Merge pull request #2 from cmatsuoka/0.9+snapcraft

Local patches for patchelf 0.9

src/Makefile.am

@@ -1,4 +1,4 @@
-AM_CXXFLAGS = -Wall
+AM_CXXFLAGS = -Wall -std=c++11
 
 bin_PROGRAMS = patchelf
 

src/patchelf.cc

@@ -146,6 +146,8 @@ class ElfFile
     string & replaceSection(const SectionName & sectionName,
         unsigned int size);
 
+    bool haveReplacedSection(const SectionName & sectionName);
+
     void writeReplacedSections(Elf_Off & curOff,
         Elf_Addr startAddr, Elf_Off startOffset);
 
@@ -366,7 +368,7 @@ 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)
@@ -483,6 +485,15 @@ unsigned int ElfFile<ElfFileParamNames>::findSection3(const SectionName & sectio
     return 0;
 }
 
+template<ElfFileParams>
+bool ElfFile<ElfFileParamNames>::haveReplacedSection(const SectionName & sectionName)
+{
+    ReplacedSections::iterator i = replacedSections.find(sectionName);
+
+    if (i != replacedSections.end())
+        return true;
+    return false;
+}
 
 template<ElfFileParams>
 string & ElfFile<ElfFileParamNames>::replaceSection(const SectionName & sectionName,
@@ -517,7 +528,8 @@ void ElfFile<ElfFileParamNames>::writeReplacedSections(Elf_Off & curOff,
     {
         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 (ReplacedSections::iterator i = replacedSections.begin();
@@ -581,52 +593,49 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
 
     debug("last page is 0x%llx\n", (unsigned long long) startPage);
 
+    /* Because we're adding a new section header, we're necessarily increasing
+       the size of the program header table.  This can cause the first section
+       to overlap the program header table in memory; we need to shift the first
+       few segments to someplace else. */
+    /* Some sections may already be replaced so account for that */
+    unsigned int i = 1;
+    Elf_Addr pht_size = sizeof(Elf_Ehdr) + (phdrs.size() + 1)*sizeof(Elf_Phdr);
+    while( shdrs[i].sh_addr <= pht_size && i < rdi(hdr->e_shnum) ) {
+        if (not haveReplacedSection(getSectionName(shdrs[i])))
+            replaceSection(getSectionName(shdrs[i]), shdrs[i].sh_size);
+        i++;
+    }
 
-    /* Compute the total space needed for the replaced sections and
-       the program headers. */
-    off_t neededSpace = (phdrs.size() + 1) * sizeof(Elf_Phdr);
-    for (ReplacedSections::iterator i = replacedSections.begin();
-         i != replacedSections.end(); ++i)
-        neededSpace += roundUp(i->second.size(), sectionAlignment);
+    /* Compute the total space needed for the replaced sections */
+    off_t neededSpace = 0;
+    for (auto & i : replacedSections)
+        neededSpace += roundUp(i.second.size(), sectionAlignment);
     debug("needed space is %d\n", neededSpace);
 
-
     size_t startOffset = roundUp(fileSize, getPageSize());
 
     growFile(startOffset + neededSpace);
 
-
     /* Even though this file is of type ET_DYN, it could actually be
        an executable.  For instance, Gold produces executables marked
-       ET_DYN.  In that case we can still hit the kernel bug that
-       necessitated rewriteSectionsExecutable().  However, such
-       executables also tend to start at virtual address 0, so
+       ET_DYN as does LD when linking with pie. If we move PT_PHDR, it
+       has to stay in the first PT_LOAD segment or any subsequent ones
+       if they're continuous in memory due to linux kernel constraints
+       (see BUGS). Since the end of the file would be after bss, we can't 
+       move PHDR there, we therefore choose to leave PT_PHDR where it is but
+       move enough following sections such that we can add the extra PT_LOAD
+       section to it. This PT_LOAD segment ensures the sections at the end of
+       the file are mapped into memory for ld.so to process.
+       We can't use the approach in rewriteSectionsExecutable()
+       since DYN executables tend to start at virtual address 0, so
        rewriteSectionsExecutable() won't work because it doesn't have
-       any virtual address space to grow downwards into.  As a
-       workaround, make sure that the virtual address of our new
-       PT_LOAD segment relative to the first PT_LOAD segment is equal
-       to its offset; otherwise we hit the kernel bug.  This may
-       require creating a hole in the executable.  The bigger the size
-       of the uninitialised data segment, the bigger the hole. */
-    if (isExecutable) {
-        if (startOffset >= startPage) {
-            debug("shifting new PT_LOAD segment by %d bytes to work around a Linux kernel bug\n", startOffset - startPage);
-        } else {
-            size_t hole = startPage - startOffset;
-            /* Print a warning, because the hole could be very big. */
-            fprintf(stderr, "warning: working around a Linux kernel bug by creating a hole of %zu bytes in ‘%s’\n", hole, fileName.c_str());
-            assert(hole % getPageSize() == 0);
-            /* !!! We could create an actual hole in the file here,
-               but it's probably not worth the effort. */
-            growFile(fileSize + hole);
-            startOffset += hole;
-        }
+       any virtual address space to grow downwards into. */
+    if (isExecutable && startOffset > startPage) {
+        debug("shifting new PT_LOAD segment by %d bytes to work around a Linux kernel bug\n", startOffset - startPage);
         startPage = startOffset;
     }
 
-
-    /* Add a segment that maps the replaced sections and program
-       headers into memory. */
+    /* Add a segment that maps the replaced sections into memory. */
     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];
@@ -639,15 +648,12 @@ void ElfFile<ElfFileParamNames>::rewriteSectionsLibrary()
 
 
     /* Write out the replaced sections. */
-    Elf_Off curOff = startOffset + phdrs.size() * sizeof(Elf_Phdr);
+    Elf_Off curOff = startOffset;
     writeReplacedSections(curOff, startPage, startOffset);
     assert(curOff == startOffset + neededSpace);
 
-
-    /* Move the program header to the start of the new area. */
-    wri(hdr->e_phoff, startOffset);
-
-    rewriteHeaders(startPage);
+    /* Write out the updated program and section headers */
+    rewriteHeaders(hdr->e_phoff);
 }
 
 

tests/no-rpath-prebuild.sh

@@ -1,6 +1,7 @@
 #! /bin/sh -e
 set -x
 ARCH="$1"
+PAGESIZE=4096
 
 if [ -z "$ARCH" ]; then
   ARCH=$(basename $0 .sh | sed -e 's/.*-//')
@@ -25,13 +26,13 @@ mkdir -p ${SCRATCH}
 
 cp $no_rpath_bin ${SCRATCH}/no-rpath
 
-oldRPath=$(../src/patchelf --print-rpath ${SCRATCH}/no-rpath)
+oldRPath=$(../src/patchelf --page-size ${PAGESIZE} --print-rpath ${SCRATCH}/no-rpath)
 if test -n "$oldRPath"; then exit 1; fi
-../src/patchelf \
-  --set-interpreter "$(../src/patchelf --print-interpreter ../src/patchelf)" \
+../src/patchelf --page-size ${PAGESIZE} \
+  --set-interpreter "$(../src/patchelf --page-size ${PAGESIZE} --print-interpreter ../src/patchelf)" \
   --set-rpath /foo:/bar:/xxxxxxxxxxxxxxx ${SCRATCH}/no-rpath
 
-newRPath=$(../src/patchelf --print-rpath ${SCRATCH}/no-rpath)
+newRPath=$(../src/patchelf --page-size ${PAGESIZE} --print-rpath ${SCRATCH}/no-rpath)
 if ! echo "$newRPath" | grep -q '/foo:/bar'; then
     echo "incomplete RPATH"
     exit 1