Apply a workaround for a binutils issue with the .note.ABI-tag section

generated from lib/csu/common/crtbrand.c (which ultimately ends up in
executables and shared libraries, via crt1.o, gcrt1.o or Scrt1.o).

For all arches except sparc, gcc emits the section directive for the
abitag struct in crtbrand.c with a PROGBITS type.  However, newer
versions of binutils (after 2.16.90) require the section to be of NOTE
type, to guarantee that the .note.ABI-tag section correctly ends up in
the first page of the final executable.

Unfortunately, there is no clean way to tell gcc to use another section
type, so crtbrand.c (or the C files that include it) must be compiled in
multiple steps:

- Compile the .c file to a .s file.
- Edit the .s file to change the 'progbits' type to 'note', for the section
  directive that defines the .note.ABI-tag section.
- Compile the .s file to an object file.

These steps are done in the invididual Makefiles for each applicable arch.

Reviewed by:	kib

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/csu/common/crtbrand.c b/lib/csu/common/crtbrand.c
index 684a48e..444d7f1 100644
--- a/lib/csu/common/crtbrand.c
+++ b/lib/csu/common/crtbrand.c
@@ -36,6 +36,23 @@ __FBSDID("$FreeBSD$");
  * Special ".note" entry specifying the ABI version.  See
  * http://www.netbsd.org/Documentation/kernel/elf-notes.html
  * for more information.
+ *
+ * For all arches except sparc, gcc emits the section directive for the
+ * following struct with a PROGBITS type.  However, newer versions of binutils
+ * (after 2.16.90) require the section to be of NOTE type, to guarantee that the
+ * .note.ABI-tag section correctly ends up in the first page of the final
+ * executable.
+ *
+ * Unfortunately, there is no clean way to tell gcc to use another section type,
+ * so this C file (or the C file that includes it) must be compiled in multiple
+ * steps:
+ *
+ * - Compile the .c file to a .s file.
+ * - Edit the .s file to change the 'progbits' type to 'note', for the section
+ *   directive that defines the .note.ABI-tag section.
+ * - Compile the .s file to an object file.
+ *
+ * These steps are done in the invididual Makefiles for each applicable arch.
  */
 static const struct {
     int32_t	namesz;