This patchset is a PoC showing, it is possible and advantageous to integrate platform setup code in the kernel tree instead of maintaining it in a separate bootloader project. Bringing up a new ARM platform today requires developing the following pieces code in both bootloader and kernel: + platform setup (DRAM, minimal set of clocks and PMICs etc) - minimal setup in bootloader - full setup in kernel + device drivers (storage, network interface, display) - in both bootloader and kernel We've noticed that most code required in bootloader can be ported from Linux. This isn't, however, effortless. We also consider further maintenance of two copies of code an unnecessary burden. Making platform setup code a part of kernel source tree makes it possible to reuse existing Linux drivers in bootloading environment as well as to avoid creating and maintainig two different drivers for new devices. The following patches enables building Linux image that is loadable directly by Odroid XU4's firmware (bl2). The goal for such arrangement is to use Linux as a boot loader that later runs a full OS using kexec. Hardkernel, the vendor of Odroid XU4, provides signed, and thus, cumbersome to replace, platform setup code (bl1 and bl2). We decided not to replace them, but rather make the kernel loadable by the bl2 code by adding only a tiny amount of code to set up the consol. The kernel needs, however, to be small enough to be loaded succesfully (1 MiB). The patchset also provides hsinit (in tools/hsinit) userland program, which is a tiny init program that extracts designated archive to initramfs and executes /init. At the moment any initramfs image can be used at this stage. Although hsinit can be linked against glibc it makes little sense because together with the kernel it wont fit in 1 MiB. Instead it is recommended to link hsinit against musl libc. Install musl from your OS vendor or follow the upstream instructions. With musl available enter tools/hsinit and run the following commands. --8<---------------cut here---------------start------------->8--- wget -P vendor/ https://libarchive.org/downloads/libarchive-3.3.2.tar.gz wget -P vendor/ http://prdownloads.sourceforge.net/libpng/zlib-1.2.11.tar.gz ./bootstrap MUSL_DIR=/usr/lib/arm-linux-musleabi/ \ GCC_CROSS_DIR=/usr/lib/gcc-cross/arm-linux-gnueabi/8/ \ CPPFLAGS='-nostdinc -isystem /usr/include/arm-linux-musleabi/' \ CFLAGS='-mthumb -Os -ffunction-sections -fdata-sections' \ LIBARCHIVE_CPP_FLAGS=-I/usr/include/arm-linux-musleabi/ \ LIBARCHIVE_C_FLAGS=$CFLAGS \ ZLIB_C_FLAGS=$CFLAGS \ LDFLAGS="-nostdlib -L${MUSL_DIR}/ -L${GCC_CROSS_DIR}/ ${MUSL_DIR}/crt1.o ${MUSL_DIR}/crti.o ${GCC_CROSS_DIR}/crtbegin.o -Wl,--gc-sections -Wl,--start-group ${GCC_CROSS_DIR}/libgcc.a ${GCC_CROSS_DIR}/libgcc_eh.a -Wl,--end-group ${GCC_CROSS_DIR}/crtend.o ${MUSL_DIR}/crtn.o -s" \ LIBS="-lc -lgcc" \ ./configure --enable-local-libraries --host=arm-linux-gnueabi --enable-static make --8<---------------cut here---------------end--------------->8--- To build bootImage file that is loadable by Odroid XU4's bl2 the following commands need to be issued (CROSS_COMPILE and ARCH ommited) --8<---------------cut here---------------start------------->8--- make odroidxu4_bootloader_defconfig make dtbs make bootImage --8<---------------cut here---------------end--------------->8--- The resulting arch/arm/boot/bootImage should be renamed to u-boot-mmc.bin and flashed onto an SD or eMMC card with sd_fusing scritp. Łukasz Stelmach (4): scripts/dtc: update fdtget.c to upstream version v1.4.7-57-gf267e674d145 scripts: add get_console_base.pl Add tools/hsinit boot/loader: Enable building bootloader replacement for Odroid XU4 arch/arm/Kconfig | 8 + arch/arm/Makefile | 8 +- arch/arm/boot/Makefile | 17 + arch/arm/boot/loader/Kconfig | 23 ++ arch/arm/boot/loader/Makefile | 42 +++ arch/arm/boot/loader/odroid-console.c | 136 ++++++++ arch/arm/boot/loader/odroid-crt0.S | 40 +++ arch/arm/boot/loader/piggy.S | 14 + arch/arm/boot/loader/vectors.S | 112 +++++++ arch/arm/boot/loader/vmlinux.lds | 17 + .../configs/odroidxu4_bootloader_defconfig | 127 ++++++++ scripts/dtc/.gitignore | 4 + scripts/dtc/Makefile | 5 + scripts/dtc/fdtget.c | 125 ++++---- scripts/dtc/update-dtc-source.sh | 4 +- scripts/get_console_base.pl | 26 ++ tools/hsinit/Makefile.am | 29 ++ tools/hsinit/README.org | 56 ++++ tools/hsinit/bootstrap | 7 + tools/hsinit/configure.ac | 128 ++++++++ tools/hsinit/hsinit.c | 299 ++++++++++++++++++ tools/hsinit/vendor/.gitignore | 5 + tools/hsinit/vendor/SHA256SUMS | 2 + 23 files changed, 1177 insertions(+), 57 deletions(-) create mode 100644 arch/arm/boot/loader/Kconfig create mode 100644 arch/arm/boot/loader/Makefile create mode 100644 arch/arm/boot/loader/odroid-console.c create mode 100644 arch/arm/boot/loader/odroid-crt0.S create mode 100644 arch/arm/boot/loader/piggy.S create mode 100644 arch/arm/boot/loader/vectors.S create mode 100644 arch/arm/boot/loader/vmlinux.lds create mode 100644 arch/arm/configs/odroidxu4_bootloader_defconfig create mode 100755 scripts/get_console_base.pl create mode 100644 tools/hsinit/Makefile.am create mode 100644 tools/hsinit/README.org create mode 100755 tools/hsinit/bootstrap create mode 100644 tools/hsinit/configure.ac create mode 100644 tools/hsinit/hsinit.c create mode 100644 tools/hsinit/vendor/.gitignore create mode 100644 tools/hsinit/vendor/SHA256SUMS -- 2.20.1
