Merge pull request #216 from delroth/pagesize

Improve the default section alignment choice (> 4K page size compat)

2 files changed, 37 insertions, 23 deletions

diff --git a/configure.ac b/configure.ac
index 80f82d7..3af271f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7,24 +7,17 @@ AM_INIT_AUTOMAKE([1.11.1 -Wall -Werror dist-bzip2 foreign color-tests parallel-t
 AM_PROG_CC_C_O
 AC_PROG_CXX
 
-PAGESIZE=auto
+DEFAULT_PAGESIZE=auto
 AC_ARG_WITH([page-size],
    AS_HELP_STRING([--with-page-size=SIZE], [Specify default pagesize (default auto)]),
-   PAGESIZE=$withval
+   DEFAULT_PAGESIZE=$withval
 )
 
-if test "$PAGESIZE" = auto; then
-    if command -v getconf >/dev/null; then
-        PAGESIZE=$(getconf PAGESIZE || getconf PAGE_SIZE)
-    fi
-    if test "$PAGESIZE" = auto -o -z "$PAGESIZE"; then
-        PAGESIZE=4096
-    fi
+if test "$DEFAULT_PAGESIZE" != auto; then
+    AC_DEFINE_UNQUOTED(DEFAULT_PAGESIZE, ${DEFAULT_PAGESIZE})
+    AC_MSG_RESULT([Setting page size to ${DEFAULT_PAGESIZE}])
 fi
 
-AC_DEFINE_UNQUOTED(PAGESIZE, ${PAGESIZE})
-AC_MSG_RESULT([Setting page size to ${PAGESIZE}])
-
 AC_ARG_WITH([asan],
    AS_HELP_STRING([--with-asan], [Link with libasan])
 )
diff --git a/src/patchelf.cc b/src/patchelf.cc
index 2d9077c..ea6c6c0 100644
--- a/src/patchelf.cc
+++ b/src/patchelf.cc
@@ -48,7 +48,11 @@ static bool forceRPath = false;
 static std::vector<std::string> fileNames;
 static std::string outputFileName;
 static bool alwaysWrite = false;
-static int pageSize = PAGESIZE;
+#ifdef DEFAULT_PAGESIZE
+static int forcedPageSize = DEFAULT_PAGESIZE;
+#else
+static int forcedPageSize = -1;
+#endif
 
 typedef std::shared_ptr<std::vector<unsigned char>> FileContents;
 
@@ -81,12 +85,6 @@ static bool hasAllowedPrefix(const std::string & s, const std::vector<std::strin
 }
 
 
-static unsigned int getPageSize()
-{
-    return pageSize;
-}
-
-
 template<ElfFileParams>
 class ElfFile
 {
@@ -161,6 +159,8 @@ private:
 
     friend struct CompShdr;
 
+    unsigned int getPageSize() const;
+
     void sortShdrs();
 
     void shiftFile(unsigned int extraPages, Elf_Addr startPage);
@@ -444,6 +444,29 @@ ElfFile<ElfFileParamNames>::ElfFile(FileContents fileContents)
 
 
 template<ElfFileParams>
+unsigned int ElfFile<ElfFileParamNames>::getPageSize() const
+{
+    if (forcedPageSize > 0)
+        return forcedPageSize;
+
+    // Architectures (and ABIs) can have different minimum section alignment
+    // requirements. There is no authoritative list of these values. The
+    // current list is extracted from GNU gold's source code (abi_pagesize).
+    switch (hdr->e_machine) {
+      case EM_SPARC:
+      case EM_MIPS:
+      case EM_PPC:
+      case EM_PPC64:
+      case EM_AARCH64:
+      case EM_TILEGX:
+        return 0x10000;
+      default:
+        return 0x1000;
+    }
+}
+
+
+template<ElfFileParams>
 void ElfFile<ElfFileParamNames>::sortPhdrs()
 {
     /* Sort the segments by offset. */
@@ -1608,8 +1631,6 @@ static void patchElf()
         if (!printInterpreter && !printRPath && !printSoname && !printNeeded)
             debug("patching ELF file '%s'\n", fileName.c_str());
 
-        debug("Kernel page size is %u bytes\n", getPageSize());
-
         auto fileContents = readFile(fileName);
         std::string outputFileName2 = outputFileName.empty() ? fileName : outputFileName;
 
@@ -1665,8 +1686,8 @@ int mainWrapped(int argc, char * * argv)
         }
         else if (arg == "--page-size") {
             if (++i == argc) error("missing argument");
-            pageSize = atoi(argv[i]);
-            if (pageSize <= 0) error("invalid argument to --page-size");
+            forcedPageSize = atoi(argv[i]);
+            if (forcedPageSize <= 0) error("invalid argument to --page-size");
         }
         else if (arg == "--print-interpreter") {
             printInterpreter = true;