[Bug ld/12641] New: Section symbols get discarded when assigned to the "dot"

[binutils at marino dot st]

http://sourceware.org/bugzilla/show_bug.cgi?id=12641

           Summary: Section symbols get discarded when assigned to the
                    "dot"
           Product: binutils
           Version: 2.22 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ld
        AssignedTo: address@hidden
        ReportedBy: address@hidden


Created attachment 5647
  --> http://sourceware.org/bugzilla/attachment.cgi?id=5647
Dragonfly kernel module used for test case

DragonFly BSD has moved to Binutils 2.21 from 2.17 for its upcoming release. 
During the transition an anomaly was seen, and the cause was traced back to
missing __start_set and __stop_set symbols within a generated file.

It appeared that lang_insert_orphan function was silently discarding the
section label symbols due to being assigned the "dot" (the origin).  It appears
that exp_provide() function used there discards the symbols assigned "." and
exp_assign() function does not.

It has been confirmed that the same problem exists in the head.  Using the
attached file on an i386 platform (confirmed on DragonFly i386 and Ubuntu
i386), and a "stock" binutils built from head:

> /usr/bin222/bin/ld -Bshareable -o test222_stock.ko null.kld
> readelf -s test222_stock.ko | grep __start
> readelf -s test222_stock.ko | grep __stop


I repeated this test using a patched version of binutils (patch follows):
> /usr/bin222/bin/ld -Bshareable -o test222_mod.ko null.kld
> readelf -s test222_mod.ko | grep __start
     7: 000011c0     0 NOTYPE  GLOBAL DEFAULT  ABS __start_set_modmetadata_s
    17: 000011c4     0 NOTYPE  GLOBAL DEFAULT  ABS __start_set_sysuninit_set
    32: 000011b8     0 NOTYPE  GLOBAL DEFAULT  ABS __start_set_sysinit_set
    63: 000011c0     0 NOTYPE  GLOBAL DEFAULT  ABS __start_set_modmetadata_s
    73: 000011c4     0 NOTYPE  GLOBAL DEFAULT  ABS __start_set_sysuninit_set
    88: 000011b8     0 NOTYPE  GLOBAL DEFAULT  ABS __start_set_sysinit_set
> readelf -s test222_mod.ko | grep __stop
    15: 000011c8     0 NOTYPE  GLOBAL DEFAULT  ABS __stop_set_sysuninit_set
    25: 000011c0     0 NOTYPE  GLOBAL DEFAULT  ABS __stop_set_sysinit_set
    54: 000011c4     0 NOTYPE  GLOBAL DEFAULT  ABS __stop_set_modmetadata_se
    71: 000011c8     0 NOTYPE  GLOBAL DEFAULT  ABS __stop_set_sysuninit_set
    81: 000011c0     0 NOTYPE  GLOBAL DEFAULT  ABS __stop_set_sysinit_set
   110: 000011c4     0 NOTYPE  GLOBAL DEFAULT  ABS __stop_set_modmetadata_se


The following patch was used to restore the __start_set and __stop_set sections
that were present in version 2.17 but disappeared by 2.20.  Please confirm that
this is a bug and that the provided patch is the proper fix for the bug.


diff --git a/ld/ldlang.c b/ld/ldlang.c
index 76b02f4..6a6b09e 100644
--- a/ld/ldlang.c
+++ b/ld/ldlang.c
@@ -1821,10 +1821,9 @@ lang_insert_orphan (asection *s,
       e_align = exp_unop (ALIGN_K,
                   exp_intop ((bfd_vma) 1 << s->alignment_power));
       lang_add_assignment (exp_assign (".", e_align));
-      lang_add_assignment (exp_provide (symname,
+      lang_add_assignment (exp_assign (symname,
                         exp_unop (ABSOLUTE,
-                              exp_nameop (NAME, ".")),
-                        FALSE));
+                          exp_nameop (NAME, "."))));
     }
     }

@@ -1854,9 +1853,8 @@ lang_insert_orphan (asection *s,
       symname = (char *) xmalloc (ps - secname + sizeof "__stop_" + 1);
       symname[0] = bfd_get_symbol_leading_char (link_info.output_bfd);
       sprintf (symname + (symname[0] != 0), "__stop_%s", secname);
-      lang_add_assignment (exp_provide (symname,
-                    exp_nameop (NAME, "."),
-                    FALSE));
+      lang_add_assignment (exp_assign (symname,
+                    exp_nameop (NAME, ".")));
     }

   /* Restore the global list pointer.  */

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