On Tue, Sep 15, 2020 at 10:55 PM Ard Biesheuvel [off-list ref] wrote:

On Wed, 16 Sep 2020 at 02:31, Nick Desaulniers [off-list ref] wrote:

quoted

On Tue, Sep 15, 2020 at 2:30 PM Ard Biesheuvel [off-list ref] wrote:

quoted

Excellent, thanks for testing. Do you have any coverage for Thumb2
builds as well? (CONFIG_THUMB2_KERNEL=y)

Ah, right, manually testing ARCH=arm defconfig with
CONFIG_THUMB2_KERNEL enabled via menuconfig:

Builds and boots for clang.

(Also needed https://lore.kernel.org/lkml/20200915225751.274531-1-ndesaulniers@google.com/T/#u (local)
for an unrelated issue).

For GCC, I observe:

arch/arm/vfp/vfphw.o: in function `vfp_support_entry':
(.text+0xa): relocation truncated to fit: R_ARM_THM_JUMP19 against
symbol `vfp_kmode_exception' defined in .text.unlikely section in
arch/arm/vfp/vfpmodule.o

Interesting. And this is using ld.bfd ?

$ arm-linux-gnueabihf-ld --version
GNU ld (GNU Binutils for Debian) 2.34

.text.unlikely reminds me of the sections created when profiling data
is present.  That's obviously not the case here, so maybe there's
other ways this section can be created by GCC?  I may have added a
patch recently for placing this section explicitly, which was a
prerequisite for Kees' series explicitly placing all sections.
https://lore.kernel.org/lkml/159896087937.20229.4955362311782724603.tip-bot2@tip-bot2/ (local)
Maybe that can be improved?

IIRC, LLD is able to emit range extension thunks for these cases, but
BFD does not.
-- 
Thanks,
~Nick Desaulniers

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