How to fail an ARMv5T u-boot build when libgcc is ARMv7T2?

[Richard Earnshaw]

On 10/11/11 10:04, Loïc Minier wrote:
>         Hey
>
>  When building u-boot for an ARMv5T platform (versatileqemu_config), the
>  Ubuntu-packaged Linaro cross-toolchain isn't suitable because it
>  only offers an ARMv7T2 libgcc.  But I'd like the build to fail when
>  that happens rather than silently generating an u-boot.bin which will
>  trigger a SIGILL when it hits the first non-ARMv5T instruction.
>
>  I heard that gcc/ld are supposed to check this, but I'm not sure how
>  it's supposed to work; perhaps the way u-boot does its final link
>  prevents this from working properly?
>
>  I tried building u-boot as follows:
>     make O=obj-broken \
>         CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm \
>         OPTFLAGS="-marm -march=armv5te" \
>         versatileqemu_config
>
>     make O=obj-broken \
>         CROSS_COMPILE=arm-linux-gnueabi- ARCH=arm \
>         OPTFLAGS="-marm -march=armv5te" \
>         -j2
>
>  The final link looks like this:
> UNDEF_SYM=`arm-linux-gnueabi-objdump -x /home/lool/git/denx/u-boot/obj-v-broken/board/armltd/versatile/libversatile.o /home/lool/git/denx/u-boot/obj-v-broken/api/libapi.o /home/lool/git/denx/u-boot/obj-v-broken/arch/arm/cpu/arm926ejs/libarm926ejs.o /home/lool/git/denx/u-boot/obj-v-broken/arch/arm/cpu/arm926ejs/versatile/libversatile.o /home/lool/git/denx/u-boot/obj-v-broken/arch/arm/lib/libarm.o /home/lool/git/denx/u-boot/obj-v-broken/common/libcommon.o /home/lool/git/denx/u-boot/obj-v-broken/disk/libdisk.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/bios_emulator/libatibiosemu.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/block/libblock.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/dma/libdma.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/fpga/libfpga.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/gpio/libgpio.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/hwmon/libhwmon.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/i2c/libi2c.o /home/lool/git/denx
/u-boot/obj-v-broken/drivers/input/libinput.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/misc/libmisc.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/mmc/libmmc.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/mtd/libmtd.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/mtd/nand/libnand.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/mtd/onenand/libonenand.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/mtd/spi/libspi_flash.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/mtd/ubi/libubi.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/net/libnet.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/net/phy/libphy.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/pci/libpci.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/pcmcia/libpcmcia.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/power/libpower.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/rtc/librtc.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/serial/libserial.o /home/lool/git/denx/u-boot/obj-v-bro
ken/drivers/spi/libspi.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/twserial/libtws.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/usb/eth/libusb_eth.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/usb/gadget/libusb_gadget.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/usb/host/libusb_host.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/usb/musb/libusb_musb.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/usb/phy/libusb_phy.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/video/libvideo.o /home/lool/git/denx/u-boot/obj-v-broken/drivers/watchdog/libwatchdog.o /home/lool/git/denx/u-boot/obj-v-broken/fs/cramfs/libcramfs.o /home/lool/git/denx/u-boot/obj-v-broken/fs/ext2/libext2fs.o /home/lool/git/denx/u-boot/obj-v-broken/fs/fat/libfat.o /home/lool/git/denx/u-boot/obj-v-broken/fs/fdos/libfdos.o /home/lool/git/denx/u-boot/obj-v-broken/fs/jffs2/libjffs2.o /home/lool/git/denx/u-boot/obj-v-broken/fs/reiserfs/libreiserfs.o /home/lool/git/denx/u-boot/obj-v-broken/fs/ubi
fs/libubifs.o /home/lool/git/denx/u-boot/obj-v-broken/fs/yaffs2/libyaffs2.o /home/lool/git/denx/u-boot/obj-v-broken/lib/libfdt/libfdt.o /home/lool/git/denx/u-boot/obj-v-broken/lib/libgeneric.o /home/lool/git/denx/u-boot/obj-v-broken/lib/lzma/liblzma.o /home/lool/git/denx/u-boot/obj-v-broken/lib/lzo/liblzo.o /home/lool/git/denx/u-boot/obj-v-broken/lib/zlib/libz.o /home/lool/git/denx/u-boot/obj-v-broken/net/libnet.o /home/lool/git/denx/u-boot/obj-v-broken/post/libpost.o | sed  -n -e 's/.*\(__u_boot_cmd_.*\)/-u\1/p'|sort|uniq`; cd /home/lool/git/denx/u-boot/obj-v-broken && arm-linux-gnueabi-ld  -pie -T /home/lool/git/denx/u-boot/obj-v-broken/u-boot.lds -Bstatic -Ttext 0x10000 $UNDEF_SYM arch/arm/cpu/arm926ejs/start.o --start-group api/libapi.o arch/arm/cpu/arm926ejs/libarm926ejs.o arch/arm/cpu/arm926ejs/versatile/libversatile.o arch/arm/lib/libarm.o common/libcommon.o disk/libdisk.o drivers/bios_emulator/libatibiosemu.o drivers/block/libblock.o drivers/dma/libdma.o drivers/fpga/
libfpga.o drivers/gpio/libgpio.o drivers/hwmon/libhwmon.o drivers/i2c/libi2c.o drivers/input/libinput.o drivers/misc/libmisc.o drivers/mmc/libmmc.o drivers/mtd/libmtd.o drivers/mtd/nand/libnand.o drivers/mtd/onenand/libonenand.o drivers/mtd/spi/libspi_flash.o drivers/mtd/ubi/libubi.o drivers/net/libnet.o drivers/net/phy/libphy.o drivers/pci/libpci.o drivers/pcmcia/libpcmcia.o drivers/power/libpower.o drivers/rtc/librtc.o drivers/serial/libserial.o drivers/spi/libspi.o drivers/twserial/libtws.o drivers/usb/eth/libusb_eth.o drivers/usb/gadget/libusb_gadget.o drivers/usb/host/libusb_host.o drivers/usb/musb/libusb_musb.o drivers/usb/phy/libusb_phy.o drivers/video/libvideo.o drivers/watchdog/libwatchdog.o fs/cramfs/libcramfs.o fs/ext2/libext2fs.o fs/fat/libfat.o fs/fdos/libfdos.o fs/jffs2/libjffs2.o fs/reiserfs/libreiserfs.o fs/ubifs/libubifs.o fs/yaffs2/libyaffs2.o lib/libfdt/libfdt.o lib/libgeneric.o lib/lzma/liblzma.o lib/lzo/liblzo.o lib/zlib/libz.o net/libnet.o post/libpost.o
 board/armltd/versatile/libversatile.o --end-group /home/lool/git/denx/u-boot/obj-v-broken/arch/arm/lib/eabi_compat.o  -L /usr/lib/gcc/arm-linux-gnueabi/4.6.1 -lgcc -Map u-boot.map -o u-boot
>
>  I verified that all the .o files passed above have Tag_CPU_name:
>  "5TE" in their arm-linux-gnueabi-readelf -A output; the only
>  problematic file is -lgcc.
>
>  Note that the final link is done with arm-linux-gnueabi-ld and doesn't
>  set any architecture; I changed it manually to use gcc and pass the
>  -marm -march=armv5te, and had to set -nostdlib too when using gcc:
> arm-linux-gnueabi-gcc -marm -march=armv5te -nostdlib -pie -T /home/lool/git/denx/u-boot/obj-v-broken/u-boot.lds -Bstatic -Ttext 0x10000 $UNDEF_SYM arch/arm/cpu/arm926ejs/start.o -Wl,--start-group api/libapi.o arch/arm/cpu/arm926ejs/libarm926ejs.o arch/arm/cpu/arm926ejs/versatile/libversatile.o arch/arm/lib/libarm.o common/libcommon.o disk/libdisk.o drivers/bios_emulator/libatibiosemu.o drivers/block/libblock.o drivers/dma/libdma.o drivers/fpga/libfpga.o drivers/gpio/libgpio.o drivers/hwmon/libhwmon.o drivers/i2c/libi2c.o drivers/input/libinput.o drivers/misc/libmisc.o drivers/mmc/libmmc.o drivers/mtd/libmtd.o drivers/mtd/nand/libnand.o drivers/mtd/onenand/libonenand.o drivers/mtd/spi/libspi_flash.o drivers/mtd/ubi/libubi.o drivers/net/libnet.o drivers/net/phy/libphy.o drivers/pci/libpci.o drivers/pcmcia/libpcmcia.o drivers/power/libpower.o drivers/rtc/librtc.o drivers/serial/libserial.o drivers/spi/libspi.o drivers/twserial/libtws.o drivers/usb/eth/libusb_eth.o drivers/usb/
gadget/libusb_gadget.o drivers/usb/host/libusb_host.o drivers/usb/musb/libusb_musb.o drivers/usb/phy/libusb_phy.o drivers/video/libvideo.o drivers/watchdog/libwatchdog.o fs/cramfs/libcramfs.o fs/ext2/libext2fs.o fs/fat/libfat.o fs/fdos/libfdos.o fs/jffs2/libjffs2.o fs/reiserfs/libreiserfs.o fs/ubifs/libubifs.o fs/yaffs2/libyaffs2.o lib/libfdt/libfdt.o lib/libgeneric.o lib/lzma/liblzma.o lib/lzo/liblzo.o lib/zlib/libz.o net/libnet.o post/libpost.o board/armltd/versatile/libversatile.o -Wl,--end-group /home/lool/git/denx/u-boot/obj-v-broken/arch/arm/lib/eabi_compat.o  -L /usr/lib/gcc/arm-linux-gnueabi/4.6.1 -lgcc -Wl,-Map u-boot.map -o u-boot
>
>  But this command works and produces an u-boot ELF which has
>  Tag_CPU_name: "7-A".
>

The build attributes were never intended to be used in executables; the
format is too expensive to decode in most situations.  Instead the ABI
specification included an optional PHEADER that had a highly simplified
indication of the executable compatibility of an image (essentially the
architecture).  Unfortunately this has never been added to GNU Binutils.

See PT_ARM_ARCHEXT in the ARM ELF specification (available from infocenter).

R.

>  How would I break the build when libgcc isn't ARMv5T?
>
>    Thanks,


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Richard Earnshaw             Email: Richard.Earnshaw at arm.com
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