toolchain: check ARM EABI vs. EABIhf for external toolchains

Following the introduction of the support of EABIhf as a second ARM ABI, it is important to check whether the external toolchain provided by the user actually uses the ABI that has been selected in the Buildroot configuration. This commit introduces such a check, using a similar solution to the one that was used to check OABI vs. EABI in the past.

Signed-off-by Thomas Petazzoni <[email protected]>

---
 toolchain/helpers.mk | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

toolchain/helpers.mk +0 -0

index 95217e7..dc21f8a 100644

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"Yann" == Yann E MORIN <[email protected]> writes:

toolchain/helpers.mk check_uclibc = \ · line 291

Quoted 5 lines

toolchain/helpers.mk +5 -0

+	else \
+		echo "Unsupported ABI of the external toolchain" ; \
+		exit 1 ; \
+	fi ; \
+	if [ x$(BR2_ARM_EABI) = x"y" -a $${EXT_TOOLCHAIN_ABI} = "eabihf" ] ; then \

toolchain/helpers.mk check_uclibc = \ · line 286

Quoted 7 lines

toolchain/helpers.mk +4 -2

 	EXT_TOOLCHAIN_TARGET=`LANG=C $${__CROSS_CC} -v 2>&1 | grep ^Target | cut -f2 -d ' '` ; \
-	if ! echo $${EXT_TOOLCHAIN_TARGET} | grep -qE 'eabi(hf)?$$' ; then \
-		echo "External toolchain uses the unsuported OABI" ; \
+	if echo $${EXT_TOOLCHAIN_TARGET} | grep -qE 'eabi$$' ; then \
+		EXT_TOOLCHAIN_ABI="eabi" ; \
+	elif echo $${EXT_TOOLCHAIN_TARGET} | grep -qE 'eabihf$$' ; then \
+		EXT_TOOLCHAIN_ABI="eabihf" ; \

That's not always the case. You can well have a toolchain which tuple ends in eabi, but the toolchain uses the hard-float ABI.

That's the case by default for crosstool-NG toolchains, for example. Since the *eabihf is recent, not all gcc or binutils versions recognise it, while they are absolutely capable of emitting EABI using the hard-float ABI. Hence, ct-ng allows adding the 'hf' suffix as an option. (see attachment for an example of 'gcc -v' dump).

Checking for EABI, it is better and more reliable to run the preprocessor, and check some defines are available or not (I always need a bit of googling to get this):

    ARM_TUPLE-gcc -E -dM -xc - </dev/null |grep __ARM_EABI__

However, I could not find a #define about the float ABI... :-(

toolchain/helpers.mk check_uclibc = \ · line 291

Quoted 5 lines

toolchain/helpers.mk +5 -0

+	else \
+		echo "Unsupported ABI of the external toolchain" ; \
+		exit 1 ; \
+	fi ; \
+	if [ x$(BR2_ARM_EABI) = x"y" -a $${EXT_TOOLCHAIN_ABI} = "eabihf" ] ; then \

Using this 'x$(VAR) = xy' construct is ugly. Just quote the variables, it is easier to read:

    if [ "$(BR2_ARM_EABI)" = "y" ... ]

The x$VAR construct was from a time when some shells where failing to test against an empty string. That time is long gone. Virtaully all shells can compare to empty strings, nowadays.

Quoted 17 lines · Yann E. MORIN

toolchain/helpers.mk check_uclibc = \ · line 286

Quoted 7 lines

toolchain/helpers.mk +4 -2

 	EXT_TOOLCHAIN_TARGET=`LANG=C $${__CROSS_CC} -v 2>&1 | grep ^Target | cut -f2 -d ' '` ; \
-	if ! echo $${EXT_TOOLCHAIN_TARGET} | grep -qE 'eabi(hf)?$$' ; then \
-		echo "External toolchain uses the unsuported OABI" ; \
+	if echo $${EXT_TOOLCHAIN_TARGET} | grep -qE 'eabi$$' ; then \
+		EXT_TOOLCHAIN_ABI="eabi" ; \
+	elif echo $${EXT_TOOLCHAIN_TARGET} | grep -qE 'eabihf$$' ; then \
+		EXT_TOOLCHAIN_ABI="eabihf" ; \

That's not always the case. You can well have a toolchain which tuple ends in eabi, but the toolchain uses the hard-float ABI.

That's the case by default for crosstool-NG toolchains, for example. Since the *eabihf is recent, not all gcc or binutils versions recognise it, while they are absolutely capable of emitting EABI using the hard-float ABI. Hence, ct-ng allows adding the 'hf' suffix as an option. (see attachment for an example of 'gcc -v' dump).

Quoted 6 lines

Checking for EABI, it is better and more reliable to run the preprocessor, and check some defines are available or not (I always need a bit of googling to get this):

    ARM_TUPLE-gcc -E -dM -xc - </dev/null |grep __ARM_EABI__

However, I could not find a #define about the float ABI... :-(

Ah, interesting. Originally, I wasn't planning on checking the tuple, and I was instead thinking of using a specific tag in the ELF headers.

A binary compiled with an EABIhf toolchain:

$ arm-linux-gnueabihf-readelf -A toto.o | grep Tag_ABI_VFP_args
  Tag_ABI_VFP_args: VFP registers

A binary compiled with an EABI toolchain:

$ arm-linux-gnueabihf-readelf -A toto.o | grep Tag_ABI_VFP_args
$

I would run this on the libc or ld.so provided with the toolchain.

What do you think?