[PATCH] D14991: [ELF/AArch64] Print a diagnostic message if nonzero addend is used in a GOT relocation.

[Igor Kudrin via llvm-commits]

ikudrin added a comment.

In http://reviews.llvm.org/D14991#296701, @ruiu wrote:

> Do we really want to have this check? We don't have to check all possible ABI violations of input files. This is a kind of ABI violation that if you set an addend to a relocation, the output will have a value with that addend, which is a natural consequence.


As far as I can understand, it's not a violation of ABI rules in input files. See section "4.6.3 Relocation types" in http://infocenter.arm.com/help/topic/com.arm.doc.ihi0056b/IHI0056B_aaelf64.pdf:

> - GDAT(S+A) represents a 64-bit entry in the GOT for address S+A. The entry will be relocated at run time with relocation R_AARCH64_GLOB_DAT(S+A).

> - G(expr) is the address of the GOT entry for the expression expr.


And in section "4.6.6 Static AArch64 relocations", "Table 4-14, GOT-relative instruction relocations":

> R_AARCH64_ADR_GOT_PAGE: Page(G(GDAT(S+A))) - Page(P)

>  R_AARCH64_LD64_GOT_LO12_NC: G(GDAT(S+A))


So, the input is valid, but I'm doubt if it is in use or not. If we don't detect the situation we will //silently// produce broken executable file with bugs which are very hard to be caught. But if we print a message, it'll clearly point to the problem case.


http://reviews.llvm.org/D14991