[PATCH] D88228: [yaml2obj][obj2yaml] - Add a support for SHT_ARM_EXIDX section.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
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[yaml2obj][obj2yaml] - Add a support for SHT_ARM_EXIDX section.

This adds the support for SHT_ARM_EXIDX sections to obj2yaml/yaml2obj tools.

SHT_ARM_EXIDX is a ARM specific index table filled with entries.
Each entry consists of two 4-bytes values (words).
(https://developer.arm.com/documentation/ihi0038/c/?lang=en#index-table-entries)

Note: I am not sure if we should respect endianness for these words.
This patch does. But seems everywhere in LLVM they are written/read as LE.
At the same time GNU readelf -u behaves differently for a section that is described as:

  - Name:    .ARM.exidx
    Type:    SHT_ARM_EXIDX
    Content: "00000000000000010000000001000000"

For a little endian object it dumps:

  > readelf -u test.o
  
  Unwind section '.ARM.exidx' at offset 0x40 contains 1 entry:
  
  0x0: @0x1000004
  readelf: Warning: Could not locate .ARM.extab section containing 0x1000004.
  
  0x8: 0x1 [cantunwind]

And for a big endian:

  > readelf -u test.o
  
  Unwind section '.ARM.exidx' at offset 0x40 contains 1 entry:
  
  0x0: 0x1 [cantunwind]
  
  0x8: @0x100000c
  readelf: Warning: Could not locate .ARM.extab section containing 0x100000c.

I also haven't found in specification that these values must always be little-endian.


https://reviews.llvm.org/D88228

Files:
  llvm/include/llvm/ObjectYAML/ELFYAML.h
  llvm/lib/ObjectYAML/ELFEmitter.cpp
  llvm/lib/ObjectYAML/ELFYAML.cpp
  llvm/test/tools/obj2yaml/ELF/arm-exidx-section.yaml
  llvm/test/tools/yaml2obj/ELF/arm-exidx-section.yaml
  llvm/tools/obj2yaml/elf2yaml.cpp

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