Documentation/sparse: add hints about __CHECKER__

Several attributes depend on __CHECKER__, but previously there was no
clue in the tree about when __CHECKER__ might be defined. Add hints at
the most common places (__kernel, __user, __iomem, __bitwise) and in the
sparse documentation.

Link: https://lkml.kernel.org/r/20220310220927.245704-3-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: "Michael S . Tsirkin" <mst@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

doc: add link to sparse's home page/internal docs

Sparse's home page used to be a wiki (sparse.wiki.kernel.org)
but this wiki only contained a short intro and the release notes.
But nowadays, sparse's main page is sparse.docs.kernel.org,
which contains all what was in the wiki but also other documentation,
mainly oriented about sparse's internals.

So, add a link to this in the kernel documentation.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Link: https://lore.kernel.org/r/20200629161310.89783-1-luc.vanoostenryck@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

doc: update URL for sparse's tarballs

The URL given to get sparse's tarballs is sparse.wiki.kernel.org
but the wiki will is deprecated in favor of sparse.docs.kernel.org.

So, update this URL to the one where the tarballs can directly
be found.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Link: https://lore.kernel.org/r/20200621153330.54480-1-luc.vanoostenryck@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Remove references to dead website.

This fell into disrepair a while ago, and the majority of hits to the
snapshots were from bots, so it's more trouble to keep running than it's worth.

Signed-off-by: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/sparse: fix typo

Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

rcu: Remove SPARSE_RCU_POINTER Kconfig option

The sparse-based checking for non-RCU accesses to RCU-protected pointers
has been around for a very long time, and it is now the only type of
sparse-based checking that is optional. This commit therefore makes
it unconditional.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>

Improve sparse documentation

Add documentation of -DCONFIG_SPARSE_RCU_POINTER.
I started to add documentation of -D__CHECK_ENDIAN__ as well, but
discovered I'm too late; that's now enabled by default.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/sparse: drop __CHECK_ENDIAN__

It's no longer used.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Documentation/sparse: drop __bitwise__

We dropped __CHECK_ENDIAN__ so __bitwise__ is now an implementation
detail. People should use __bitwise everywhere.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

docs: sphinxify sparse.txt and move to dev-tools

Fold the sparse document into the development tools set; no changes to the
text itself beyond formatting.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>