[PATCH v4 0/3] gcov: add Clang support

[Tri Vo <trong@android.com>]

This patch series adds Clang support for gcov.

Patch 1 refactors existing code in preparation for Clang support.
Patch 2 implements necessary LLVM runtime hooks and gcov kernel interfaces.
Patch 3 updates documentation.

Greg Hackmann (2):
  gcov: Clang: move common GCC code into gcc_base.c
  gcov: Clang support

Tri Vo (1):
  gcov: docs: add a note on GCC vs Clang differences

 Documentation/dev-tools/gcov.rst |  18 +-
 kernel/gcov/Kconfig              |   3 +-
 kernel/gcov/Makefile             |   5 +-
 kernel/gcov/base.c               |  86 +----
 kernel/gcov/clang.c              | 586 +++++++++++++++++++++++++++++++
 kernel/gcov/gcc_3_4.c            |  12 +
 kernel/gcov/gcc_4_7.c            |  12 +
 kernel/gcov/gcc_base.c           |  86 +++++
 kernel/gcov/gcov.h               |   5 +
 9 files changed, 723 insertions(+), 90 deletions(-)
 create mode 100644 kernel/gcov/clang.c
 create mode 100644 kernel/gcov/gcc_base.c

v2:
- Reorganized config dependencies, as per Masahiro.

v3:
- Squashed patches 2-4 of v2, as per Nick, Masahiro, and Peter.
Addressed comments by Peter:
- Moved __gcov_exit() to gcc_base.c
- Added missing header to gcc_base.c
- Removed unnecessary boundary checks in gcov_info_add().
- Changed counters' allocation to use vmalloc().
- Added check for failed allocation of filename.
- Changed list_for_each_entry_safe to list_for_each_entry when traversing
  without modifying.
- Updated Documentation/dev-tools/gcov.rst

v4:
Made following changes to pass kernel module test cases suggested by Peter:
- Generic code in base.c unlinks gcov_info data sets while iterating over
  the gcov_info list. Changed Clang's gcov_info_unlink() to preserve next
  and prev links of the unlinked gcov_info instance.
- Attributing a given gcov_info to a module is done differently in Clang vs
  GCC. Generic code in base.c needs to do this. So added
  gcov_info_within_module() interface to gcov.h to abstract away the
  difference.
- Clang provides checksums for each function. These checksums are used to
  determine whether the source files of the compiled kernel module have
  been modified. Changed gcov_info_is_compatible() to account for
  function-level checksums.
Addressed comments by Peter:
- Removed unnecessary #define, if-clause, empty line.
- Amended commit message to note documentation was adjusted to account for
  the removal of config symbol CONFIG_GCOV_FORMAT_AUTODETECT.

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2.21.0.225.g810b269d1ac-goog