[PATCH] D85430: [llvm-readobj] - Refine logic of the symbol table locating in printRelocationsHelper().

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: jhenderson, MaskRay.
Herald added subscribers: rupprecht, emaste.
Herald added a reviewer: espindola.
Herald added a project: LLVM.
grimar requested review of this revision.

This removes the last `unwrapOrError` call from the `printRelocationsHelper`.

There is a little complexity because of `SHT_RELR/SHT_ANDROID_RELR` sections.
Normally, their `sh_link` is set to `0`, because such sections contains only relative relocations
and they do not need a symbol table to be associated with them.

Also, with `--raw-relr` there is no need to decode `RELR` relocations at all, hence we also do not need
to locate a symbol table too.

At the same time, the `SHT_RELR` gABI proposal (https://groups.google.com/forum/#!topic/generic-abi/bX460iggiKg)
says that sh_link field of the `SHT_RELR` section contains the index of the associated symbol table.

So this patch implements the following for `SHT_RELR/SHT_ANDROID_RELR` sections:

1. When the `--raw-relr` is specified, we do not attempt to locate a symbol table. It allows us to dump the section even ehen sh_link is broken.
2. Without the `--raw-relr`, we fall back to the common code that tries to locate a symbol table and reports a warning on a failure.

Related code, invoked by `printRelocationsHelper` was slightly updated.
(signatures has been changed to `Elf_Shdr *SymTab` -> `Elf_Shdr &SymTab`
to emphasise the requirement of a a non-null symtab).

Depends on D85303 <https://reviews.llvm.org/D85303>.


https://reviews.llvm.org/D85430

Files:
  llvm/test/tools/llvm-readobj/ELF/packed-relocs.test
  llvm/test/tools/llvm-readobj/ELF/relocations.test
  llvm/test/tools/llvm-readobj/ELF/relr-relocs.test
  llvm/tools/llvm-readobj/ELFDumper.cpp

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