external-toolchain: Support for multilib toolchains

Multilib toolchains provide different versions of the base libraries
for different architecture variants. For example, the ARM Codesourcery
toolchain provides base libraries for ARMv5 (default), ARMv4t and
Thumb2.

Depending on the -march= argument passed to gcc, the sysroot used by
the compiler is therefore different. This means that the sysroot
location in CROSS-gcc -v cannot be used. Instead, we must use
CROSS-gcc -print-sysroot when available and fall back to the old way
if unavailable.

Moreover, we cannot simply copy the full sysroot as we used to do,
because the sysroot organization of multilib toolchain is more
complicated. In Codesourcery toolchains, we have :

 /
   etc      -- for ARMv5
   lib      -- for ARMv5
   sbin     -- for ARMv5
   usr      -- for ARMv5 (includes headers)
   armv4t
     etc    -- for ARMv4t
     lib    -- for ARMv4t
     sbin   -- for ARMv4t
     usr    -- for ARMv4t (no headers!)
   thumb2
     etc    -- for Thumb2
     lib    -- for Thumb2
     sbin   -- for Thumb2
     usr    -- for Thumb2 (no headers!)

So we have the default ARMv5 architecture variant that is installed in
the main directory, and we have subdirectories for the ARMv4t and
Thumb2 architecture variants.

Copying the full sysroot to the staging directory doesn't work. All
our packages are based on the fact that they should install libraries
in staging/usr/lib. But if ARMv4t is used, the compiler would only
look in staging/armv4t/usr/lib for libraries (even when overriding the
sysroot with the --sysroot option, the multilib compiler suffixes the
sysroot directory with the architecture variant if it matches a
recognized one).

Therefore, we have to copy only the sysroot that we are interested
in. This is rendered a little bit complicated by the fact that the
armv4t and thumb2 sysroot do not contain the headers since they are
shared with the armv5 sysroot.

So, this patch :

 * Modifies how we compute SYSROOT_DIR in order to use -print-sysroot
   if it exists. SYSROOT_DIR contains the location of the main sysroot
   directory, i.e the sysroot for the default architecture variant.

 * Defines ARCH_SUBDIR as the subdirectory in the main sysroot for the
   currently selected architecture variant (in our case, it can be
   ".", "armv4t" or "thumb2"). ARCH_SYSROOT_DIR is defined as the full
   path to the sysroot of the currently selected architecture variant.

 * Modifies copy_toolchain_lib_root (which copies a library to the
   target/ directory) so that libraries are taken from
   ARCH_SYSROOT_DIR instead of SYSROOT_DIR. This ensures that
   libraries for the correct architecture variant are properly copied
   to the target.

 * Modifies copy_toolchain_sysroot (which copies the sysroot to the
   staging/ directory), so that it copies the contents of
   ARCH_SYSROOT_DIR, and if needed, adds the headers from the main
   sysroot directory and a symbolic link (armv4t -> . or thumb2 -> .)
   to make the compiler believe that its sysroot is really in armv4t/
   or thumb2/.

Tested with Codesourcery 2009q1 ARM toolchain, Crosstool-NG ARM glibc
and ARM uClibc toolchains.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

1 files changed, 79 insertions, 11 deletions

diff --git a/toolchain/external-toolchain/ext-tool.mk b/toolchain/external-toolchain/ext-tool.mk
index 29a5ccab9..2c2562cde 100644
--- a/toolchain/external-toolchain/ext-tool.mk
+++ b/toolchain/external-toolchain/ext-tool.mk
@@ -2,7 +2,12 @@
 #
 # This file implements the support for external toolchains, i.e
 # toolchains that have not been produced by Buildroot itself and that
-# are already available on the system on which Buildroot runs.
+# are already available on the system on which Buildroot runs. So far,
+# we have tested this with:
+#
+#  * Toolchains generated by Crosstool-NG
+#  * Toolchains generated by Buildroot
+#  * ARM toolchains made available by Codesourcery
 #
 # The basic principle is the following
 #
@@ -35,23 +40,22 @@
 # directory to the target directory. Also optionaly strips the
 # library.
 #
-# $1: sysroot directory
+# $1: arch specific sysroot directory
 # $2: library name
 # $3: destination directory
 # $4: strip (y|n), default is to strip
 #
 copy_toolchain_lib_root = \
-	SYSROOT_DIR="$(strip $1)"; \
+	ARCH_SYSROOT_DIR="$(strip $1)"; \
 	LIB="$(strip $2)"; \
-	DST="$(strip $3)"; \
 	STRIP="$(strip $4)"; \
  \
-	LIBS=`(cd $${SYSROOT_DIR}; find . -path "./lib/$${LIB}.*" -o -path "./usr/lib/$${LIB}.*")` ; \
+	LIBS=`(cd $${ARCH_SYSROOT_DIR}; find . -path "./lib/$${LIB}.*" -o -path "./usr/lib/$${LIB}.*")` ; \
 	for FILE in $${LIBS} ; do \
 		LIB=`basename $${FILE}`; \
 		LIBDIR=`dirname $${FILE}` ; \
 		while test \! -z "$${LIB}"; do \
-			FULLPATH="$${SYSROOT_DIR}/$${LIBDIR}/$${LIB}" ; \
+			FULLPATH="$${ARCH_SYSROOT_DIR}/$${LIBDIR}/$${LIB}" ; \
 			rm -fr $(TARGET_DIR)/$${LIBDIR}/$${LIB}; \
 			mkdir -p $(TARGET_DIR)/$${LIBDIR}; \
 			if test -h $${FULLPATH} ; then \
@@ -76,13 +80,54 @@ copy_toolchain_lib_root = \
 
 #
 # Copy the full external toolchain sysroot directory to the staging
-# dir
+# dir. The operation of this function is rendered a little bit
+# complicated by the support for multilib toolchains.
 #
-# $1: sysroot directory
+# We start by copying etc, lib, sbin and usr from the sysroot of the
+# selected architecture variant (as pointed by ARCH_SYSROOT_DIR). This
+# allows to import into the staging directory the C library and
+# companion libraries for the correct architecture variant. We
+# explictly only copy etc, lib, sbin and usr since other directories
+# might exist for other architecture variants (on Codesourcery
+# toolchain, the sysroot for the default architecture variant contains
+# the armv4t and thumb2 subdirectories, which are the sysroot for the
+# corresponding architecture variants), and we don't want to import
+# them.
+#
+# Then, if the selected architecture variant is not the default one
+# (i.e, if SYSROOT_DIR != ARCH_SYSROOT_DIR), then we :
+#
+#  * Import the header files from the default architecture
+#    variant. Header files are typically shared between the sysroots
+#    for the different architecture variants. If we use the
+#    non-default one, header files were not copied by the previous
+#    step, so we copy them here from the sysroot of the default
+#    architecture variant.
+#
+#  * Create a symbolic link that matches the name of the subdirectory
+#    for the architecture variant in the original sysroot. This is
+#    required as the compiler will by default look in
+#    sysroot_dir/arch_variant/ for libraries and headers, when the
+#    non-default architecture variant is used. Without this, the
+#    compiler fails to find libraries and headers.
+#
+# $1: main sysroot directory of the toolchain
+# $2: arch specific sysroot directory of the toolchain
+# $3: arch specific subdirectory in the sysroot
 #
 copy_toolchain_sysroot = \
 	SYSROOT_DIR="$(strip $1)"; \
-	cp -a $${SYSROOT_DIR}/* $(STAGING_DIR)/ ; \
+	ARCH_SYSROOT_DIR="$(strip $2)"; \
+	ARCH_SUBDIR="$(strip $3)"; \
+	for i in etc lib sbin usr ; do \
+		cp -a $${ARCH_SYSROOT_DIR}/$$i $(STAGING_DIR)/ ; \
+	done ; \
+	if [ `readlink -f $${SYSROOT_DIR}` != `readlink -f $${ARCH_SYSROOT_DIR}` ] ; then \
+		if [ ! -d $${ARCH_SYSROOT_DIR}/usr/include ] ; then \
+			cp -a $${SYSROOT_DIR}/usr/include $(STAGING_DIR)/usr ; \
+		fi ; \
+		ln -s . $(STAGING_DIR)/$(ARCH_SUBDIR) ; \
+	fi ; \
 	find $(STAGING_DIR) -type d | xargs chmod 755
 
 #
@@ -208,7 +253,30 @@ ifeq ($(BR2_INSTALL_LIBSTDCPP),y)
 EXTERNAL_LIBS+=libstdc++.so
 endif
 
+# SYSROOT_DIR selection. We first try the -print-sysroot option,
+# available in gcc 4.4.x and in some Codesourcery toolchains. If this
+# option is not available, we fallback to the value of --with-sysroot
+# as visible in CROSS-gcc -v. We don't pass the -march= option to gcc
+# as we want the "main" sysroot, which contains all variants of the C
+# library in the case of multilib toolchains.
+SYSROOT_DIR=$(shell $(TARGET_CC) -print-sysroot 2>/dev/null)
+ifeq ($(SYSROOT_DIR),)
 SYSROOT_DIR=$(shell readlink -f $$(LANG=C $(TARGET_CC) -print-file-name=libc.a |sed -r -e 's:usr/lib/libc\.a::;'))
+endif
+
+# Now, find if the toolchain specifies a sub-directory for the
+# specific architecture variant we're interested in. This is the case
+# with multilib toolchain, when the selected architecture variant is
+# not the default one. To do so, we ask the compiler by passing the
+# appropriate -march= flags. ARCH_SUBDIR will contain the
+# subdirectory, in the main SYSROOT_DIR, that corresponds to the
+# selected architecture variant. ARCH_SYSROOT_DIR will contain the
+# full path to this location.
+ifneq ($(CC_TARGET_ARCH_),)
+TARGET_CC_ARCH_CFLAGS+=-march=$(CC_TARGET_ARCH_)
+endif
+ARCH_SUBDIR=$(shell $(TARGET_CC) $(TARGET_CC_ARCH_CFLAGS) -print-multi-directory)
+ARCH_SYSROOT_DIR=$(SYSROOT_DIR)/$(ARCH_SUBDIR)
 
 $(STAMP_DIR)/ext-toolchain-installed:
 	@echo "Checking external toolchain settings"
@@ -228,8 +296,8 @@ endif
 	mkdir -p $(TARGET_DIR)/lib
 	@echo "Copy external toolchain libraries to target..."
 	$(Q)for libs in $(EXTERNAL_LIBS); do \
-		$(call copy_toolchain_lib_root,$(SYSROOT_DIR),$$libs,/lib,$(BR2_TOOLCHAIN_EXTERNAL_STRIP)); \
+		$(call copy_toolchain_lib_root,$(ARCH_SYSROOT_DIR),$$libs,$(BR2_TOOLCHAIN_EXTERNAL_STRIP)); \
 	done
 	@echo "Copy external toolchain sysroot to staging..."
-	$(Q)$(call copy_toolchain_sysroot,$(SYSROOT_DIR))
+	$(Q)$(call copy_toolchain_sysroot,$(SYSROOT_DIR),$(ARCH_SYSROOT_DIR),$(ARCH_SUBDIR))
 	@touch $@