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[deliverable/binutils-gdb.git] / bfd / coffcode.h

diff --git a/bfd/coffcode.h b/bfd/coffcode.h
index a198e1c730f6511c1e16cdc1925521115339db80..542b5b7039d92deafaef390a4bf6239a96e3efb6 100644 (file)
--- a/bfd/coffcode.h
+++ b/bfd/coffcode.h
@@ -3363,36 +3363,38 @@ coff_compute_section_file_positions (bfd * abfd)
             padding the previous section up if necessary.  */
          old_sofar = sofar;
 
+         sofar = BFD_ALIGN (sofar, 1 << current->alignment_power);
+
 #ifdef RS6000COFF_C
-         /* AIX loader checks the text section alignment of (vma - filepos)
-            So even though the filepos may be aligned wrt the o_algntext, for
-            AIX executables, this check fails. This shows up when a native
-            AIX executable is stripped with gnu strip because the default vma
-            of native is 0x10000150 but default for gnu is 0x10000140.  Gnu
-            stripped gnu excutable passes this check because the filepos is
-            0x0140.  This problem also show up with 64 bit shared objects. The
-            data section must also be aligned.  */
+         /* Make sure the file offset and the vma of .text/.data are at the
+            same page offset, so that the file can be mmap'ed without being
+            relocated.  Failing that, AIX is able to load and execute the
+            program, but it will be silently relocated (possible as
+            executables are PIE).  But the relocation is slightly costly and
+            complexify the use of addr2line or gdb.  So better to avoid it,
+            like does the native linker.  Usually gnu ld makes sure that
+            the vma of .text is the file offset so this issue shouldn't
+            appear unless you are stripping such an executable.
+
+            AIX loader checks the text section alignment of (vma - filepos),
+            and the native linker doesn't try to align the text sections.
+            For example:
+
+            0 .text         000054cc  10000128  10000128  00000128  2**5
+                             CONTENTS, ALLOC, LOAD, CODE
+         */
+
          if (!strcmp (current->name, _TEXT)
              || !strcmp (current->name, _DATA))
            {
-             bfd_vma pad;
-             bfd_vma align;
-
-             sofar = BFD_ALIGN (sofar, 1 << current->alignment_power);
-
-             align = 1 << current->alignment_power;
-             pad = abs (current->vma - sofar) % align;
-
-             if (pad)
-               {
-                 pad = align - pad;
-                 sofar += pad;
-               }
-           }
-         else
-#else
-           {
-             sofar = BFD_ALIGN (sofar, 1 << current->alignment_power);
+             bfd_vma align = 4096;
+             bfd_vma sofar_off = sofar % align;
+             bfd_vma vma_off = current->vma % align;
+
+             if (vma_off > sofar_off)
+               sofar += vma_off - sofar_off;
+             else if (vma_off < sofar_off)
+               sofar += align + vma_off - sofar_off;
            }
 #endif
          if (previous != NULL)