[PATCH] Recognize and parse GNU Property notes.
Mon Oct 29 00:12:00 GMT 2018
On Fri, 2018-10-19 at 12:26 +0200, Mark Wielaard wrote:
> 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
> 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 tor
> 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
> 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,
> and GNU_PROPERTY_X86_FEATURE_1_AND types
> and GNU_PROPERTY_X86_FEATURE_1_SHSTK.
> Tests are added for extracting the note from sections or segments
> as set by gcc -fcf-protection.
I pushed this to master.
There is some other information that might come from these notes, but
there are various open questions about what, how and the backwards
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