[PATCH] readelf: dump the value contained in offset on Rel relocs when -AW are passed

[Andrea Monaco]

  > Also, this looks like it might be a suitable project for someone
  > interested in learning about the binutils.  So I am hoping that you,
  > or someone else will volunteer to have a go ... :-)


Here is the suggested patch.  It will print the value at offset on Rel
relocs; for simplicity, it only does it on 32-bit files, because that's
what I need, but I can easily extend it; also, 64-bit ELFs tend to use
Rela relocs where this feature does not make sense.

The additional column is displayed when -A (--arch-specific) is passed,
as suggested, together with -W for wide mode (I can remove this last
requirement).

There's an ad-hoc flag called show_value_at_off, so we can bind it to
different command line options if needed.

The patch seems to work correctly for me, but feedback is much
appreciated.  Test with "readelf -rAW".


Andrea Monaco



diff --git a/binutils/readelf.c b/binutils/readelf.c
index b45683cd571..92830174c27 100644
--- a/binutils/readelf.c
+++ b/binutils/readelf.c
@@ -235,6 +235,7 @@ static bool do_notes = false;
 static bool do_archive_index = false;
 static bool check_all = false;
 static bool is_32bit_elf = false;
+static bool show_value_at_off = false;  /* On REL relocations, show the value 
at offset */
 static bool decompress_dumps = false;
 static bool do_not_show_symbol_truncation = false;
 static bool do_demangle = false;       /* Pretty print C++ symbol names.  */
@@ -1531,10 +1532,12 @@ dump_relocations (Filedata *          filedata,
        }
       else
        {
-         if (do_wide)
-           printf (_(" Offset     Info    Type                Sym. Value  
Symbol's Name\n"));
+         if (do_wide && show_value_at_off)
+           printf (_(" Offset    Value     Info     Type                Sym. 
Value  Symbol's Name\n"));
+         else if (do_wide)
+           printf (_(" Offset    Info      Type                Sym. Value  
Symbol's Name\n"));
          else
-           printf (_(" Offset     Info    Type            Sym.Value  Sym. 
Name\n"));
+           printf (_(" Offset    Info      Type           Sym. Value  Sym. 
Name\n"));
        }
     }
   else
@@ -1559,6 +1562,8 @@ dump_relocations (Filedata *          filedata,
     {
       const char * rtype;
       bfd_vma offset;
+      bfd_vma file_offset;
+      bfd_vma value;
       bfd_vma inf;
       bfd_vma symtab_index;
       bfd_vma type;
@@ -1571,9 +1576,32 @@ dump_relocations (Filedata *          filedata,
 
       if (is_32bit_elf)
        {
-         printf ("%8.8lx  %8.8lx ",
-                 (unsigned long) offset & 0xffffffff,
-                 (unsigned long) inf & 0xffffffff);
+         if (show_value_at_off && do_wide && rel_type == reltype_rel)
+           {
+             /* offset is an address in memory after loading, now we convert 
to an offset in the file */
+
+             Elf_Internal_Shdr *sec = find_section_by_address (filedata, 
offset);
+             value = 0;
+
+             if (sec)
+               {
+                 file_offset = offset - sec->sh_addr + sec->sh_offset;
+
+                 /* Now read value, or set to zero on failure */
+                 if (!fseek (filedata->handle, file_offset, SEEK_SET))
+                   if (fread (&value, sizeof (value), 1, filedata->handle) != 
1)
+                     value = 0;
+               }
+
+             printf ("%8.8lx  %8.8lx  %8.8lx ",
+                     (unsigned long) offset & 0xffffffff,
+                     (unsigned long) value & 0xffffffff,
+                     (unsigned long) inf & 0xffffffff);
+           }
+         else
+           printf ("%8.8lx  %8.8lx ",
+                   (unsigned long) offset & 0xffffffff,
+                   (unsigned long) inf & 0xffffffff);
        }
       else
        {
@@ -5292,6 +5320,7 @@ parse_args (struct dump_data *dumpdata, int argc, char ** 
argv)
          break;
        case 'A':
          do_arch = true;
+         show_value_at_off = true;
          break;
        case 'D':
          do_using_dynamic = true;