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Ian Campbell

2008-Feb-13 12:56 UTC

[PATCHv3 1/3] x86: use ELF format in compressed images.

This allows other boot loaders such as the Xen domain builder the
opportunity to extract the ELF file.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: virtualization@lists.linux-foundation.org
---
 Documentation/i386/boot.txt       |   18 ++++++++++++
 arch/x86/boot/Makefile            |   14 +++++++++
 arch/x86/boot/compressed/Makefile |    2 +-
 arch/x86/boot/compressed/misc.c   |   56 +++++++++++++++++++++++++++++++++++++
 arch/x86/boot/header.S            |    6 ++++
 5 files changed, 95 insertions(+), 1 deletions(-)

diff --git a/Documentation/i386/boot.txt b/Documentation/i386/boot.txt
index fc49b79..b5f5ba1 100644
--- a/Documentation/i386/boot.txt
+++ b/Documentation/i386/boot.txt
@@ -170,6 +170,8 @@ Offset	Proto	Name		Meaning
 0238/4	2.06+	cmdline_size	Maximum size of the kernel command line
 023C/4	2.07+	hardware_subarch Hardware subarchitecture
 0240/8	2.07+	hardware_subarch_data Subarchitecture-specific data
+0248/4	2.08+	compressed_payload_offset
+024C/4	2.08+	compressed_payload_length
 
 (1) For backwards compatibility, if the setup_sects field contains 0, the
     real value is 4.
@@ -512,6 +514,22 @@ Protocol:	2.07+
 
   A pointer to data that is specific to hardware subarch
 
+Field name:	compressed_payload_offset
+Type:		read
+Offset/size:	0x248/4
+Protocol:	2.08+
+
+  If non-zero then this field contains the offset from the end of the
+  real-mode code to the compressed payload. The compression format
+  should be determined using the standard magic number, currently only
+  gzip is used.
+  
+Field name:	compressed_payload_length
+Type:		read
+Offset/size:	0x24c/4
+Protocol:	2.08+
+
+  The length of the compressed payload.
 
 **** THE KERNEL COMMAND LINE
 
diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index f88458e..9695aff 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -94,6 +94,20 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
 
 SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
 
+sed-offsets := -e 's/^00*/0/' \
+        -e 's/^\([0-9a-fA-F]*\) . \(input_data\|input_data_end\)$$/\#define
\2 0x\1/p'
+
+quiet_cmd_offsets = OFFSETS $@
+      cmd_offsets = $(NM) $< | sed -n $(sed-offsets) > $@
+
+$(obj)/offsets.h: $(obj)/compressed/vmlinux FORCE
+	$(call if_changed,offsets)
+
+targets += offsets.h
+
+AFLAGS_header.o += -I$(obj)
+$(obj)/header.o: $(obj)/offsets.h
+
 LDFLAGS_setup.elf	:= -T
 $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
 	$(call if_changed,ld)
diff --git a/arch/x86/boot/compressed/Makefile
b/arch/x86/boot/compressed/Makefile
index d2b9f3b..92fdd35 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -22,7 +22,7 @@ $(obj)/vmlinux: $(src)/vmlinux_$(BITS).lds
$(obj)/head_$(BITS).o $(obj)/misc.o $
 	$(call if_changed,ld)
 	@:
 
-OBJCOPYFLAGS_vmlinux.bin := -O binary -R .note -R .comment -S
+OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
 $(obj)/vmlinux.bin: vmlinux FORCE
 	$(call if_changed,objcopy)
 
diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c
index 8182e32..69aec2f 100644
--- a/arch/x86/boot/compressed/misc.c
+++ b/arch/x86/boot/compressed/misc.c
@@ -15,6 +15,10 @@
  * we just keep it from happening
  */
 #undef CONFIG_PARAVIRT
+#ifdef CONFIG_X86_32
+#define _ASM_DESC_H_ 1
+#endif
+
 #ifdef CONFIG_X86_64
 #define _LINUX_STRING_H_ 1
 #define __LINUX_BITMAP_H 1
@@ -22,6 +26,7 @@
 
 #include <linux/linkage.h>
 #include <linux/screen_info.h>
+#include <linux/elf.h>
 #include <asm/io.h>
 #include <asm/page.h>
 #include <asm/boot.h>
@@ -365,6 +370,56 @@ static void error(char *x)
 		asm("hlt");
 }
 
+static void parse_elf(void *output)
+{
+#ifdef CONFIG_X86_64
+	Elf64_Ehdr ehdr;
+	Elf64_Phdr *phdrs, *phdr;
+#else
+	Elf32_Ehdr ehdr;
+	Elf32_Phdr *phdrs, *phdr;
+#endif
+	void *dest;
+	int i;
+
+	memcpy(&ehdr, output, sizeof(ehdr));
+	if(ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
+	   ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
+	   ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
+	   ehdr.e_ident[EI_MAG3] != ELFMAG3)
+	{
+		error("Kernel is not a valid ELF file");
+		return;
+	}
+
+	putstr("Parsing ELF... ");
+
+	phdrs = malloc(sizeof(*phdrs) * ehdr.e_phnum);
+	if (!phdrs)
+		error("Failed to allocate space for phdrs");
+
+	memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) * ehdr.e_phnum);
+
+	for (i=0; i<ehdr.e_phnum; i++) {
+		phdr = &phdrs[i];
+
+		switch (phdr->p_type) {
+		case PT_LOAD:
+#ifdef CONFIG_RELOCATABLE
+			dest = output;
+			dest += (phdr->p_paddr - LOAD_PHYSICAL_ADDR);
+#else
+			dest = (void*)(phdr->p_paddr);
+#endif
+			memcpy(dest,
+			       output + phdr->p_offset,
+			       phdr->p_filesz);
+			break;
+		default: /* Ignore other PT_* */ break;
+		}
+	}
+}
+
 asmlinkage void decompress_kernel(void *rmode, memptr heap,
 				  uch *input_data, unsigned long input_len,
 				  uch *output)
@@ -408,6 +463,7 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap,
 	makecrc();
 	putstr("\nDecompressing Linux... ");
 	gunzip();
+	parse_elf(output);
 	putstr("done.\nBooting the kernel.\n");
 	return;
 }
diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 64ad901..8471658 100644
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -22,6 +22,7 @@
 #include <asm/page.h>
 #include <asm/setup.h>
 #include "boot.h"
+#include "offsets.h"
 
 SETUPSECTS	= 4			/* default nr of setup-sectors */
 BOOTSEG		= 0x07C0		/* original address of boot-sector */
@@ -223,6 +224,11 @@ hardware_subarch:	.long 0			# subarchitecture, added with
2.07
 
 hardware_subarch_data:	.quad 0
 
+compressed_payload_offset:
+			.long input_data
+compressed_payload_length:
+			.long input_data_end-input_data
+
 # End of setup header #####################################################
 
 	.section ".inittext", "ax"
-- 
1.5.4

Mark McLoughlin

2008-Feb-14 11:34 UTC

head link

[PATCHv3 1/3] x86: use ELF format in compressed images.

On Wed, 2008-02-13 at 20:54 +0000, Ian Campbell wrote:> This allows other boot loaders such as the Xen domain builder the
> opportunity to extract the ELF file.
	Right, Xen currently can't boot bzImage (it needs the ELF image) so you
still can't use the same kernel image on Xen as bare-metal.
> +Field name:	compressed_payload_offset
> +Type:		read
> +Offset/size:	0x248/4
> +Protocol:	2.08+
> +
> +  If non-zero then this field contains the offset from the end of the
> +  real-mode code to the compressed payload. The compression format
> +  should be determined using the standard magic number, currently only
> +  gzip is used.
	Should probably mention that the payload format is expected to be ELF.
 > diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
> index f88458e..9695aff 100644
> --- a/arch/x86/boot/Makefile
> +++ b/arch/x86/boot/Makefile
> @@ -94,6 +94,20 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
>  
>  SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
>  
> +sed-offsets := -e 's/^00*/0/' \
> +        -e 's/^\([0-9a-fA-F]*\) .
\(input_data\|input_data_end\)$$/\#define \2 0x\1/p'
> +
> +quiet_cmd_offsets = OFFSETS $@
> +      cmd_offsets = $(NM) $< | sed -n $(sed-offsets) > $@
> +
> +$(obj)/offsets.h: $(obj)/compressed/vmlinux FORCE
> +	$(call if_changed,offsets)
> +
> +targets += offsets.h
> +
> +AFLAGS_header.o += -I$(obj)
> +$(obj)/header.o: $(obj)/offsets.h
	How about this?

+sed-offsets := -e 's/^00*/0/' \
+        -e 's/^\([0-9a-fA-F]*\) .
\(input_data\|input_data_end\)$$/-D\2=0x\1 /p'
+
+$(obj)/header.o: AFLAGS_header.o += $(shell $(NM) $(obj)/compressed/vmlinux |
sed -n $(sed-offsets))
+$(obj)/header.o: $(obj)/compressed/vmlinux FORCE

Cheers,
Mark.

Yinghai Lu

2008-Apr-06 07:03 UTC

head link

[PATCHv3 1/3] x86: use ELF format in compressed images.

On Wed, Feb 13, 2008 at 1:54 PM, Ian Campbell <ijc at hellion.org.uk>
wrote:> This allows other boot loaders such as the Xen domain builder the
>  opportunity to extract the ELF file.
>
>  Signed-off-by: Ian Campbell <ijc at hellion.org.uk>
>  Cc: Thomas Gleixner <tglx at linutronix.de>
>  Cc: Ingo Molnar <mingo at redhat.com>
>  Cc: H. Peter Anvin <hpa at zytor.com>
>  Cc: Jeremy Fitzhardinge <jeremy at goop.org>
>  Cc: virtualization at lists.linux-foundation.org
>  ---
>   Documentation/i386/boot.txt       |   18 ++++++++++++
>   arch/x86/boot/Makefile            |   14 +++++++++
>   arch/x86/boot/compressed/Makefile |    2 +-
>   arch/x86/boot/compressed/misc.c   |   56
+++++++++++++++++++++++++++++++++++++
>   arch/x86/boot/header.S            |    6 ++++
>   5 files changed, 95 insertions(+), 1 deletions(-)
>
>  diff --git a/Documentation/i386/boot.txt b/Documentation/i386/boot.txt
>  index fc49b79..b5f5ba1 100644
>  --- a/Documentation/i386/boot.txt
>  +++ b/Documentation/i386/boot.txt
>  @@ -170,6 +170,8 @@ Offset      Proto   Name            Meaning
>   0238/4 2.06+   cmdline_size    Maximum size of the kernel command line
>   023C/4 2.07+   hardware_subarch Hardware subarchitecture
>   0240/8 2.07+   hardware_subarch_data Subarchitecture-specific data
>  +0248/4 2.08+   compressed_payload_offset
>  +024C/4 2.08+   compressed_payload_length
>
>   (1) For backwards compatibility, if the setup_sects field contains 0, the
>      real value is 4.
>  @@ -512,6 +514,22 @@ Protocol:  2.07+
>
>    A pointer to data that is specific to hardware subarch
>
>  +Field name:    compressed_payload_offset
>  +Type:          read
>  +Offset/size:   0x248/4
>  +Protocol:      2.08+
>  +
>  +  If non-zero then this field contains the offset from the end of the
>  +  real-mode code to the compressed payload. The compression format
>  +  should be determined using the standard magic number, currently only
>  +  gzip is used.
>  +
>  +Field name:    compressed_payload_length
>  +Type:          read
>  +Offset/size:   0x24c/4
>  +Protocol:      2.08+
>  +
>  +  The length of the compressed payload.
>
>   **** THE KERNEL COMMAND LINE
>
>  diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
>  index f88458e..9695aff 100644
>  --- a/arch/x86/boot/Makefile
>  +++ b/arch/x86/boot/Makefile
>  @@ -94,6 +94,20 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
>
>   SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
>
>  +sed-offsets := -e 's/^00*/0/' \
>  +        -e 's/^\([0-9a-fA-F]*\) .
\(input_data\|input_data_end\)$$/\#define \2 0x\1/p'
>  +
>  +quiet_cmd_offsets = OFFSETS $@
>  +      cmd_offsets = $(NM) $< | sed -n $(sed-offsets) > $@
>  +
>  +$(obj)/offsets.h: $(obj)/compressed/vmlinux FORCE
>  +       $(call if_changed,offsets)
>  +
>  +targets += offsets.h
>  +
>  +AFLAGS_header.o += -I$(obj)
>  +$(obj)/header.o: $(obj)/offsets.h
>  +
>   LDFLAGS_setup.elf      := -T
>   $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE
>         $(call if_changed,ld)
>  diff --git a/arch/x86/boot/compressed/Makefile
b/arch/x86/boot/compressed/Makefile
>  index d2b9f3b..92fdd35 100644
>  --- a/arch/x86/boot/compressed/Makefile
>  +++ b/arch/x86/boot/compressed/Makefile
>  @@ -22,7 +22,7 @@ $(obj)/vmlinux: $(src)/vmlinux_$(BITS).lds
$(obj)/head_$(BITS).o $(obj)/misc.o $
>         $(call if_changed,ld)
>         @:
>
>  -OBJCOPYFLAGS_vmlinux.bin := -O binary -R .note -R .comment -S
>  +OBJCOPYFLAGS_vmlinux.bin :=  -R .comment -S
>   $(obj)/vmlinux.bin: vmlinux FORCE
>         $(call if_changed,objcopy)
>
>  diff --git a/arch/x86/boot/compressed/misc.c
b/arch/x86/boot/compressed/misc.c
>  index 8182e32..69aec2f 100644
>  --- a/arch/x86/boot/compressed/misc.c
>  +++ b/arch/x86/boot/compressed/misc.c
>  @@ -15,6 +15,10 @@
>   * we just keep it from happening
>   */
>   #undef CONFIG_PARAVIRT
>  +#ifdef CONFIG_X86_32
>  +#define _ASM_DESC_H_ 1
>  +#endif
>  +
>   #ifdef CONFIG_X86_64
>   #define _LINUX_STRING_H_ 1
>   #define __LINUX_BITMAP_H 1
>  @@ -22,6 +26,7 @@
>
>   #include <linux/linkage.h>
>   #include <linux/screen_info.h>
>  +#include <linux/elf.h>
>   #include <asm/io.h>
>   #include <asm/page.h>
>   #include <asm/boot.h>
>  @@ -365,6 +370,56 @@ static void error(char *x)
>                 asm("hlt");
>   }
>
>  +static void parse_elf(void *output)
>  +{
>  +#ifdef CONFIG_X86_64
>  +       Elf64_Ehdr ehdr;
>  +       Elf64_Phdr *phdrs, *phdr;
>  +#else
>  +       Elf32_Ehdr ehdr;
>  +       Elf32_Phdr *phdrs, *phdr;
>  +#endif
>  +       void *dest;
>  +       int i;
>  +
>  +       memcpy(&ehdr, output, sizeof(ehdr));
>  +       if(ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
>  +          ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
>  +          ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
>  +          ehdr.e_ident[EI_MAG3] != ELFMAG3)
>  +       {
>  +               error("Kernel is not a valid ELF file");
>  +               return;
>  +       }
>  +
>  +       putstr("Parsing ELF... ");
>  +
>  +       phdrs = malloc(sizeof(*phdrs) * ehdr.e_phnum);
>  +       if (!phdrs)
>  +               error("Failed to allocate space for phdrs");
>  +
>  +       memcpy(phdrs, output + ehdr.e_phoff, sizeof(*phdrs) *
ehdr.e_phnum);
>  +
>  +       for (i=0; i<ehdr.e_phnum; i++) {
>  +               phdr = &phdrs[i];
>  +
>  +               switch (phdr->p_type) {
>  +               case PT_LOAD:
>  +#ifdef CONFIG_RELOCATABLE
>  +                       dest = output;
>  +                       dest += (phdr->p_paddr - LOAD_PHYSICAL_ADDR);
>  +#else
>  +                       dest = (void*)(phdr->p_paddr);
>  +#endif
>  +                       memcpy(dest,
>  +                              output + phdr->p_offset,
>  +                              phdr->p_filesz);
>  +                       break;
so will cost every bzImage extra memory copy? that could be 18M or
even more big.

wonder if can have one some other kind elf format, and offset load
address to avoid that mem copy.

YH

Ian Campbell

2008-Apr-06 10:22 UTC

head link

[PATCHv3 1/3] x86: use ELF format in compressed images.

On Sun, 2008-04-06 at 00:03 -0700, Yinghai Lu wrote:> so will cost every bzImage extra memory copy? that could be 18M or
> even more big.
Is it a huge deal for something that happens exactly once on boot? How
does the time take compare with the time to do the decompression?

18M seems like an awfully large kernel image to me. My distro (Debian)
kernel is more like 3M uncompressed. If someone was interested in fast
booting presumably they would either build a kernel with exactly what
they need.
> wonder if can have one some other kind elf format, and offset load
> address to avoid that mem copy.
I guess you could reduce the load address by sizeof(headers) and add a
dest == (output + phdr->p_offset) test before the copy.

Another possibility, which is much more complex, is that the ELF parsing
could be integrated into the decompressor such that the data is
decompressed into the correct location directly.

Ian.

-- 
Ian Campbell

People who have no faults are terrible; there is no way of taking
advantage of them.
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H. Peter Anvin

2008-Apr-06 16:38 UTC

head link

[PATCHv3 1/3] x86: use ELF format in compressed images.

Yinghai Lu wrote:> so will cost every bzImage extra memory copy? that could be 18M or
> even more big.
I wouldn't worry about that.  You will typically have several copies of 
the images during the execution of the boot loader.

	-hpa

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