[PATCH] D39548: [ELF] Set the section size on the section start symbols

[Peter Smith via Phabricator via llvm-commits]

peter.smith added a comment.

Can you share a bit more about how CHERI uses the symbol size? Is it only for known linker generated Sections like in your example above, or to support arbitrary user mysection_start symbols? Is the mysection_start symbol special cased within CHERI or is it just an arbitrary ELF Symbol. I'm just a bit curious about the implications of setting the symbol size, for example if this is for special sections like .dynamic we would only expect the _start and _end, and _DYNAMIC symbols to be defined, in an arbitrary mysection_start there could be multiple other symbols defined as well and having the symbol size set to the section size would mean its [0, size)  range would overlap all other symbols in the section, this could potentially confuse other ELF processing tools that might skip over functions/data based on Symbol Size. I'm also curious as to how the symbol size is used? Does the OS/loader require the static symbol table to be present, what if it has been stripped?

On the assumption that there is a good reason for CHERI to use the symbol size I have some suggestions for the code.

- Given that addOptionalRegular is only used for start and end symbols and only uses the (now two) special cases of 0 and -1, I think we should rename the function to make it more specific to the purpose it is being used for.
- Would it be better to use a similar trick for Size as Value, for example if Size is -1 and symbol is defined with respect to an OutputSection then Size is Size of OutputSection? You'd then not need to track the state of the section symbols and have a potentially fragile one off update.


https://reviews.llvm.org/D39548