Fix shared library corruption when rerunning patchelf

When running patchelf on some existing patchelf'd binaries to change to longer
RPATHS, ldd would report the binaries as invalid. The output of objdump -x on
those libraryies should show the top of the .dynamic section is getting trashed,
something like:

0x600000001 0x0000000000429000
0x335000 0x0000000000335000
0xc740 0x000000000000c740
0x1000 0x0000000000009098
SONAME libglib-2.0.so.0

(which should be RPATH and DT_NEEDED entries)

This was tracked down to the code which injects the PT_LOAD section.

The issue is that if the program headers were previously relocated to the end
of the file which was how patchelf operated previously, the relocation code
wouldn't work properly on a second run as it now assumes they're located after
the elf header. This change forces them back to immediately follow the elf
header which is where the code has made space for them.

Should fix #170
and #192

Signed-off-by: Richard Purdie <[email protected]>

Author: rpurdie

src/patchelf.cc

@@ -754,6 +754,7 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
     }
 
     /* Add a segment that maps the replaced sections into memory. */
+    wri(hdr->e_phoff, sizeof(Elf_Ehdr));
     phdrs.resize(rdi(hdr->e_phnum) + 1);
     wri(hdr->e_phnum, rdi(hdr->e_phnum) + 1);
     Elf_Phdr & phdr = phdrs[rdi(hdr->e_phnum) - 1];