[PATCH] D129392: llvm-dwarfdump: Don't crash if DW_AT_{decl,call}_{file,line} uses signed form

[Pedro Alves via Phabricator via llvm-commits]

palves created this revision.
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The DWARF spec says:

Any debugging information entry representing the declaration of an object,
 module, subprogram or type may have DW_AT_decl_file, DW_AT_decl_line and
 DW_AT_decl_column attributes, each of whose value is an unsigned integer

  							 ^^^^^^^^

constant.

If however, a producer happens to emit DW_AT_decl_file /
DW_AT_decl_line using a signed integer form, llvm-dwarfdump crashes,
like so:

  (... snip ...)
  0x000000b4:   DW_TAG_structure_type
                  DW_AT_name      ("test_struct")
                  DW_AT_byte_size (136)
                  DW_AT_decl_file (llvm-dwarfdump: (... snip ...)/llvm/include/llvm/ADT/Optional.h:197: T& llvm::optional_detail::OptionalStorage<T, true>::getValue() &

[with T = long unsigned int]: Assertion `hasVal' failed.

  PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
  Stack dump:
  0.      Program arguments: /opt/rocm/llvm/bin/llvm-dwarfdump ./testsuite/outputs/gdb.rocm/lane-pc-vega20/lane-pc-vega20-kernel.so
   #0 0x000055cc8e78315f PrintStackTraceSignalHandler(void*) Signals.cpp:0:0
   #1 0x000055cc8e780d3d SignalHandler(int) Signals.cpp:0:0
   #2 0x00007f8f2cae8420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
   #3 0x00007f8f2c58d00b raise /build/glibc-SzIz7B/glibc-2.31/signal/../sysdeps/unix/sysv/linux/raise.c:51:1
   #4 0x00007f8f2c56c859 abort /build/glibc-SzIz7B/glibc-2.31/stdlib/abort.c:81:7
   #5 0x00007f8f2c56c729 get_sysdep_segment_value /build/glibc-SzIz7B/glibc-2.31/intl/loadmsgcat.c:509:8
   #6 0x00007f8f2c56c729 _nl_load_domain /build/glibc-SzIz7B/glibc-2.31/intl/loadmsgcat.c:970:34
   #7 0x00007f8f2c57dfd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
   #8 0x000055cc8e58ceb9 llvm::DWARFDie::dump(llvm::raw_ostream&, unsigned int, llvm::DIDumpOptions) const (/opt/rocm/llvm/bin/llvm-dwarfdump+0x2e0eb9)
   #9 0x000055cc8e58bec3 llvm::DWARFDie::dump(llvm::raw_ostream&, unsigned int, llvm::DIDumpOptions) const (/opt/rocm/llvm/bin/llvm-dwarfdump+0x2dfec3)
  #10 0x000055cc8e5b28a3 llvm::DWARFCompileUnit::dump(llvm::raw_ostream&, llvm::DIDumpOptions) (.part.21) DWARFCompileUnit.cpp:0:0

Likewise with DW_AT_call_file / DW_AT_call_line.

The problem is that the code in llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
dumping these attributes assumes that
FormValue.getAsUnsignedConstant() returns an armed optional.  If in
debug mode, we get an assertion line the above.  If in release mode,
and asserts are compiled out, then we proceed as if the optional had a
value, running into undefined behavior, printing whatever random
value.

Fix this by checking whether the optional returned by
FormValue.getAsUnsignedConstant() has a value, like done in other
places.

In addition, DWARFVerifier.cpp is validating DW_AT_call_file /
DW_AT_decl_file, but not AT_call_line / DW_AT_decl_line.  This commit
fixes that too.

The llvm-dwarfdump/X86/verify_file_encoding.yaml testcase is extended
to cover these cases.  Current llvm-dwarfdump crashes running the
newly-extended test.

"make check-llvm-tools-llvm-dwarfdump" shows no regressions, on x86-64
GNU/Linux.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129392

Files:
  llvm/lib/DebugInfo/DWARF/DWARFDie.cpp
  llvm/lib/DebugInfo/DWARF/DWARFVerifier.cpp
  llvm/test/tools/llvm-dwarfdump/X86/verify_file_encoding.yaml

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