grub: support build on x86-64, and misc other improvements

This commit brings a number of improvements to the grub packaging:

 * It builds grub with the host compiler, which is needed so that we
   can build a 32 bits grub even if the target architecture is
   x86-64. To make sure we have a host compiler capable of generating
   32 bits code, grub now selects the BR2_HOSTARCH_NEEDS_IA32_COMPILER
   option. Building with the host compiler is done by cheating and
   passing $(HOST_CONFIGURE_OPTS) in GRUB_CONF_ENV.

 * Some additional CFLAGS are added to make sure grub builds properly
   with modern compilers (-O0, --build-id=none, -fno-stack-protector).

 * Removal of the GRUB_INSTALL_STAGING_CMDS which were not used, since
   GRUB_INSTALL_STAGING was not set to YES.

 * Installation of the "grub" binary in $(HOST_DIR) instead of
   $(TARGET_DIR) since it's actually used only on the host to install
   grub into an image or device.

 * Removal of the grub uninstall commands, since they are generally
   considered useless.

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

boot/grub/Config.in

@@ -1,6 +1,7 @@
 config BR2_TARGET_GRUB
 	bool "grub"
 	depends on BR2_i386 || BR2_x86_64
+	select BR2_HOSTARCH_NEEDS_IA32_COMPILER
 	help
 	  The GRand Unified Bootloader for x86 systems.
 

boot/grub/grub.mk

@@ -12,10 +12,15 @@ GRUB_SITE   = http://snapshot.debian.org/archive/debian/20080329T000000Z/pool/ma
 GRUB_LICENSE = GPLv2+
 GRUB_LICENSE_FILES = COPYING
 
-GRUB_CFLAGS=-DSUPPORT_LOOPDEV
-ifeq ($(BR2_LARGEFILE),)
-GRUB_CFLAGS+=-U_FILE_OFFSET_BITS
-endif
+# Passing -O0 since the default -O2 passed by Buildroot generates
+# non-working stage2.  Passing --build-id=none to the linker, because
+# the ".note.gnu.build-id" ELF sections generated by default confuse
+# objcopy when generating raw binaries. Passing -fno-stack-protector
+# to avoid undefined references to __stack_chk_fail.
+GRUB_CFLAGS = \
+	-DSUPPORT_LOOPDEV \
+	-O0 -Wl,--build-id=none \
+	-fno-stack-protector
 
 GRUB_CONFIG-$(BR2_TARGET_GRUB_SPLASH) += --enable-graphics
 GRUB_CONFIG-$(BR2_TARGET_GRUB_DISKLESS) += --enable-diskless
@@ -51,24 +56,26 @@ endef
 GRUB_POST_PATCH_HOOKS += GRUB_DEBIAN_PATCHES
 
 GRUB_CONF_ENV = \
-	CFLAGS="$(TARGET_CFLAGS) $(GRUB_CFLAGS)"
+	$(HOST_CONFIGURE_OPTS) \
+	CFLAGS="$(HOST_CFLAGS) $(GRUB_CFLAGS)"
 
 GRUB_CONF_OPT = \
 	--disable-auto-linux-mem-opt \
 	$(GRUB_CONFIG-y)
 
-define GRUB_INSTALL_STAGING_CMDS
-	install -m 0755 -D $(@D)/grub/grub $(STAGING_DIR)/sbin/grub
-endef
-
 ifeq ($(BR2_TARGET_GRUB_SPLASH),y)
 define GRUB_INSTALL_SPLASH
 	cp boot/grub/splash.xpm.gz $(TARGET_DIR)/boot/grub/
 endef
 endif
 
+# We're cheating here as we're installing the grub binary not in the
+# target directory (where it is useless), but in the host
+# directory. This grub binary can be used to install grub into the MBR
+# of a disk or disk image.
+
 define GRUB_INSTALL_TARGET_CMDS
-	install -m 0755 -D $(@D)/grub/grub $(TARGET_DIR)/sbin/grub
+	install -m 0755 -D $(@D)/grub/grub $(HOST_DIR)/sbin/grub
 	mkdir -p $(TARGET_DIR)/boot/grub
 	cp $(@D)/stage1/stage1 $(TARGET_DIR)/boot/grub
 	cp $(@D)/stage2/*1_5   $(TARGET_DIR)/boot/grub
@@ -76,13 +83,4 @@ define GRUB_INSTALL_TARGET_CMDS
 	$(GRUB_INSTALL_SPLASH)
 endef
 
-define GRUB_UNINSTALL_STAGING_CMDS
-	rm -f $(STAGING_DIR)/sbin/grub
-endef
-
-define GRUB_UNINSTALL_TARGET_CMDS
-	rm -f $(TARGET_DIR)/sbin/grub
-	rm -rf $(TARGET_DIR)/boot/grub
-endef
-
 $(eval $(autotools-package))