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Improve the default section alignment choice (> 4K page size compat) #216

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merged 1 commit into from
Jun 23, 2020
Merged

Improve the default section alignment choice (> 4K page size compat) #216

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17 changes: 5 additions & 12 deletions configure.ac
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Original file line number Diff line number Diff line change
Expand Up @@ -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])
)
Expand Down
43 changes: 32 additions & 11 deletions src/patchelf.cc
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Expand Up @@ -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;

Expand Down Expand Up @@ -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
{
Expand Down Expand Up @@ -161,6 +159,8 @@ class ElfFile

friend struct CompShdr;

unsigned int getPageSize() const;

void sortShdrs();

void shiftFile(unsigned int extraPages, Elf_Addr startPage);
Expand Down Expand Up @@ -443,6 +443,29 @@ 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()
{
Expand Down Expand Up @@ -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;

Expand Down Expand Up @@ -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;
Expand Down