debug/elf: support relocations relative to sections with non-zero addresses

2020-08-31T18:42:38Z

commit 72ec930fa70c20ce69b21bf32a7916c04c2e9c2f added basic support for relocations, but assumed that the symbol value would be 0, likely because .debug_info always has address == 0 in the ELF section headers. CL 195679 added further support for relocations, but explicitly encoded the original assumption that section addresses would be 0. This change removes that assumption: all relocations will now be properly computed based on the target symbol value even when that symbol is a section with a non-zero address. Typically, sections that are part of a LOAD program segment have non-zero addresses. For example, .debug_ranges relocations could be relative to .text, which usually has an address > 0. Fixes #40879 Change-Id: Ib0a616bb8b05d6c96d179b03ca33a10946fc5d59 GitHub-Last-Rev: 4200de732641995f3a4958a13a5c78f65b7eae50 GitHub-Pull-Request: golang/go#41038 Reviewed-on: https://go-review.googlesource.com/c/go/+/250559 Run-TryBot: Ian Lance Taylor TryBot-Result: Gobot Gobot Reviewed-by: Ian Lance Taylor

go/src/debug/elf/testdata/multiple-code-sections.c, branch main

debug/elf: support relocations relative to sections with non-zero addresses