Fix issue NixOS#66 by ignoring the first section header when sorting, and not overwriting NOBITS entries.

Author: ezquat

src/patchelf.cc

@@ -475,7 +475,7 @@ void ElfFile<ElfFileParamNames>::sortShdrs()
     /* Sort the sections by offset. */
     CompShdr comp;
     comp.elfFile = this;
-    sort(shdrs.begin(), shdrs.end(), comp);
+    sort(shdrs.begin() + 1, shdrs.end(), comp);
 
     /* Restore the sh_link mappings. */
     for (unsigned int i = 1; i < rdi(hdr->e_shnum); ++i)
@@ -642,7 +642,8 @@ void ElfFile<ElfFileParamNames>::writeReplacedSections(Elf_Off & curOff,
     for (auto & i : replacedSections) {
         std::string sectionName = i.first;
         Elf_Shdr & shdr = findSection(sectionName);
-        memset(contents + rdi(shdr.sh_offset), 'X', rdi(shdr.sh_size));
+        if (shdr.sh_type != SHT_NOBITS)
+            memset(contents + rdi(shdr.sh_offset), 'X', rdi(shdr.sh_size));
     }
 
     for (auto & i : replacedSections) {