Fix MIPS non-NOBITS after NOBITS in segment error

Fix MIPS non-NOBITS after NOBITS in segment error

[Mark Hatle]

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With recent compilers and linkers it is typical for a MIPS binary to
be built with the sections such as:

       [23] .got              PROGBITS        004aafb0 09afb0 00055c 04 WAp  0  $
       [24] .sdata            PROGBITS        004ab50c 09b50c 000004 00 WAp  0  $
       [25] .sbss             NOBITS          004ab510 09b510 00003d 00 WAp  0  $
       [26] .bss              NOBITS          004ab550 09b510 0021cc 00  WA  0  $
       [27] .dynstr           STRTAB          004bb510 09b510 000b99 00   A  0  $
       [28] .gnu.attributes   LOOS+ffffff5    00000000 09c0a9 000010 00      0  $
       [29] .mdebug.abi32     PROGBITS        004ad71c 09c0b9 000000 00      0  $
       [30] .gnu_debuglink    PROGBITS        00000000 09c0b9 00000c 00      0  $
       [31] .gnu.prelink_undo PROGBITS        00000000 09c0c8 0005bc 01      0  $

When determining if a section is within a segment, simply checking
that it fits within the boundaries of that segment is not enough.  In
the above example, the .mdebug.abi32 fits within the boundaries of the
third segment.  However with a size of 0 there is nothing for the
prelinker to do.  The validation that non-NOBITS sections can't come
after a PROGBITS fails, because it incorrectly assumes that it is
part of the same section as .sbss, and .bss.

Using elfutils readelf as a guide, a check was missing in the mapping
function that the section had a size > 0.  Binutils has a similar
check, but it is a bit more specific that the address of a section
can not start at the end of a segment.  The size > 0 was an easier
and more obvious check, which is why it was used.

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2012-01-04  Mark Hatle <mark.hatle@windriver.com>
        * exec.c: Check that a section is larger then 0 bytes when
          determining the section to segment mapping.  This matches
          the behavior of elfutils - readelf.  Otherwise an empty
          PROGBITS section at the end of a segment will cause a
          failure.

diff --git a/trunk/src/exec.c b/trunk/src/exec.c
index 7c8f38f..cf38b72 100644
--- a/trunk/src/exec.c
+++ b/trunk/src/exec.c
@@ -500,7 +500,8 @@ error_out:
 	int sfirst = 0, slast = 0, last = 0;
 
 	for (j = 1; j < dso->ehdr.e_shnum; ++j)
-	  if (dso->shdr[j].sh_addr >= dso->phdr[i].p_vaddr
+	  if (dso->shdr[j].sh_size > 0
+	      && dso->shdr[j].sh_addr >= dso->phdr[i].p_vaddr
 	      && dso->shdr[j].sh_addr + dso->shdr[j].sh_size
 		 <= dso->phdr[i].p_vaddr + dso->phdr[i].p_memsz)
 	    {
@@ -572,7 +573,8 @@ error_out:
 	  }
 
 	for (j = 1; j < dso->ehdr.e_shnum; ++j)
-	  if (dso->shdr[j].sh_addr >= dso->phdr[i].p_vaddr
+	  if (dso->shdr[j].sh_size > 0
+	      && dso->shdr[j].sh_addr >= dso->phdr[i].p_vaddr
 	      && dso->shdr[j].sh_addr + dso->shdr[j].sh_size
 		 <= dso->phdr[i].p_vaddr + dso->phdr[i].p_memsz)
 	    {