The Executable and Linking Format (ELF) specification is part of the System V ABI. In 1995, The Santa Cruz Operation "purchased the UnixWare business from Novell". Rather than attempt to provide the complete history of UNIX System V here, suffice it to say that The SCO Group is a good source for the System V ABI.
However, we are concerned with SPARC compliance, so the place to start is SPARC Compliance Definition (SCD 2.4.1) CHAPTER 4: Object Files. Where that chapter mentions the "System V ABI", refer to the gABI maintained by The SCO Group. SCD also mentions the "System V ABI, SPARC Processor Supplement" for the 32-bit psABI.
As the System V ABI explains, there are three main types of object files. The type required by FSS is executable file.
If the ELF is not a SPARC program, then it is highly probable that FSS will indicate illegal_instruction exception.