-smc.S:54: Error: selected
processor does not support `dmb' in ARM mode

         Arnd