[PATCH 11/12] riscv: provide a flat image loader

Christoph Hellwig
2019-10-28T12:11:25Z

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>
Reviewed-by: Anup Patel <anup@brainfault.org>
---
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..433ccbcabb23 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 $(obj)/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