When implementing shims and executable blob for various confidential computing platforms like Intel SGX, AMD SEV-SNP and probably also upcoming ARMv9 REALMS, you often need to markup segments so that the loader knows to do how to do the "right thing". For instance, SGX has so called Thread Control Structure (TCS) pages, which are essentially entry points to the "enclaves", which is just a fancy name for executable blobs. TCS pages are contained within the enclave address space but need to be initialized in a special manner, so you need to hint the loader, which data segments contain them. Two ways that I know how to do that are both somewhat ugly hacks: 1. Use spare flags in p_flags. 2. Create a PT_NOTE with a name "TCS" and use p_descz to describe an offset. This is limits of course to 32-bit offset unless you pick from these to bad malwareish choices: a. Overwrite p_type with the other part of the address. b. Use two PT_NOTE entries for high and low parts of the address. I came up with solution that should be technically possible to implement in GCC that would scale all these needs and would not need anything substantially huge. I would be like to be able to do PT_NOTE's with a name formatted as follows: TCSxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Here x's represent zero padded hexadecimal offset of a label. Does GAS provide as of today something to "stringify" a label into address? If not, would that be something that could be added to GAS and GCC, or if it was contributed, would it be considered for upstream? There's dozens of similar cases in these technologies where this would solve the problem, so a solution that *specifically* sorts it out just for these TCS pages is not adequate. It was just one example. BR, Jarkko
