[PATCH 0/9] kcsan: Add support for reporting observed value changes

[Marco Elver <elver@google.com>]

This series adds support for showing observed value changes in reports.
Several clean up and refactors of KCSAN reporting code are done as a
pre-requisite. An example of the new KCSAN reports:

	==================================================================
	BUG: KCSAN: data-race in test_kernel_read / test_kernel_write

	write to 0xffffffffc009a628 of 8 bytes by task 487 on cpu 0:
	 test_kernel_write+0x1d/0x30
	 access_thread+0x89/0xd0
	 kthread+0x23e/0x260
	 ret_from_fork+0x22/0x30

	read to 0xffffffffc009a628 of 8 bytes by task 488 on cpu 6:
	 test_kernel_read+0x10/0x20
	 access_thread+0x89/0xd0
	 kthread+0x23e/0x260
	 ret_from_fork+0x22/0x30

	value changed: 0x00000000000009a6 -> 0x00000000000009b2

	Reported by Kernel Concurrency Sanitizer on:
	CPU: 6 PID: 488 Comm: access_thread Not tainted 5.12.0-rc2+ #1
	Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
	==================================================================

On one hand this will help better understand "race of unknown origin"
(one stack trace only) reports, but also provides more information to
better understand normal data race reports like above where KCSAN also
detected a value change.

Changelog
---------

This series was originally prepared courtesy of Mark Rutland in
September 2020. Because KCSAN had a few minor changes since the original
draft of the series, it required a rebase and re-test. To not be
forgotten and get these changes in sooner than later, Mark kindly agreed
to me adopting the series and doing the rebase, a few minor tweaks, and
finally re-test.

Marco Elver (1):
  kcsan: Document "value changed" line

Mark Rutland (8):
  kcsan: Simplify value change detection
  kcsan: Distinguish kcsan_report() calls
  kcsan: Refactor passing watchpoint/other_info
  kcsan: Fold panic() call into print_report()
  kcsan: Refactor access_info initialization
  kcsan: Remove reporting indirection
  kcsan: Remove kcsan_report_type
  kcsan: Report observed value changes

 Documentation/dev-tools/kcsan.rst |  88 +++++++---------
 kernel/kcsan/core.c               |  53 ++++------
 kernel/kcsan/kcsan.h              |  39 ++++---
 kernel/kcsan/report.c             | 169 ++++++++++++++++--------------
 4 files changed, 162 insertions(+), 187 deletions(-)

-- 
2.31.1.295.g9ea45b61b8-goog