Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754376AbdDDTOn (ORCPT ); Tue, 4 Apr 2017 15:14:43 -0400 Received: from mail-io0-f173.google.com ([209.85.223.173]:34303 "EHLO mail-io0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753845AbdDDTOl (ORCPT ); Tue, 4 Apr 2017 15:14:41 -0400 MIME-Version: 1.0 In-Reply-To: <1491295954-124682-1-git-send-email-chao.p.peng@linux.intel.com> References: <1491295954-124682-1-git-send-email-chao.p.peng@linux.intel.com> From: Kees Cook Date: Tue, 4 Apr 2017 12:14:39 -0700 X-Google-Sender-Auth: kzFvqqycYqfgGFlvtJj2yxlRoVk Message-ID: Subject: Re: [PATCH v2] x86/boot: Support uncompressed kernel To: Chao Peng Cc: "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , "x86@kernel.org" , Michal Marek , Yinghai Lu , Baoquan He , Jiri Kosina , "H.J. Lu" , Paul Bolle , Masahiro Yamada , Borislav Petkov , Andrew Morton , Arnd Bergmann , Petr Mladek , "David S. Miller" , "Paul E. McKenney" , Andy Lutomirski , Thomas Garnier , Nicolas Pitre , Tejun Heo , Daniel Mack , Sebastian Andrzej Siewior , Sergey Senozhatsky , Helge Deller , Rik van Riel , LKML , linux-kbuild Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7894 Lines: 216 On Tue, Apr 4, 2017 at 1:52 AM, Chao Peng wrote: > Compressed kernel has its own drawback: decompressing takes time. Even > though the time is short enough to ignore for most cases but for cases when > time is critical decompressing time still matters. > > The patch adds a 'CONFIG_KERNEL_RAW' configure choice so the built binary > can have no decompressing at all. The experiment shows: > > kernel kernel size time in decompress_kernel > compressed (gzip) 3.3M 53ms > compressed (lz4) 4.5M 16ms > uncompressed 14M 2ms > > Signed-off-by: Chao Peng > --- > v2: > * add HAVE_KERNEL_RAW > * decode ELF kernel in place instead of getting another copy > * minor comment fix > --- > arch/x86/Kconfig | 1 + > arch/x86/boot/compressed/Makefile | 3 +++ > arch/x86/boot/compressed/misc.c | 18 +++++++++++++----- > init/Kconfig | 13 ++++++++++++- > scripts/Makefile.lib | 8 ++++++++ > 5 files changed, 37 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index cc98d5a..207695c 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -142,6 +142,7 @@ config X86 > select HAVE_KERNEL_LZ4 > select HAVE_KERNEL_LZMA > select HAVE_KERNEL_LZO > + select HAVE_KERNEL_RAW > select HAVE_KERNEL_XZ > select HAVE_KPROBES > select HAVE_KPROBES_ON_FTRACE > diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile > index 44163e8..ed366e1 100644 > --- a/arch/x86/boot/compressed/Makefile > +++ b/arch/x86/boot/compressed/Makefile > @@ -120,6 +120,8 @@ $(obj)/vmlinux.relocs: vmlinux FORCE > vmlinux.bin.all-y := $(obj)/vmlinux.bin > vmlinux.bin.all-$(CONFIG_X86_NEED_RELOCS) += $(obj)/vmlinux.relocs > > +$(obj)/vmlinux.bin.raw: $(vmlinux.bin.all-y) FORCE > + $(call if_changed,raw) > $(obj)/vmlinux.bin.gz: $(vmlinux.bin.all-y) FORCE > $(call if_changed,gzip) > $(obj)/vmlinux.bin.bz2: $(vmlinux.bin.all-y) FORCE > @@ -133,6 +135,7 @@ $(obj)/vmlinux.bin.lzo: $(vmlinux.bin.all-y) FORCE > $(obj)/vmlinux.bin.lz4: $(vmlinux.bin.all-y) FORCE > $(call if_changed,lz4) > > +suffix-$(CONFIG_KERNEL_RAW) := raw > suffix-$(CONFIG_KERNEL_GZIP) := gz > suffix-$(CONFIG_KERNEL_BZIP2) := bz2 > suffix-$(CONFIG_KERNEL_LZMA) := lzma > diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c > index b3c5a5f0..9791ca9 100644 > --- a/arch/x86/boot/compressed/misc.c > +++ b/arch/x86/boot/compressed/misc.c > @@ -51,6 +51,10 @@ > static int vidport; > static int lines, cols; > > +#ifdef CONFIG_KERNEL_RAW > +#include > +#endif > + > #ifdef CONFIG_KERNEL_GZIP > #include "../../../../lib/decompress_inflate.c" > #endif > @@ -265,7 +269,7 @@ static inline void handle_relocations(void *output, unsigned long output_len, > { } > #endif > > -static void parse_elf(void *output) > +static void parse_elf(void* buf, void *output) I think "buf" is too generic a name here. "input" would be better, IMO. > { > #ifdef CONFIG_X86_64 > Elf64_Ehdr ehdr; > @@ -277,7 +281,7 @@ static void parse_elf(void *output) > void *dest; > int i; > > - memcpy(&ehdr, output, sizeof(ehdr)); > + memcpy(&ehdr, buf, sizeof(ehdr)); > if (ehdr.e_ident[EI_MAG0] != ELFMAG0 || > ehdr.e_ident[EI_MAG1] != ELFMAG1 || > ehdr.e_ident[EI_MAG2] != ELFMAG2 || > @@ -292,7 +296,7 @@ static void parse_elf(void *output) > if (!phdrs) > error("Failed to allocate space for phdrs"); > > - memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum); > + memcpy(phdrs, buf + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum); > > for (i = 0; i < ehdr.e_phnum; i++) { > phdr = &phdrs[i]; > @@ -305,7 +309,7 @@ static void parse_elf(void *output) > #else > dest = (void *)(phdr->p_paddr); > #endif > - memmove(dest, output + phdr->p_offset, phdr->p_filesz); > + memmove(dest, buf + phdr->p_offset, phdr->p_filesz); With the renaming from "buf" to "input" this becomes much more comprehensible: the PT_LOAD segments from "input" are loaded into "output". However, does this mean that the RAW load uses parse_elf to move the kernel into place? Does this happen safely? If it's already safe, shouldn't we not need "input" at all, and leave this as-is, like how the decompressed kernel operate? > break; > default: /* Ignore other PT_* */ break; > } > @@ -401,10 +405,14 @@ asmlinkage __visible void *extract_kernel(void *rmode, memptr heap, > error("Destination virtual address changed when not relocatable"); > #endif > > +#ifdef CONFIG_KERNEL_RAW > + parse_elf(input_data, output); > +#else > debug_putstr("\nDecompressing Linux... "); > __decompress(input_data, input_len, NULL, NULL, output, output_len, > NULL, error); > - parse_elf(output); > + parse_elf(output, output); > +#endif We should continue to avoid #ifdef blocks like this when possible. I'd recommended C-style: if (!IS_ENABLED(CONFIG_KERNEL_RAW)) { debug_putstr("\nDecompressing Linux... "); __decompress(input_data, input_len, NULL, NULL, output, output_len, NULL, error); } else output = input_data; parse_elf(output); > handle_relocations(output, output_len, virt_addr); > debug_putstr("done.\nBooting the kernel.\n"); > return output; > diff --git a/init/Kconfig b/init/Kconfig > index a92f27d..b8926bb 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -109,6 +109,9 @@ config LOCALVERSION_AUTO > > which is done within the script "scripts/setlocalversion".) > > +config HAVE_KERNEL_RAW > + bool > + > config HAVE_KERNEL_GZIP > bool > > @@ -130,7 +133,7 @@ config HAVE_KERNEL_LZ4 > choice > prompt "Kernel compression mode" > default KERNEL_GZIP > - depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 > + depends on HAVE_KERNEL_RAW || HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 > help > The linux kernel is a kind of self-extracting executable. > Several compression algorithms are available, which differ > @@ -149,6 +152,14 @@ choice > > If in doubt, select 'gzip' > > +config KERNEL_RAW > + bool "RAW" > + depends on HAVE_KERNEL_RAW > + help > + No compression. It creates much bigger kernel and uses much more > + space (disk/memory) than other choices. It can be useful when > + decompression speed is the most concern while space matters less. > + > config KERNEL_GZIP > bool "Gzip" > depends on HAVE_KERNEL_GZIP > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib > index 0a07f90..8a8f9a9 100644 > --- a/scripts/Makefile.lib > +++ b/scripts/Makefile.lib > @@ -357,6 +357,14 @@ cmd_lz4 = (cat $(filter-out FORCE,$^) | \ > lz4c -l -c1 stdin stdout && $(call size_append, $(filter-out FORCE,$^))) > $@ || \ > (rm -f $@ ; false) > > +# RAW > +# --------------------------------------------------------------------------- > +quiet_cmd_raw = RAW $@ > +cmd_raw = (cat $(filter-out FORCE,$^) && \ > + $(call size_append, $(filter-out FORCE,$^))) > $@ || \ > + (rm -f $@ ; false) > + > + > # U-Boot mkimage > # --------------------------------------------------------------------------- > > -- > 1.8.3.1 > -Kees -- Kees Cook Pixel Security