Binaries without a .note.openbsd.ident section fail to execute. This note section is mentioned in the ELF man page as follows.
> .note This section holds information in the note section format > described below. This section is of type SHT_NOTE. No > attribute types are used. OpenBSD native executables usually > contain a .note.openbsd.ident section to identify themselves, > for the kernel to bypass any compatibility ELF binary emula- > tion tests when loading the file. The use of the word "usually" makes this read ambiguously to me. In that it's not clear if this note is present and/or required in all binaries. Examining binaries on my system it seems this note is indeed always present and from practise does seem to be required (removing it from binaries with objcopy -R causes execution to fail). The mention of "emulation" made we wonder if perhaps this was referring to the old compat_linux layer. Reviewing the history it seems this part of the man page is largely unchanged from it's import in V 1.1 which pre-dates the removal of compat_linux. Is this indeed a remnant? If so should an update with firmer wording be made, perhaps something like the following? Though I'm not really sure what in the underlying implantation this note represents in a post compat_linux removal world? diff --git a/share/man/man5/elf.5 b/share/man/man5/elf.5 index d22279f6738..aece235de6b 100644 --- a/share/man/man5/elf.5 +++ b/share/man/man5/elf.5 @@ -1026,10 +1026,9 @@ This section is of type .Dv SHT_NOTE . No attribute types are used. .Ox -native executables usually contain a +native executables must contain a .Sy .note.openbsd.ident -section to identify themselves, for the kernel to bypass any compatibility -ELF binary emulation tests when loading the file. +section to identify themselves. .It .plt This section holds the procedure linkage table. This section is of type
