5091e74684
I've come across some problems with the assembly version of the ELFNOTE macro currently in -mm. (in x86-put-note-sections-into-a-pt_note-segment-in-vmlinux.patch) The first is that older gas does not support :varargs in .macro definitions (in my testing 2.17 does while 2.15 does not, I don't know when it became supported). The Changes file says binutils >= 2.12 so I think we need to avoid using it. There are no other uses in mainline or -mm. Old gas appears to just ignore it so you get "too many arguments" type errors. Secondly it seems that passing strings as arguments to assembler macros is broken without varargs. It looks like they get unquoted or each character is treated as a separate argument or something and this causes all manner of grief. I think this is because of the use of -traditional when compiling assembly files. Therefore I have translated the assembler macro into a pre-processor macro. I added the desctype as a separate argument instead of including it with the descdata as the previous version did since -traditional means the ELFNOTE definition after the #else needs to have the same number of arguments (I think so anyway, the -traditional CPP semantics are pretty fscking strange!). With this patch I am able to define elfnotes in assembly like this with both old and new assemblers. ELFNOTE(Xen, XEN_ELFNOTE_GUEST_OS, .asciz, "linux") ELFNOTE(Xen, XEN_ELFNOTE_GUEST_VERSION, .asciz, "2.6") ELFNOTE(Xen, XEN_ELFNOTE_XEN_VERSION, .asciz, "xen-3.0") ELFNOTE(Xen, XEN_ELFNOTE_VIRT_BASE, .long, __PAGE_OFFSET) Which seems reasonable enough. Signed-off-by: Ian Campbell <ian.campbell@xensource.com> Acked-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
91 lines
3.4 KiB
C
91 lines
3.4 KiB
C
#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 'desctype' argument is the
|
|
* assembler pseudo op defining the type of the data e.g. .asciz while
|
|
* 'descdata' is the data itself e.g. "hello, world".
|
|
*
|
|
* e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two")
|
|
* ELFNOTE(XYZCo, 12, .long, 0xdeadbeef)
|
|
*/
|
|
#define ELFNOTE(name, type, desctype, descdata) \
|
|
.pushsection .note.name ; \
|
|
.align 4 ; \
|
|
.long 2f - 1f /* namesz */ ; \
|
|
.long 4f - 3f /* descsz */ ; \
|
|
.long type ; \
|
|
1:.asciz "name" ; \
|
|
2:.align 4 ; \
|
|
3:desctype descdata ; \
|
|
4:.align 4 ; \
|
|
.popsection ;
|
|
#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 */
|