GCC with -flto detects some (very) unlikely issues in error paths.
In theory getting the Ehdr from an Elf handle might fail. But in
most cases where __libelf_data_type is used, we already have the
Ehdr anyway. So simply pass that to __libelf_data_type. In the one
place where we don't have it yet, get it and check for failure
before calling __libelf_data_type.
Signed-off-by: Mark Wielaard <mark@klomp.org>
Check whether a section was gnu compressed and decompress it first
before trying to resolve relocations. Recompress it afterwards.
This found a bug in elf_compress_gnu which would use the "raw" file
contents even if the user had just created the section (copying over
the section from the original input file).
Add compressed ET_REL tests to run-strip-reloc.sh testcase.
Signed-off-by: Mark Wielaard <mark@klomp.org>
GNU Property notes are different from normal notes because they use
variable alignment/padding of their fields. They are 8 byte aligned,
but use 4 byte fields. The name is aligned at 4 bytes and padded so
that, the desc is aligned at 8 bytes. The whole note is padded to
8 bytes again. For normal notes all fields are both 4 bytes wide and
4 bytes aligned.
To recognize these new kind of ELF Notes a new Elf_Type is introduced,
ELF_T_NHDR8. This type is used in the xlate functions to determine
how to align and pad the various fields. Since the fields themselves
can now have different alignments we will have to keep track of the
current alignement and use either NOTE_ALIGN4 or NOTE_ALIGN8 to
determine the padding.
To set the correct Elf_Type on the Elf_Data we use either the section
sh_addralign or the segment p_align values. Assuming 8 means the
section or segment contains the new style notes, otherwise normal
notes.
When we cannot determine the "alignment" directly, like when parsing
special kernel sys files, we check the name "GNU" and type
"GNU_PROPERTY_TYPE_0" fields.
ebl_object_note now parses the new NT_GNU_PROPERTY_TYPE_0 and can
extract the GNU_PROPERTY_STACK_SIZE, GNU_PROPERTY_NO_COPY_ON_PROTECTED
and GNU_PROPERTY_X86_FEATURE_1_AND types GNU_PROPERTY_X86_FEATURE_1_IBT
and GNU_PROPERTY_X86_FEATURE_1_SHSTK.
Tests are added for extracting the note from sections or segments
as set by gcc -fcf-protection.
Signed-off-by: Mark Wielaard <mark@klomp.org>
Compressing a section that is already compressed is fine, but useless.
But it isn't possible to gnu compress (or decompress) a SHF_COMPRESSED
section since there is no state kept that would tell if the section was
first GNU compressed or first gabi compressed. Calling elf_compress_gnu
on a section and then calling elf_compress on it to decompress it twice
could cause a crash (the other way around is fine). Just disallow it.
https://sourceware.org/bugzilla/show_bug.cgi?id=23528
Signed-off-by: Mark Wielaard <mark@klomp.org>
lizhenlin