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[Xen-changelog] [xen-unstable] [LINUX] Support creating ELF note segment

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Subject: [Xen-changelog] [xen-unstable] [LINUX] Support creating ELF note segments in the kernel ELF image.
From: Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 22 Aug 2006 16:00:47 +0000
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# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxxxxx>
# Node ID a4550b7488400c44a9f27c92115c8e364493837a
# Parent  cd4e7ace4e58d9e35c08ccaa4677c6b6d0cf137b
[LINUX] Support creating ELF note segments in the kernel ELF image.

i386 version is taken from 2.6.18-rc4-mm1 and x86_64 version has been
submitted for inclusion.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxxxxx>
---
 linux-2.6-xen-sparse/arch/i386/kernel/vmlinux.lds.S                            
          |   12 +
 patches/linux-2.6.16.13/series                                                 
          |    2 
 
patches/linux-2.6.16.13/x86-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
    |   70 ++++++++++
 
patches/linux-2.6.16.13/x86_64-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
 |   30 ++++
 4 files changed, 112 insertions(+), 2 deletions(-)

diff -r cd4e7ace4e58 -r a4550b748840 
linux-2.6-xen-sparse/arch/i386/kernel/vmlinux.lds.S
--- a/linux-2.6-xen-sparse/arch/i386/kernel/vmlinux.lds.S       Tue Aug 22 
11:34:46 2006 +0100
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/vmlinux.lds.S       Tue Aug 22 
12:20:43 2006 +0100
@@ -12,6 +12,12 @@ OUTPUT_ARCH(i386)
 OUTPUT_ARCH(i386)
 ENTRY(phys_startup_32)
 jiffies = jiffies_64;
+
+PHDRS {
+       text PT_LOAD FLAGS(5);  /* R_E */
+       data PT_LOAD FLAGS(7);  /* RWE */
+       note PT_NOTE FLAGS(4);  /* R__ */
+}
 SECTIONS
 {
   . = __KERNEL_START;
@@ -25,7 +31,7 @@ SECTIONS
        KPROBES_TEXT
        *(.fixup)
        *(.gnu.warning)
-       } = 0x9090
+       } :text = 0x9090
 
   _etext = .;                  /* End of text section */
 
@@ -47,7 +53,7 @@ SECTIONS
   .data : AT(ADDR(.data) - LOAD_OFFSET) {      /* Data */
        *(.data)
        CONSTRUCTORS
-       }
+       } :data
 
   . = ALIGN(4096);
   __nosave_begin = .;
@@ -154,4 +160,6 @@ SECTIONS
   STABS_DEBUG
 
   DWARF_DEBUG
+
+  NOTES
 }
diff -r cd4e7ace4e58 -r a4550b748840 patches/linux-2.6.16.13/series
--- a/patches/linux-2.6.16.13/series    Tue Aug 22 11:34:46 2006 +0100
+++ b/patches/linux-2.6.16.13/series    Tue Aug 22 12:20:43 2006 +0100
@@ -18,3 +18,5 @@ x86-increase-interrupt-vector-range.patc
 x86-increase-interrupt-vector-range.patch
 xen-hotplug.patch
 xenoprof-generic.patch
+x86-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
+x86_64-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
diff -r cd4e7ace4e58 -r a4550b748840 
patches/linux-2.6.16.13/x86-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ 
b/patches/linux-2.6.16.13/x86-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
     Tue Aug 22 12:20:43 2006 +0100
@@ -0,0 +1,174 @@
+Taken from 2.6.18-rc4-mm1.
+
+From: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
+
+This patch will pack any .note.* section into a PT_NOTE segment in the output
+file.
+
+To do this, we tell ld that we need a PT_NOTE segment.  This requires us to
+start explicitly mapping sections to segments, so we also need to explicitly
+create PT_LOAD segments for text and data, and map the sections to them
+appropriately.  Fortunately, each section will default to its previous
+section's segment, so it doesn't take many changes to vmlinux.lds.S.
+
+This only changes i386 for now, but I presume the corresponding changes for
+other architectures will be as simple.
+
+This change also adds <linux/elfnote.h>, which defines C and Assembler macros
+for actually creating ELF notes.
+
+Signed-off-by: Jeremy Fitzhardinge <jeremy@xxxxxxxxxxxxx>
+Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
+Cc: Hollis Blanchard <hollisb@xxxxxxxxxx>
+Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
+---
+
+ arch/i386/kernel/vmlinux.lds.S    |   12 +++
+ include/asm-generic/vmlinux.lds.h |    3 
+ include/linux/elfnote.h           |   88 ++++++++++++++++++++++++++++
+ 3 files changed, 101 insertions(+), 2 deletions(-)
+
+diff -puN 
arch/i386/kernel/vmlinux.lds.S~x86-put-note-sections-into-a-pt_note-segment-in-vmlinux
 arch/i386/kernel/vmlinux.lds.S
+--- 
a/arch/i386/kernel/vmlinux.lds.S~x86-put-note-sections-into-a-pt_note-segment-in-vmlinux
++++ a/arch/i386/kernel/vmlinux.lds.S
+@@ -13,6 +13,12 @@ OUTPUT_FORMAT("elf32-i386", "elf32-i386"
+ OUTPUT_ARCH(i386)
+ ENTRY(phys_startup_32)
+ jiffies = jiffies_64;
++
++PHDRS {
++      text PT_LOAD FLAGS(5);  /* R_E */
++      data PT_LOAD FLAGS(7);  /* RWE */
++      note PT_NOTE FLAGS(4);  /* R__ */
++}
+ SECTIONS
+ {
+   . = __KERNEL_START;
+@@ -26,7 +32,7 @@ SECTIONS
+       KPROBES_TEXT
+       *(.fixup)
+       *(.gnu.warning)
+-      } = 0x9090
++      } :text = 0x9090
+ 
+   _etext = .;                 /* End of text section */
+ 
+@@ -50,7 +56,7 @@ SECTIONS
+   .data : AT(ADDR(.data) - LOAD_OFFSET) {     /* Data */
+       *(.data)
+       CONSTRUCTORS
+-      }
++      } :data
+ 
+   . = ALIGN(4096);
+   __nosave_begin = .;
+@@ -186,4 +192,6 @@ SECTIONS
+   STABS_DEBUG
+ 
+   DWARF_DEBUG
++
++  NOTES
+ }
+diff -puN 
include/asm-generic/vmlinux.lds.h~x86-put-note-sections-into-a-pt_note-segment-in-vmlinux
 include/asm-generic/vmlinux.lds.h
+--- 
a/include/asm-generic/vmlinux.lds.h~x86-put-note-sections-into-a-pt_note-segment-in-vmlinux
++++ a/include/asm-generic/vmlinux.lds.h
+@@ -194,3 +194,6 @@
+               .stab.index 0 : { *(.stab.index) }                      \
+               .stab.indexstr 0 : { *(.stab.indexstr) }                \
+               .comment 0 : { *(.comment) }
++
++#define NOTES                                                         \
++              .notes : { *(.note.*) } :note
+diff -puN /dev/null include/linux/elfnote.h
+--- /dev/null
++++ a/include/linux/elfnote.h
+@@ -0,0 +1,88 @@
++#ifndef _LINUX_ELFNOTE_H
++#define _LINUX_ELFNOTE_H
++/*
++ * Helper macros to generate ELF Note structures, which are put into a
++ * PT_NOTE segment of the final vmlinux image.  These are useful for
++ * including name-value pairs of metadata into the kernel binary (or
++ * modules?) for use by external programs.
++ *
++ * Each note has three parts: a name, a type and a desc.  The name is
++ * intended to distinguish the note's originator, so it would be a
++ * company, project, subsystem, etc; it must be in a suitable form for
++ * use in a section name.  The type is an integer which is used to tag
++ * the data, and is considered to be within the "name" namespace (so
++ * "FooCo"'s type 42 is distinct from "BarProj"'s type 42).  The
++ * "desc" field is the actual data.  There are no constraints on the
++ * desc field's contents, though typically they're fairly small.
++ *
++ * All notes from a given NAME are put into a section named
++ * .note.NAME.  When the kernel image is finally linked, all the notes
++ * are packed into a single .notes section, which is mapped into the
++ * PT_NOTE segment.  Because notes for a given name are grouped into
++ * the same section, they'll all be adjacent the output file.
++ *
++ * This file defines macros for both C and assembler use.  Their
++ * syntax is slightly different, but they're semantically similar.
++ *
++ * See the ELF specification for more detail about ELF notes.
++ */
++
++#ifdef __ASSEMBLER__
++/*
++ * Generate a structure with the same shape as Elf{32,64}_Nhdr (which
++ * turn out to be the same size and shape), followed by the name and
++ * desc data with appropriate padding.  The 'desc' argument includes
++ * the assembler pseudo op defining the type of the data: .asciz
++ * "hello, world"
++ */
++.macro ELFNOTE name type desc:vararg
++.pushsection ".note.\name"
++  .align 4
++  .long 2f - 1f                       /* namesz */
++  .long 4f - 3f                       /* descsz */
++  .long \type
++1:.asciz "\name"
++2:.align 4
++3:\desc
++4:.align 4
++.popsection
++.endm
++#else /* !__ASSEMBLER__ */
++#include <linux/elf.h>
++/*
++ * Use an anonymous structure which matches the shape of
++ * Elf{32,64}_Nhdr, but includes the name and desc data.  The size and
++ * type of name and desc depend on the macro arguments.  "name" must
++ * be a literal string, and "desc" must be passed by value.  You may
++ * only define one note per line, since __LINE__ is used to generate
++ * unique symbols.
++ */
++#define _ELFNOTE_PASTE(a,b)   a##b
++#define _ELFNOTE(size, name, unique, type, desc)                      \
++      static const struct {                                           \
++              struct elf##size##_note _nhdr;                          \
++              unsigned char _name[sizeof(name)]                       \
++              __attribute__((aligned(sizeof(Elf##size##_Word))));     \
++              typeof(desc) _desc                                      \
++                           
__attribute__((aligned(sizeof(Elf##size##_Word)))); \
++      } _ELFNOTE_PASTE(_note_, unique)                                \
++              __attribute_used__                                      \
++              __attribute__((section(".note." name),                  \
++                             aligned(sizeof(Elf##size##_Word)),       \
++                             unused)) = {                             \
++              {                                                       \
++                      sizeof(name),                                   \
++                      sizeof(desc),                                   \
++                      type,                                           \
++              },                                                      \
++              name,                                                   \
++              desc                                                    \
++      }
++#define ELFNOTE(size, name, type, desc)               \
++      _ELFNOTE(size, name, __LINE__, type, desc)
++
++#define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc)
++#define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc)
++#endif        /* __ASSEMBLER__ */
++
++#endif /* _LINUX_ELFNOTE_H */
+_
diff -r cd4e7ace4e58 -r a4550b748840 
patches/linux-2.6.16.13/x86_64-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ 
b/patches/linux-2.6.16.13/x86_64-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch
  Tue Aug 22 12:20:43 2006 +0100
@@ -0,0 +1,40 @@
+diff -urN ref-linux-2.6.16.13/arch/x86_64/kernel/vmlinux.lds.S 
x86-64_elfnotes/arch/x86_64/kernel/vmlinux.lds.S
+--- ref-linux-2.6.16.13/arch/x86_64/kernel/vmlinux.lds.S       2006-05-02 
22:38:44.000000000 +0100
++++ x86-64_elfnotes/arch/x86_64/kernel/vmlinux.lds.S   2006-08-22 
11:39:14.000000000 +0100
+@@ -14,6 +14,11 @@
+ OUTPUT_ARCH(i386:x86-64)
+ ENTRY(phys_startup_64)
+ jiffies_64 = jiffies;
++PHDRS {
++      text PT_LOAD FLAGS(5);  /* R_E */
++      data PT_LOAD FLAGS(7);  /* RWE */
++      note PT_NOTE FLAGS(4);  /* R__ */
++}
+ SECTIONS
+ {
+   . = __START_KERNEL;
+@@ -26,7 +31,7 @@
+       KPROBES_TEXT
+       *(.fixup)
+       *(.gnu.warning)
+-      } = 0x9090
++      } :text = 0x9090
+                               /* out-of-line lock text */
+   .text.lock : AT(ADDR(.text.lock) - LOAD_OFFSET) { *(.text.lock) }
+ 
+@@ -43,7 +48,7 @@
+   .data : AT(ADDR(.data) - LOAD_OFFSET) {
+       *(.data)
+       CONSTRUCTORS
+-      }
++      } :data
+ 
+   _edata = .;                 /* End of data section */
+ 
+@@ -201,4 +206,6 @@
+   STABS_DEBUG
+ 
+   DWARF_DEBUG
++
++  NOTES
+ }

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