* Dave Martin: > Hi there, > > Can you clarify a couple of points about the SysV ABI Linux > Extensions [1] for me? > > 1) Can there be more than one NT_GNU_PROPERTY_TYPE_0 note in a valid > ELF file? I think the answer should be "no".
Yes, if it has been produced by a link editors which does not about property notes. The ELF file still needs to be treated as valid, but the note should be ignored. > 2) Is is permissible for an ELF ET_EXEC or ET_DYN file that contains > an NT_GNU_PROPERTY_TYPE_0 property not to have a PT_GNU_PROPERTY phdrs > entry mapping it? Except for historical usage by RedHat (which > apparently can be worked round in userspace) it seems reasonable for > the answer to be "no", at least for Linux. Using an older link editor on a CET-enabled distribution will produce such binaries, too. The ELF file still needs to be treated as valid, but the property date should be ignored. > 3) Is it permissible for the PT_GNU_PROPERTY phdr (if present) to > map anything other than precisely one NT_GNU_PROPERTY_TYPE_0 > note? I think the answer should be "no". Correct. Additional processing logic in the link editor is needed. > 4) Is an NT_GNU_PROPERTY_TYPE_0 note allowed to contain two or more > properties with the same pr_type? I think the answer should be "no". H.J. needs to answer that. > 5) What's the rationale for sorting the properties by pr_type? I can > see this would make it easier for the linker to merge > NT_GNU_PROPERTY_TYPE_0 notes from different files, but I'm wondering > whether the kernel really needs to enforce the ordering when loading > an ELF. The kernel doesn't need to merge property lists together. Likewise. > 6) Do you have a view on the best way to define the Elf_Prop type in > headers? bfd elf-bfd.h seems to have elf_property, but this doesn't > follow the style of the public ELF headers. We should put it into <elf.h> in glibc. We don't want to rely on UAPI headers there because this version of <elf.h> is used in many places. Thanks, Florian
