* config/obj-elf.c (obj_elf_type): Add code to support a type of

        gnu_unique_object.
        * doc/as.texinfo: Document new feature of .type directive.
        * NEWS: Mention support for gnu_unique_object symbol type.

        * common.h (STB_GNU_UNIQUE): Define.

        * NEWS: Mention the linker's support for symbols with a binding of
        STB_GNU_UNIQUE.

        * gas/elf/type.s: Add unique global symbol definition.
        * gas/elf/type.e: Add expected readelf output for global unique
        symbol.

        * elfcpp.h (enum STB): Add STB_GNU_UNIQUE.

        * readelf.c (get_symbol_binding): For Linux targeted files return
        UNIQUE for symbols with the STB_GNU_UNIQUE binding.
        * doc/binutils.texi: Document the meaning of the 'u' symbol
        binding in the output of nm and objdump --syms.

        * elf-bfd.h (struct elf_link_hash_entry): Add unique_global field.
        * elf.c (swap_out_syms): Set binding to STB_GNU_UNIQUE for symbols
        with the BSF_GNU_UNIQUE flag bit set.
        * elfcode.h (elf_slurp_symbol_table): Set the BSF_GNU_UNIQUE flag
        for symbols with STB_GNU_UNIQUE binding.
        * elflink.c (_bfd_elf_merge_symbol): Set unique_global for symbols
        with the STB_GNU_UNIQUE binding.
        (elf_link_add_object_symbols): Set the BSF_GNU_UNIQUE flag for
        symbols with STB_GNU_UNIQUE binding.  Set STB_GNU_UNIQUE for
        symbols with the unique_global field set.
        (elf_link_output_extsym): Set unique_global field for symbols with
        the STB_GNU_UNIQUE binding.
        * syms.c (struct bfd_symbol): Define BSF_GNU_UNIQUE flag bit.
        (bfd_print_symbol_vandf): Print a 'u' character for BSF_GNU_UNIQUE
        symbols.
        (bfd_decode_symclass): Return a 'u' character for BSF_GNU_UNIQUE
        symbols.
        * bfd-in2.h: Regenerate.

1 files changed, 20 insertions, 3 deletions

diff --git a/binutils/doc/binutils.texi b/binutils/doc/binutils.texi
index 98438f2..a5856b2 100644
--- a/binutils/doc/binutils.texi
+++ b/binutils/doc/binutils.texi
@@ -745,7 +745,13 @@ object file formats permit more efficient access to small data objects,
 such as a global int variable as opposed to a large global array.
 
 @item i
-The symbol is in a section specific to the implementation of DLLs.
+For PE format files this indicates that the symbol is in a section
+specific to the implementation of DLLs.  For ELF format files this
+indicates that the symbol is an indirect function.  This is a GNU
+extension to the standard set of ELF symbol types.  It indicates a
+symbol which if referenced by a relocation does not evaluate to its
+address, but instead must be invoked at runtime.  The runtime
+execution will then return the value to be used in the relocation.
 
 @item N
 The symbol is a debugging symbol.
@@ -768,6 +774,12 @@ The symbol is in the text (code) section.
 @item U
 The symbol is undefined.
 
+@item u
+The symbol is a unique global symbol.  This is a GNU extension to the
+standard set of ELF symbol bindings.  For such a symbol the dynamic linker
+will make sure that in the entire process there is just one symbol with
+this name and type in use.
+
 @item V
 @itemx v
 The symbol is a weak object.  When a weak defined symbol is linked with
@@ -2142,11 +2154,16 @@ The flag characters are divided into 7 groups as follows:
 @table @code
 @item l
 @itemx g
+@itemx u
 @itemx !
-The symbol is local (l), global (g), neither (a space) or both (!).  A
+The symbol is a local (l), global (g), unique global (u), neither
+global nor local (a space) or both global and local (!).  A
 symbol can be neither local or global for a variety of reasons, e.g.,
 because it is used for debugging, but it is probably an indication of
-a bug if it is ever both local and global.
+a bug if it is ever both local and global.  Unique global symbols are
+a GNU extension to the standard set of ELF symbol bindings.  For such
+a symbol the dynamic linker will make sure that in the entire process
+there is just one symbol with this name and type in use.
 
 @item w
 The symbol is weak (w) or strong (a space).