Re: [PATCH 14/15] riscv: provide a flat image loader

From: Anup Patel <anup@brainfault.org>
To: Christoph Hellwig <hch@lst.de>
Cc: "linux-kernel@vger.kernel.org List"
	<linux-kernel@vger.kernel.org>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	Palmer Dabbelt <palmer@sifive.com>,
	linux-riscv <linux-riscv@lists.infradead.org>,
	Paul Walmsley <paul.walmsley@sifive.com>
Subject: Re: [PATCH 14/15] riscv: provide a flat image loader
Date: Fri, 18 Oct 2019 08:36:33 +0530	[thread overview]
Message-ID: <CAAhSdy01FReApQOPY5B8jcZ34pyWaLpYok_+7G+hEvFKwhC4bQ@mail.gmail.com> (raw)
In-Reply-To: <20191017173743.5430-15-hch@lst.de>

On Thu, Oct 17, 2019 at 11:08 PM Christoph Hellwig <hch@lst.de> wrote:
>
> This allows just loading the kernel at a pre-set address without
> qemu going bonkers trying to map the ELF file.
>
> Contains a controbution from Aurabindo Jayamohanan to reuse the
> PAGE_OFFSET definition.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  arch/riscv/Makefile          | 13 +++++++++----
>  arch/riscv/boot/Makefile     |  7 ++++++-
>  arch/riscv/boot/loader.S     |  8 ++++++++
>  arch/riscv/boot/loader.lds.S | 16 ++++++++++++++++
>  4 files changed, 39 insertions(+), 5 deletions(-)
>  create mode 100644 arch/riscv/boot/loader.S
>  create mode 100644 arch/riscv/boot/loader.lds.S
>
> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
> index f5e914210245..b9009a2fbaf5 100644
> --- a/arch/riscv/Makefile
> +++ b/arch/riscv/Makefile
> @@ -83,13 +83,18 @@ PHONY += vdso_install
>  vdso_install:
>         $(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
>
> -all: Image.gz
> +ifeq ($(CONFIG_RISCV_M_MODE),y)
> +KBUILD_IMAGE := $(boot)/loader
> +else
> +KBUILD_IMAGE := $(boot)/Image.gz
> +endif
> +BOOT_TARGETS := Image Image.gz loader
>
> -Image: vmlinux
> -       $(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
> +all:   $(notdir $(KBUILD_IMAGE))
>
> -Image.%: Image
> +$(BOOT_TARGETS): vmlinux
>         $(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
> +       @$(kecho) '  Kernel: $(boot)/$@ is ready'
>
>  zinstall install:
>         $(Q)$(MAKE) $(build)=$(boot) $@
> diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
> index 0990a9fdbe5d..8639e0dd2cdf 100644
> --- a/arch/riscv/boot/Makefile
> +++ b/arch/riscv/boot/Makefile
> @@ -16,7 +16,7 @@
>
>  OBJCOPYFLAGS_Image :=-O binary -R .note -R .note.gnu.build-id -R .comment -S
>
> -targets := Image
> +targets := Image loader
>
>  $(obj)/Image: vmlinux FORCE
>         $(call if_changed,objcopy)
> @@ -24,6 +24,11 @@ $(obj)/Image: vmlinux FORCE
>  $(obj)/Image.gz: $(obj)/Image FORCE
>         $(call if_changed,gzip)
>
> +loader.o: $(src)/loader.S $(obj)/Image
> +
> +$(obj)/loader: $(obj)/loader.o $(obj)/Image $(obj)/loader.lds FORCE
> +       $(Q)$(LD) -T $(src)/loader.lds -o $@ $(obj)/loader.o
> +
>  install:
>         $(CONFIG_SHELL) $(srctree)/$(src)/install.sh $(KERNELRELEASE) \
>         $(obj)/Image System.map "$(INSTALL_PATH)"
> diff --git a/arch/riscv/boot/loader.S b/arch/riscv/boot/loader.S
> new file mode 100644
> index 000000000000..5586e2610dbb
> --- /dev/null
> +++ b/arch/riscv/boot/loader.S
> @@ -0,0 +1,8 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +       .align 4
> +       .section .payload, "ax", %progbits
> +       .globl _start
> +_start:
> +       .incbin "arch/riscv/boot/Image"
> +
> diff --git a/arch/riscv/boot/loader.lds.S b/arch/riscv/boot/loader.lds.S
> new file mode 100644
> index 000000000000..47a5003c2e28
> --- /dev/null
> +++ b/arch/riscv/boot/loader.lds.S
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <asm/page.h>
> +
> +OUTPUT_ARCH(riscv)
> +ENTRY(_start)
> +
> +SECTIONS
> +{
> +       . = PAGE_OFFSET;
> +
> +       .payload : {
> +               *(.payload)
> +               . = ALIGN(8);
> +       }
> +}
> --
> 2.20.1
>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup

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