This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / include / linux / elfnote.h

diff --git a/include/linux/elfnote.h b/include/linux/elfnote.h
new file mode 100644 (file)
index 0000000..67396db
--- /dev/null
+++ b/include/linux/elfnote.h
@@ -0,0 +1,90 @@
+#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 */