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

[Arnd Bergmann]

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>