[PATCH v2 16/16] riscv: boot: add Image.xz support

[Lasse Collin]

The Image.* targets existed for other compressors already. Bootloader
support is needed for decompression.

This is for CONFIG_EFI_ZBOOT=n. With CONFIG_EFI_ZBOOT=y, XZ was already
available.

Comparision with Linux 6.10 RV64GC tinyconfig (in KiB):

    1027 Image
     594 Image.gz
     541 Image.zst
     510 Image.lzma
     474 Image.xz

Cc: Paul Walmsley <paul.walmsley at sifive.com>
Cc: Palmer Dabbelt <palmer at dabbelt.com>
Cc: Albert Ou <aou at eecs.berkeley.edu>
Cc: Jules Maselbas <jmaselbas at zdiv.net>
Cc: linux-riscv at lists.infradead.org
Signed-off-by: Lasse Collin <lasse.collin at tukaani.org>
---
 arch/riscv/Kconfig       | 1 +
 arch/riscv/Makefile      | 6 ++++--
 arch/riscv/boot/Makefile | 3 +++
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 736457a5898a..ef6a603b80c5 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -153,6 +153,7 @@ config RISCV
 	select HAVE_KERNEL_LZO if !XIP_KERNEL && !EFI_ZBOOT
 	select HAVE_KERNEL_UNCOMPRESSED if !XIP_KERNEL && !EFI_ZBOOT
 	select HAVE_KERNEL_ZSTD if !XIP_KERNEL && !EFI_ZBOOT
+	select HAVE_KERNEL_XZ if !XIP_KERNEL && !EFI_ZBOOT
 	select HAVE_KPROBES if !XIP_KERNEL
 	select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL
 	select HAVE_KRETPROBES if !XIP_KERNEL
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 6fe682139d2e..d469db9f46f4 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -159,6 +159,7 @@ boot-image-$(CONFIG_KERNEL_LZ4)		:= Image.lz4
 boot-image-$(CONFIG_KERNEL_LZMA)	:= Image.lzma
 boot-image-$(CONFIG_KERNEL_LZO)		:= Image.lzo
 boot-image-$(CONFIG_KERNEL_ZSTD)	:= Image.zst
+boot-image-$(CONFIG_KERNEL_XZ)		:= Image.xz
 ifdef CONFIG_RISCV_M_MODE
 boot-image-$(CONFIG_ARCH_CANAAN)	:= loader.bin
 endif
@@ -183,12 +184,12 @@ endif
 vdso-install-y			+= arch/riscv/kernel/vdso/vdso.so.dbg
 vdso-install-$(CONFIG_COMPAT)	+= arch/riscv/kernel/compat_vdso/compat_vdso.so.dbg
 
-BOOT_TARGETS := Image Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst loader loader.bin xipImage vmlinuz.efi
+BOOT_TARGETS := Image Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst Image.xz loader loader.bin xipImage vmlinuz.efi
 
 all:	$(notdir $(KBUILD_IMAGE))
 
 loader.bin: loader
-Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst loader xipImage vmlinuz.efi: Image
+Image.gz Image.bz2 Image.lz4 Image.lzma Image.lzo Image.zst Image.xz loader xipImage vmlinuz.efi: Image
 
 $(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
@@ -225,6 +226,7 @@ define archhelp
   echo  '  Image.lzma	- Compressed kernel image (arch/riscv/boot/Image.lzma)'
   echo  '  Image.lzo	- Compressed kernel image (arch/riscv/boot/Image.lzo)'
   echo  '  Image.zst	- Compressed kernel image (arch/riscv/boot/Image.zst)'
+  echo  '  Image.xz	- Compressed kernel image (arch/riscv/boot/Image.xz)'
   echo  '  vmlinuz.efi	- Compressed EFI kernel image (arch/riscv/boot/vmlinuz.efi)'
   echo  '		  Default when CONFIG_EFI_ZBOOT=y'
   echo  '  xipImage	- Execute-in-place kernel image (arch/riscv/boot/xipImage)'
diff --git a/arch/riscv/boot/Makefile b/arch/riscv/boot/Makefile
index 869c0345b908..710a5f6caf96 100644
--- a/arch/riscv/boot/Makefile
+++ b/arch/riscv/boot/Makefile
@@ -65,6 +65,9 @@ $(obj)/Image.lzo: $(obj)/Image FORCE
 $(obj)/Image.zst: $(obj)/Image FORCE
 	$(call if_changed,zstd)
 
+$(obj)/Image.xz: $(obj)/Image FORCE
+	$(call if_changed,xzkern)
+
 $(obj)/loader.bin: $(obj)/loader FORCE
 	$(call if_changed,objcopy)
 
-- 
2.45.2