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Date:   Fri, 16 Nov 2018 13:13:52 -0800 (PST)
Subject:     Re: [PATCH] RISC-V: Build flat and compressed kernel images
In-Reply-To: <20181112055515.20341-1-anup@brainfault.org>
CC:     aou@eecs.berkeley.edu, atish.patra@wdc.com,
        Christoph Hellwig <hch@infradead.org>,
        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
        anup@brainfault.org
From:   Palmer Dabbelt <palmer@sifive.com>
To:     anup@brainfault.org
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On Sun, 11 Nov 2018 21:55:15 PST (-0800), anup@brainfault.org wrote:
> This patch extends Linux RISC-V build system to build and install:
> Image - Flat uncompressed kernel image
> Image.gz - Flat and GZip compressed kernel image
>
> Quiet a few bootloaders (such as Uboot, UEFI, etc) are capable of
> booting flat and compressed kernel images. In case of Uboot, booting
> Image or Image.gz is achieved using bootm command.
>
> The flat and uncompressed kernel image (i.e. Image) is very useful
> in pre-silicon developent and testing because we can create back-door
> HEX files for RAM on FPGAs from Image.
>
> Signed-off-by: Anup Patel <anup@brainfault.org>
> ---
>  arch/riscv/Makefile             | 15 ++++++++-
>  arch/riscv/boot/.gitignore      |  2 ++
>  arch/riscv/boot/Makefile        | 33 ++++++++++++++++++
>  arch/riscv/boot/install.sh      | 60 +++++++++++++++++++++++++++++++++
>  arch/riscv/kernel/head.S        | 10 ++++++
>  arch/riscv/kernel/vmlinux.lds.S |  2 +-
>  6 files changed, 120 insertions(+), 2 deletions(-)
>  create mode 100644 arch/riscv/boot/.gitignore
>  create mode 100644 arch/riscv/boot/Makefile
>  create mode 100644 arch/riscv/boot/install.sh
>
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index d10146197533..d117a60362eb 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -71,10 +71,23 @@ KBUILD_CFLAGS += $(call cc-option,-mstrict-align)
>  # arch specific predefines for sparse
>  CHECKFLAGS += -D__riscv -D__riscv_xlen=$(BITS)
>
> +# Default target when executing plain make
> +boot		:= arch/riscv/boot
> +KBUILD_IMAGE	:= $(boot)/Image.gz
> +
>  head-y := arch/riscv/kernel/head.o
>
>  core-y += arch/riscv/kernel/ arch/riscv/mm/
>
>  libs-y += arch/riscv/lib/
>
> -all: vmlinux
> +all: Image.gz
> +
> +Image: vmlinux
> +	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
> +
> +Image.%: Image
> +	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
> +
> +zinstall install:
> +	$(Q)$(MAKE) $(build)=$(boot) $@
> diff --git a/arch/riscv/boot/.gitignore b/arch/riscv/boot/.gitignore
> new file mode 100644
> index 000000000000..8dab0bb6ae66
> --- /dev/null
> +++ b/arch/riscv/boot/.gitignore
> @@ -0,0 +1,2 @@
> +Image
> +Image.gz
> diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
> new file mode 100644
> index 000000000000..0990a9fdbe5d
> --- /dev/null
> +++ b/arch/riscv/boot/Makefile
> @@ -0,0 +1,33 @@
> +#
> +# arch/riscv/boot/Makefile
> +#
> +# This file is included by the global makefile so that you can add your own
> +# architecture-specific flags and dependencies.
> +#
> +# This file is subject to the terms and conditions of the GNU General Public
> +# License.  See the file "COPYING" in the main directory of this archive
> +# for more details.
> +#
> +# Copyright (C) 2018, Anup Patel.
> +# Author: Anup Patel <anup@brainfault.org>
> +#
> +# Based on the ia64 and arm64 boot/Makefile.
> +#
> +
> +OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
> +
> +targets := Image
> +
> +$(obj)/Image: vmlinux FORCE
> +	$(call if_changed,objcopy)
> +
> +$(obj)/Image.gz: $(obj)/Image FORCE
> +	$(call if_changed,gzip)
> +
> +install:
> +	$(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \
> +	$(obj)/Image System.map "$(INSTALL_PATH)"
> +
> +zinstall:
> +	$(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \
> +	$(obj)/Image.gz System.map "$(INSTALL_PATH)"
> diff --git a/arch/riscv/boot/install.sh b/arch/riscv/boot/install.sh
> new file mode 100644
> index 000000000000..18c39159c0ff
> --- /dev/null
> +++ b/arch/riscv/boot/install.sh
> @@ -0,0 +1,60 @@
> +#!/bin/sh
> +#
> +# arch/riscv/boot/install.sh
> +#
> +# This file is subject to the terms and conditions of the GNU General Public
> +# License.  See the file "COPYING" in the main directory of this archive
> +# for more details.
> +#
> +# Copyright (C) 1995 by Linus Torvalds
> +#
> +# Adapted from code in arch/i386/boot/Makefile by H. Peter Anvin
> +# Adapted from code in arch/i386/boot/install.sh by Russell King
> +#
> +# "make install" script for the RISC-V Linux port
> +#
> +# Arguments:
> +#   $1 - kernel version
> +#   $2 - kernel image file
> +#   $3 - kernel map file
> +#   $4 - default install path (blank if root directory)
> +#
> +
> +verify () {
> +	if [ ! -f "$1" ]; then
> +		echo ""                                                   1>&2
> +		echo " *** Missing file: $1"                              1>&2
> +		echo ' *** You need to run "make" before "make install".' 1>&2
> +		echo ""                                                   1>&2
> +		exit 1
> +	fi
> +}
> +
> +# Make sure the files actually exist
> +verify "$2"
> +verify "$3"
> +
> +# User may have a custom install script
> +if [ -x ~/bin/${INSTALLKERNEL} ]; then exec ~/bin/${INSTALLKERNEL} "$@"; fi
> +if [ -x /sbin/${INSTALLKERNEL} ]; then exec /sbin/${INSTALLKERNEL} "$@"; fi
> +
> +if [ "$(basename $2)" = "Image.gz" ]; then
> +# Compressed install
> +  echo "Installing compressed kernel"
> +  base=vmlinuz
> +else
> +# Normal install
> +  echo "Installing normal kernel"
> +  base=vmlinux
> +fi
> +
> +if [ -f $4/$base-$1 ]; then
> +  mv $4/$base-$1 $4/$base-$1.old
> +fi
> +cat $2 > $4/$base-$1
> +
> +# Install system map file
> +if [ -f $4/System.map-$1 ]; then
> +  mv $4/System.map-$1 $4/System.map-$1.old
> +fi
> +cp $3 $4/System.map-$1
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 711190d473d4..fe884cd69abd 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -44,6 +44,16 @@ ENTRY(_start)
>  	amoadd.w a3, a2, (a3)
>  	bnez a3, .Lsecondary_start
>
> +	/* Clear BSS for flat non-ELF images */
> +	la a3, __bss_start
> +	la a4, __bss_stop
> +	ble a4, a3, clear_bss_done
> +clear_bss:
> +	REG_S zero, (a3)
> +	add a3, a3, RISCV_SZPTR
> +	blt a3, a4, clear_bss
> +clear_bss_done:
> +
>  	/* Save hart ID and DTB physical address */
>  	mv s0, a0
>  	mv s1, a1
> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> index ece84991609c..65df1dfdc303 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -74,7 +74,7 @@ SECTIONS
>  		*(.sbss*)
>  	}
>
> -	BSS_SECTION(0, 0, 0)
> +	BSS_SECTION(PAGE_SIZE, PAGE_SIZE, 0)

What does this do?

>
>  	EXCEPTION_TABLE(0x10)
>  	NOTES

Thanks!  I'm going to target this for the RCs as well: it's technically a new 
feature, but it seems pretty safe -- assuming the BSS_SECTION change can be 
explained to me :)