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authorArd Biesheuvel <ardb@kernel.org>2024-12-06 11:41:40 +0100
committerArd Biesheuvel <ardb@kernel.org>2024-12-06 16:59:56 +0100
commit0b2c29fb68f8bf3e87a9d88404aa6fdd486223e5 (patch)
treef599c2b113be2d37f7b16c647042c3e7e4abd553 /drivers/firmware
parent40384c840ea1944d7c5a392e8975ed088ecf0b37 (diff)
efi/zboot: Limit compression options to GZIP and ZSTD
For historical reasons, the legacy decompressor code on various architectures supports 7 different compression types for the compressed kernel image. EFI zboot is not a compression library museum, and so the options can be limited to what is likely to be useful in practice: - GZIP is tried and tested, and is still one of the fastest at decompression time, although the compression ratio is not very high; moreover, Fedora is already shipping EFI zboot kernels for arm64 that use GZIP, and QEMU implements direct support for it when booting a kernel without firmware loaded; - ZSTD has a very high compression ratio (although not the highest), and is almost as fast as GZIP at decompression time. Reducing the number of options makes it less of a hassle for other consumers of the EFI zboot format (such as QEMU today, and kexec in the future) to support it transparently without having to carry 7 different decompression libraries. Acked-by: Gerd Hoffmann <kraxel@redhat.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Diffstat (limited to 'drivers/firmware')
-rw-r--r--drivers/firmware/efi/Kconfig4
-rw-r--r--drivers/firmware/efi/libstub/Makefile.zboot18
2 files changed, 6 insertions, 16 deletions
diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index e312d731f4a3..5fe61b9ab5f9 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -76,10 +76,6 @@ config EFI_ZBOOT
bool "Enable the generic EFI decompressor"
depends on EFI_GENERIC_STUB && !ARM
select HAVE_KERNEL_GZIP
- select HAVE_KERNEL_LZ4
- select HAVE_KERNEL_LZMA
- select HAVE_KERNEL_LZO
- select HAVE_KERNEL_XZ
select HAVE_KERNEL_ZSTD
help
Create the bootable image as an EFI application that carries the
diff --git a/drivers/firmware/efi/libstub/Makefile.zboot b/drivers/firmware/efi/libstub/Makefile.zboot
index 65ffd0b760b2..48842b5c106b 100644
--- a/drivers/firmware/efi/libstub/Makefile.zboot
+++ b/drivers/firmware/efi/libstub/Makefile.zboot
@@ -12,22 +12,16 @@ quiet_cmd_copy_and_pad = PAD $@
$(obj)/vmlinux.bin: $(obj)/$(EFI_ZBOOT_PAYLOAD) FORCE
$(call if_changed,copy_and_pad)
-comp-type-$(CONFIG_KERNEL_GZIP) := gzip
-comp-type-$(CONFIG_KERNEL_LZ4) := lz4
-comp-type-$(CONFIG_KERNEL_LZMA) := lzma
-comp-type-$(CONFIG_KERNEL_LZO) := lzo
-comp-type-$(CONFIG_KERNEL_XZ) := xzkern
-comp-type-$(CONFIG_KERNEL_ZSTD) := zstd22
-
# in GZIP, the appended le32 carrying the uncompressed size is part of the
# format, but in other cases, we just append it at the end for convenience,
# causing the original tools to complain when checking image integrity.
-# So disregard it when calculating the payload size in the zimage header.
-zboot-method-y := $(comp-type-y)_with_size
-zboot-size-len-y := 4
+comp-type-y := gzip
+zboot-method-y := gzip
+zboot-size-len-y := 0
-zboot-method-$(CONFIG_KERNEL_GZIP) := gzip
-zboot-size-len-$(CONFIG_KERNEL_GZIP) := 0
+comp-type-$(CONFIG_KERNEL_ZSTD) := zstd
+zboot-method-$(CONFIG_KERNEL_ZSTD) := zstd22_with_size
+zboot-size-len-$(CONFIG_KERNEL_ZSTD) := 4
$(obj)/vmlinuz: $(obj)/vmlinux.bin FORCE
$(call if_changed,$(zboot-method-y))