[RFC,v5,3/6] Document -z unique/-z nounique in the ld man page and help output

Message ID 79148d7b21efab6e1763bf44d271015fd86623fe.1594396647.git.vivek@collabora.com
State Superseded
Headers show
  • binutils patches for DT_GNU_FLAGS_1/DF_GNU_1_UNIQUE
Related show

Commit Message

H.J. Lu via Binutils July 10, 2020, 4:01 p.m.
 ld/ChangeLog |  2 ++
 ld/ld.texi   | 10 ++++++++++
 ld/lexsup.c  |  4 ++++
 3 files changed, 16 insertions(+)



diff --git a/ld/ChangeLog b/ld/ChangeLog
index b10c354776..45fa71f6cf 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -2,6 +2,8 @@ 
 	* emultempl/elf.em (gld${EMULATION_NAME}_handle_option):
 	Parse -z unique / -z nounique options.
+	* ld.texi (Options): Document -z unique and -z nounique.
+	* lexsup.c (elf_shlib_list_options): Likewise.
 2020-07-10  Alan Modra  <amodra@gmail.com>
diff --git a/ld/ld.texi b/ld/ld.texi
index 165a3d935e..61bf4e0fa9 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -1305,6 +1305,16 @@  Specify that the dynamic loader should modify its symbol search order
 so that symbols in this shared library interpose all other shared
 libraries not so marked.
+@item unique
+@itemx nounique
+When generating a shared library or other dynamically loadable ELF
+object mark it as one that should (by default) only ever be loaded once,
+and only in the main namespace (when using @code{dlmopen}). This is
+primarily used to mark fundamental libraries such as libc, libpthread et
+al which do not usually function correctly unless they are the sole instances
+of themselves. This behaviour can be overridden by the @code{dlmopen} caller
+and does not apply to certain loading mechanisms (such as audit libraries).
 @item lazy
 When generating an executable or shared library, mark it to tell the
 dynamic linker to defer function call resolution to the point when
diff --git a/ld/lexsup.c b/ld/lexsup.c
index a79bec0b45..1f12ccb4c0 100644
--- a/ld/lexsup.c
+++ b/ld/lexsup.c
@@ -1925,6 +1925,10 @@  elf_shlib_list_options (FILE *file)
   fprintf (file, _("\
   -z interpose                Mark object to interpose all DSOs but executable\n"));
   fprintf (file, _("\
+  -z unique                   Mark DSO to be loaded at most once by default, and only in the main namespace\n"));
+  fprintf (file, _("\
+  -z nounique                 Don't mark DSO as a loadable at most once\n"));
+  fprintf (file, _("\
   -z lazy                     Mark object lazy runtime binding (default)\n"));
   fprintf (file, _("\
   -z loadfltr                 Mark object requiring immediate process\n"));