[PATCH 09/17] riscv: provide a flat entry loader

[Christoph Hellwig]

This allows just loading the kernel at a pre-set address without
qemu going bonkers trying to map the ELF file.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 arch/riscv/Makefile        | 13 +++++++++----
 arch/riscv/boot/Makefile   |  7 ++++++-
 arch/riscv/boot/loader.S   |  8 ++++++++
 arch/riscv/boot/loader.lds | 14 ++++++++++++++
 4 files changed, 37 insertions(+), 5 deletions(-)
 create mode 100644 arch/riscv/boot/loader.S
 create mode 100644 arch/riscv/boot/loader.lds

diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 6b0741c9f348..69dbb6cb72f3 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -84,13 +84,18 @@ PHONY += vdso_install
 vdso_install:
        $(Q)$(MAKE) $(build)=arch/riscv/kernel/vdso $@
 
-all: Image.gz
+ifeq ($(CONFIG_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..32d2addeddba 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 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 b/arch/riscv/boot/loader.lds
new file mode 100644
index 000000000000..da9efd57bf44
--- /dev/null
+++ b/arch/riscv/boot/loader.lds
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+OUTPUT_ARCH(riscv)
+ENTRY(_start)
+
+SECTIONS
+{
+       . = 0x80000000;
+
+       .payload : {
+               *(.payload)
+               . = ALIGN(8);
+       }
+}
-- 
2.20.1