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Peter Anvin" , Masahiro Yamada , Nathan Chancellor , Nicolas Schier Cc: Ard Biesheuvel , linux-efi@vger.kernel.org, Andrew Morton , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Jann Horn X-Mailer: b4 0.15-dev X-Developer-Signature: v=1; a=ed25519-sha256; t=1737497773; l=5794; i=jannh@google.com; s=20240730; h=from:subject:message-id; bh=kuS9+usQUnoAJ7h3I+IY6V/rxzIi2s09XeV3LdJfMj4=; b=vFk+qsZp8iDibxHFL/PkhT2fOb37LGRH19Iyz9tA2NghkFd8EcF3616hnZCM3I52KXUPZrI3s Jo5gw+7fi1PBsepq8YqzxMUxrU4ZYo7v/qp55xb5Z4kegUMb2Sy/6uF X-Developer-Key: i=jannh@google.com; a=ed25519; pk=AljNtGOzXeF6khBXDJVVvwSEkVDGnnZZYqfWhP1V+C8= Support storing the kernel uncompressed for developers who want to quickly iterate with one-off kernel builds. Store it in the usual format with a 4-byte length suffix and keep this new codepath as close as possible to the normal path where decompression happens. The other compression methods offered by the kernel take some time; even LZ4 (which the kernel uses at compression level 9) takes ~2.8 seconds to compress a 110M large vmlinux.bin on my machine. An alternate approach to this would be to offer customization of the LZ4 compression level through a kconfig variable; and yet another approach would be to abuse the existing gzip decompression logic by storing the kernel as "non-compressed" DEFLATE blocks, so that the decompression code will essentially end up just doing a bunch of memcpy() calls. Signed-off-by: Jann Horn --- arch/x86/Kconfig | 1 + arch/x86/boot/compressed/Makefile | 3 +++ arch/x86/boot/compressed/misc.c | 4 ++++ arch/x86/boot/header.S | 2 ++ drivers/firmware/efi/libstub/zboot.c | 2 ++ lib/decompress_dummy.c | 15 +++++++++++++++ scripts/Makefile.lib | 3 +++ 7 files changed, 30 insertions(+) --- base-commit: 95ec54a420b8f445e04a7ca0ea8deb72c51fe1d3 change-id: 20250121-kernel-compress-fast-350ce5801c28 diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index ef6cfea9df7333c52e331f487a0b29f037a6bf14..6d468d47861ae0b6ec6b7649af6ab4dd123eb5c8 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -250,6 +250,7 @@ config X86 select HAVE_KERNEL_LZO select HAVE_KERNEL_XZ select HAVE_KERNEL_ZSTD + select HAVE_KERNEL_UNCOMPRESSED select HAVE_KPROBES select HAVE_KPROBES_ON_FTRACE select HAVE_FUNCTION_ERROR_INJECTION diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile index f2051644de9432e3466ac0ef1c4d3abc378e37d3..06079e02d9e01704cc0da06c1195854c8d0602ac 100644 --- a/arch/x86/boot/compressed/Makefile +++ b/arch/x86/boot/compressed/Makefile @@ -137,6 +137,8 @@ $(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE $(call if_changed,lz4_with_size) $(obj)/vmlinux.bin.zst: $(vmlinux.bin.all-y) FORCE $(call if_changed,zstd22_with_size) +$(obj)/vmlinux.bin.store: $(vmlinux.bin.all-y) FORCE + $(call if_changed,store_with_size) suffix-$(CONFIG_KERNEL_GZIP) := gz suffix-$(CONFIG_KERNEL_BZIP2) := bz2 @@ -145,6 +147,7 @@ suffix-$(CONFIG_KERNEL_XZ) := xz suffix-$(CONFIG_KERNEL_LZO) := lzo suffix-$(CONFIG_KERNEL_LZ4) := lz4 suffix-$(CONFIG_KERNEL_ZSTD) := zst +suffix-$(CONFIG_KERNEL_UNCOMPRESSED) := store quiet_cmd_mkpiggy = MKPIGGY $@ cmd_mkpiggy = $(obj)/mkpiggy $< > $@ diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 0d37420cad0259554f8160dea0c502cb7e2fc6cd..5d514a147d5d1ae252419e4c7cdc09e9c29f110f 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -88,6 +88,10 @@ static int cols __section(".data"); #ifdef CONFIG_KERNEL_ZSTD #include "../../../../lib/decompress_unzstd.c" #endif + +#ifdef CONFIG_KERNEL_UNCOMPRESSED +#include "../../../../lib/decompress_dummy.c" +#endif /* * NOTE: When adding a new decompressor, please update the analysis in * ../header.S. diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index b5c79f43359bcde2c4c3c5ed796e8780f7979774..8397470231cf571a33ac75f7ca7020608e170eef 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -483,6 +483,8 @@ pref_address: .quad LOAD_PHYSICAL_ADDR # preferred load addr # larger margin. # # extra_bytes = (uncompressed_size >> 8) + 131072 +# +# Uncompressed data does not grow. #define ZO_z_extra_bytes ((ZO_z_output_len >> 8) + 131072) #if ZO_z_output_len > ZO_z_input_len diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c index af23b3c502282f9bd644c38af445875c225cdf42..1c43a6ae5e665aa3bff3bd467c8a2f5525b1a6e9 100644 --- a/drivers/firmware/efi/libstub/zboot.c +++ b/drivers/firmware/efi/libstub/zboot.c @@ -27,6 +27,8 @@ static unsigned long free_mem_ptr, free_mem_end_ptr; #include "../../../../lib/decompress_unxz.c" #elif defined(CONFIG_KERNEL_ZSTD) #include "../../../../lib/decompress_unzstd.c" +#elif defined(CONFIG_KERNEL_UNCOMPRESSED) +#include "../../../../lib/decompress_dummy.c" #endif extern char efi_zboot_header[]; diff --git a/lib/decompress_dummy.c b/lib/decompress_dummy.c new file mode 100644 index 0000000000000000000000000000000000000000..49435e199a07f6ed376ff93adeae8ee08a9dd3d7 --- /dev/null +++ b/lib/decompress_dummy.c @@ -0,0 +1,15 @@ +// SPDX-License-Identifier: GPL-2.0 +STATIC int INIT __decompress(unsigned char *buf, long len, + long (*fill)(void*, unsigned long), + long (*flush)(void*, unsigned long), + unsigned char *out_buf, long out_len, + long *pos, + void (*error)(char *x)) +{ + if (out_len < len-4) { + error("output buffer too small"); + return -1; + } + memcpy(out_buf, buf, len-4); + return 0; +} diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib index 7395200538da89a2f6e6d21f8959f3f60d291d79..bb8116ba8ba189d5246fcb0e71c7be6e05ce5148 100644 --- a/scripts/Makefile.lib +++ b/scripts/Makefile.lib @@ -525,6 +525,9 @@ quiet_cmd_zstd22 = ZSTD22 $@ quiet_cmd_zstd22_with_size = ZSTD22 $@ cmd_zstd22_with_size = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@ +quiet_cmd_store_with_size = STORE $@ + cmd_store_with_size = { cat $(real-prereqs); $(size_append); } > $@ + # ASM offsets # ---------------------------------------------------------------------------