On Wed, 2006-08-23 at 10:47 -0700, Jeremy Fitzhardinge wrote:

I remember now why I decided to use the assembler macro rather than 
cpp.  The macro names the section after the note name (".note.NAME"), 
and it needs to be quoted so that the name can have spaces and other 
characters which would otherwise upset the assembler.  I couldn't work
out a clean way to do this with the C preprocessor, since "as" doesn't
support string concatenation like C does. 

Surprisingly string concatenation doesn't appear to be required for the
majority of punctuation, at least so far as I can tell with this test
patch (this is a xen-unstable kernel I had lying around so don't pay too
much attention to head-xen.S bit). The only problem I found is comma,
which can't be escaped.

I've no idea how reliably this works across tool chain versions etc
though. It worked for me ;-)

--- ref-linux-2.6.16.13/include/linux/elfnote.h	2006-08-23 20:08:56.000000000 +0100
+++ linux-2.6.16.13-xen/include/linux/elfnote.h	2006-08-23 20:10:00.000000000 +0100

@@ -39,7 +39,7 @@
  *      ELFNOTE(XYZCo, 12, .long, 0xdeadbeef)
  */
 #define ELFNOTE(name, type, desctype, descdata)	\
-.pushsection .note.name			;	\
+.pushsection ".note.name"		;	\
   .align 4				;	\
   .long 2f - 1f		/* namesz */	;	\
   .long 4f - 3f		/* descsz */	;	\

diff -r 58b5141c8309 linux-2.6-xen-sparse/arch/i386/kernel/head-xen.S

--- a/linux-2.6-xen-sparse/arch/i386/kernel/head-xen.S	Wed Aug 23 14:43:48 2006 +0100
+++ b/linux-2.6-xen-sparse/arch/i386/kernel/head-xen.S	Wed Aug 23 20:27:05 2006 +0100

@@ -199,3 +199,11 @@ ENTRY(cpu_gdt_table)
 	ELFNOTE(Xen, XEN_ELFNOTE_PAE_MODE,       .asciz, "no")
 #endif
 	ELFNOTE(Xen, XEN_ELFNOTE_LOADER,         .asciz, "generic")
+
+	ELFNOTE(XYZ Co., 42, .asciz, "forty-two")
+	ELFNOTE(XYZ Co., 12, .long, 0xdeadbeef)
+	ELFNOTE(!\"£$%^\\&, 12, .long, 0xdeadbeef)
+	ELFNOTE(*\(\)-+-=<, 12, .long, 0xdeadbeef)
+	ELFNOTE(>./?\;\'#:, 12, .long, 0xdeadbeef)
+	ELFNOTE(@~, 12, .long, 0xdeadbeef)
+

$ readelf -S --segments arch/i386/kernel/head-xen.o
...
  [ 7] .note.Xen         NOTE            00000000 002260 000144 00      0   0  4
  [ 8] .rel.note.Xen     REL             00000000 003018 000010 08     15   7  4
  [ 9] .note.XYZ Co.     NOTE            00000000 0023a4 000038 00      0   0  4
  [10] .note.!"£$%^\&   NOTE            00000000 0023dc 00001c 00      0   0  4
  [11] .note.*()-+-=<    NOTE            00000000 0023f8 00001c 00      0   0  4
  [12] .note.>./?;'#:    NOTE            00000000 002414 00001c 00      0   0  4
  [13] .note.@~          NOTE            00000000 002430 000014 00      0   0  4
...

$ objdump -j .notes -s vmlinux
...
 85a8 72696300 08000000 0a000000 2a000000  ric.........*...
 85b8 58595a20 436f2e00 666f7274 792d7477  XYZ Co..forty-tw
 85c8 6f000000 08000000 04000000 0c000000  o...............
 85d8 58595a20 436f2e00 efbeadde 0a000000  XYZ Co..........
 85e8 04000000 0c000000 2122c2a3 24255e5c  ........!"..$%^\
 85f8 26000000 efbeadde 09000000 04000000  &...............
 8608 0c000000 2a28292d 2b2d3d3c 00000000  ....*()-+-=<....
 8618 efbeadde 09000000 04000000 0c000000  ................
 8628 3e2e2f3f 3b27233a 00000000 efbeadde  >./?;'#:........
 8638 03000000 04000000 0c000000 407e0000  ............@~..
 8648 efbeadde                             ....
...