[Buildroot] [PATCH] package/libnss: fix build failure on arm32 arch not armv7

[Giulio Benetti]

Hi Thomas,

just sent a v2 for this with upstreamed patch:
https://patchwork.ozlabs.org/patch/1266204/

Best regards
-- 
Giulio Benetti
Benetti Engineering sas

On 3/25/20 4:13 PM, Giulio Benetti wrote:
> Hi Thomas,
> 
> On 3/25/20 3:45 PM, Thomas Petazzoni wrote:
>> On Wed, 25 Mar 2020 15:31:08 +0100
>> Giulio Benetti <giulio.benetti at benettiengineering.com> wrote:
>>
>>> +diff --git a/nss/lib/freebl/Makefile b/nss/lib/freebl/Makefile
>>> +index dc502f309..c7eb9c205 100644
>>> +--- a/nss/lib/freebl/Makefile
>>> ++++ b/nss/lib/freebl/Makefile
>>> +@@ -781,7 +781,7 @@ ifeq ($(CPU_ARCH),arm)
>>> + USES_SOFTFLOAT_ABI := $(shell $(CC) -o - -E -dM - $(CFLAGS) < /dev/null | grep __SOFTFP__ > /dev/null && echo 1)
>>> + $(OBJDIR)/$(PROG_PREFIX)aes-armv8$(OBJ_SUFFIX): CFLAGS += -march=armv8-a -mfpu=crypto-neon-fp-armv8$(if $(USES_SOFTFLOAT_ABI), -mfloat-abi=softfp)
>>> + ifndef NSS_DISABLE_GCM_ARM32_NEON
>>> +-$(OBJDIR)/$(PROG_PREFIX)gcm-arm32-neon$(OBJ_SUFFIX): CFLAGS += -march=armv7 -mfpu=neon$(if $(USES_SOFTFLOAT_ABI), -mfloat-abi=softfp)
>>> ++$(OBJDIR)/$(PROG_PREFIX)gcm-arm32-neon$(OBJ_SUFFIX): CFLAGS += -mfpu=neon$(if $(USES_SOFTFLOAT_ABI), -mfloat-abi=softfp)
>>
>> But only ARMv7 can have NEON support support. So removing just
>> -march=armv7 doesn't make sense. Actually, the issue is probably that
>> they should be using -march=armv7-a, because -march=armv7 is the common
>> subset of ARMv7-A, ARMv7-M and ARMv7-R, which I suppose doesn't include
>> NEON.
>>
>> So while the patch work, its description is misleading at best,
> 
> yes, sorry
> 
>> and
>> having -march=armv7-a here is probably the right fix.
> 
> But build failure we have here:
> https://gitlab.com/buildroot.org/buildroot/-/jobs/483712746
> is on cortex-A53 in 32-bit mode, so NEON is present and we are on arm,
> but it is an armv8, not armv7, so we can't pass -march=armv7 to gcc.
> 
> Also they have added -march=armv7 to fix an armv6 build failure:
> https://bugzilla.mozilla.org/show_bug.cgi?id=1612177
> but how can that work on armv6? Probably it builds because -march=armv7
> emits NEON macro in some way, but it shouldn't run correctly.
> 
> So basically with a better description I think my patch is correct.
> The problem here is the case on armv8(32-bits mode) with -march=armv7
> 
> Another way is to avoid building gcm-arm32-neon.c on armv8 in 32 bits mode.
> 
> What do you think?
> 
> Kind regards
>