[PATCH] use elfnote.h to generate vsyscall notes

[PATCH] use elfnote.h to generate vsyscall notes

[Jeremy Fitzhardinge]

Use existing elfnote.h to generate vsyscall notes, rather than doing
it locally.  Changes elfnote.h a bit to suite, since this is the first
asm user, and it wasn't quite right.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Roland McGrath <roland@redhat.com>

---
 arch/i386/kernel/vsyscall-note.S |   23 ++++++-----------------
 include/linux/elfnote.h          |   18 +++++++++++++-----
 2 files changed, 19 insertions(+), 22 deletions(-)

===================================================================
--- a/arch/i386/kernel/vsyscall-note.S
+++ b/arch/i386/kernel/vsyscall-note.S
@@ -3,23 +3,12 @@
  * Here we can supply some information useful to userland.
  */
 
-#include <linux/uts.h>
 #include <linux/version.h>
+#include <linux/elfnote.h>
 
-#define ASM_ELF_NOTE_BEGIN(name, flags, vendor, type)			      \
-	.section name, flags;						      \
-	.balign 4;							      \
-	.long 1f - 0f;		/* name length */			      \
-	.long 3f - 2f;		/* data length */			      \
-	.long type;		/* note type */				      \
-0:	.asciz vendor;		/* vendor name */			      \
-1:	.balign 4;							      \
-2:
-
-#define ASM_ELF_NOTE_END						      \
-3:	.balign 4;		/* pad out section */			      \
-	.previous
-
-	ASM_ELF_NOTE_BEGIN(".note.kernel-version", "a", UTS_SYSNAME, 0)
+/* Ideally this would use UTS_NAME, but using a quoted string here
+   doesn't work. Remember to change this when changing the
+   kernel's name. */
+ELFNOTE_START(Linux, 0, "a")
 	.long LINUX_VERSION_CODE
-	ASM_ELF_NOTE_END
+ELFNOTE_END
===================================================================
--- a/include/linux/elfnote.h
+++ b/include/linux/elfnote.h
@@ -38,17 +38,25 @@
  * e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two")
  *      ELFNOTE(XYZCo, 12, .long, 0xdeadbeef)
  */
-#define ELFNOTE(name, type, desctype, descdata)	\
-.pushsection .note.name, "",@note	;	\
+#define ELFNOTE_START(name, type, flags)	\
+.pushsection .note.name, flags,@note	;	\
   .align 4				;	\
   .long 2f - 1f		/* namesz */	;	\
-  .long 4f - 3f		/* descsz */	;	\
+  .long 4484f - 3f	/* descsz */	;	\
   .long type				;	\
 1:.asciz #name				;	\
 2:.align 4				;	\
-3:desctype descdata			;	\
-4:.align 4				;	\
+3:
+
+#define ELFNOTE_END				\
+4484:.align 4				;	\
 .popsection				;
+
+#define ELFNOTE(name, type, desc)		\
+	ELFNOTE_START(name, type, "")		\
+		desc			;	\
+	ELFNOTE_END
+
 #else	/* !__ASSEMBLER__ */
 #include <linux/elf.h>
 /*

Re: [PATCH] use elfnote.h to generate vsyscall notes

[Roland McGrath]

Please don't change the section name that way.  I don't see why the macros
should do differently than what was in vsyscall-note.S to begin with.


Thanks,
Roland

Re: [PATCH] use elfnote.h to generate vsyscall notes

[Jeremy Fitzhardinge]

Roland McGrath wrote:
> Please don't change the section name that way. 

Does the section name matter? I've been operating under the assumption
that it doesn't, other that needing to start with .note. Using
.note.vendor means that all the vendor's notes will get grouped
properly, but other than that it seems much of a muchness.

>  I don't see why the macros
> should do differently than what was in vsyscall-note.S to begin with.
>   
Well, passing the section name seems redundant unless its actually
needed. In this case it will go from .note.kernel-version to
.note.Linux, but it will end up being called .note in the final vdso
regardless.

J

Re: [PATCH] use elfnote.h to generate vsyscall notes

[Roland McGrath]

You're right.  I was thinking of the output section name in the DSO.