From e4e846b67df12045ee6554bfb568a89b4ed80a71 Mon Sep 17 00:00:00 2001 From: Mark Wielaard Date: Tue, 16 Jun 2015 14:05:35 +0200 Subject: [PATCH] libelf: Always call ftruncate before posix_fallocate to set the right size. When elf_update.c (write_file) doesn't know the current maximum file length it might have to reduce the file size. posix_fallocate can only extend the file. So always call ftruncate before that to set the file size and making sure the backing store is fully there. Add test cases for checking strip in place (eu-strip without -o) actually reduces the file size. But only for non-ET_REL files. We might not be able to strip ET_REL files (except when they are kernel modules) because they might contain "dangling" symbol table entries. https://bugzilla.redhat.com/show_bug.cgi?id=1232206 Signed-off-by: Mark Wielaard --- libelf/ChangeLog | 5 +++++ libelf/elf_update.c | 7 +++++-- tests/ChangeLog | 5 +++++ tests/run-strip-test.sh | 13 +++++++++++++ 4 files changed, 28 insertions(+), 2 deletions(-) diff --git a/libelf/ChangeLog b/libelf/ChangeLog index 30017cd..2d24007 100644 --- a/libelf/ChangeLog +++ b/libelf/ChangeLog @@ -1,3 +1,8 @@ +2015-06-16 Mark Wielaard + + * elf_update.c (write_file): Always also use ftruncate before + posix_fallocate to make sure file has the right size. + 2015-06-04 Mark Wielaard * elf_getdata.c (__libelf_type_aligns): Add entries for ELF_T_EHDR, diff --git a/libelf/elf_update.c b/libelf/elf_update.c index 9e34c46..9eb007b 100644 --- a/libelf/elf_update.c +++ b/libelf/elf_update.c @@ -60,15 +60,18 @@ write_file (Elf *elf, off_t size, int change_bo, size_t shnum) new file. We truncate the file later in this case. Note we use posix_fallocate to make sure the file content is really - there. Using ftruncate might mean the file is extended, but space + there. Only using ftruncate might mean the file is extended, but space isn't allocated yet. This might cause a SIGBUS once we write into the mmapped space and the disk is full. Using fallocate might fail on some file systems. posix_fallocate is required to extend the file and allocate enough space even if the underlying filesystem would - normally return EOPNOTSUPP. */ + normally return EOPNOTSUPP. Note that we do also need to ftruncate + in case the maximum_size isn't known and the file needs to be shorter + because posix_fallocate can only extend. */ if (elf->parent == NULL && (elf->maximum_size == ~((size_t) 0) || (size_t) size > elf->maximum_size) + && unlikely (ftruncate (elf->fildes, size) != 0) && unlikely (posix_fallocate (elf->fildes, 0, size) != 0)) { __libelf_seterrno (ELF_E_WRITE_ERROR); diff --git a/tests/ChangeLog b/tests/ChangeLog index 19878ac..34f89cc 100644 --- a/tests/ChangeLog +++ b/tests/ChangeLog @@ -1,3 +1,8 @@ +2015-06-16 Mark Wielaard + + * run-strip-test.sh: Add strip-in-place (eu-strip without -o) test + for non-ET_REL files. + 2015-05-30 Mark Wielaard * backtrace-subr.sh (check_native_core): Notice core file couldn't be diff --git a/tests/run-strip-test.sh b/tests/run-strip-test.sh index c558e90..2ebb5a9 100755 --- a/tests/run-strip-test.sh +++ b/tests/run-strip-test.sh @@ -49,6 +49,19 @@ testrun ${abs_top_builddir}/src/unstrip -o testfile.unstrip testfile.temp testfi testrun ${abs_top_builddir}/src/elfcmp --hash-inexact $original testfile.unstrip } +# Now strip in-place and make sure it is smaller. +# Skip ET_REL files, they might have unexpected symbol table entries. +is_ET_REL=0 +testrun ${abs_top_builddir}/src/readelf -h $original 2>&1 \ + | fgrep 'REL (Relocatable file)' && is_ET_REL=1 +if test $is_ET_REL -eq 0; then + SIZE_original=$(stat -c%s $original) + testrun ${abs_top_builddir}/src/strip $original + SIZE_stripped=$(stat -c%s $original) + test $SIZE_stripped -lt $SIZE_original || + { echo "*** failure in-place strip file not smaller $original"; status=1; } +fi + tempfiles testfile.sections testrun ${abs_top_builddir}/src/readelf -S testfile.temp > testfile.sections || status=$? fgrep ' .debug_' testfile.sections && status=1 -- 1.8.3.1