5 files changed, 34 insertions, 7 deletions

diff --git a/Documentation/dev-tools/kasan.rst b/Documentation/dev-tools/kasan.rst
index 8089c559d339..7614a1fc30fa 100644
--- a/Documentation/dev-tools/kasan.rst
+++ b/Documentation/dev-tools/kasan.rst
@@ -30,7 +30,7 @@ Software tag-based KASAN mode is only supported in Clang.
 
 The hardware KASAN mode (#3) relies on hardware to perform the checks but
 still requires a compiler version that supports memory tagging instructions.
-This mode is supported in GCC 10+ and Clang 11+.
+This mode is supported in GCC 10+ and Clang 12+.
 
 Both software KASAN modes work with SLUB and SLAB memory allocators,
 while the hardware tag-based KASAN currently only supports SLUB.
@@ -206,6 +206,9 @@ additional boot parameters that allow disabling KASAN or controlling features:
   Asymmetric mode: a bad access is detected synchronously on reads and
   asynchronously on writes.
 
+- ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc
+  allocations (default: ``on``).
+
 - ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
   traces collection (default: ``on``).
 
@@ -279,8 +282,8 @@ Software tag-based KASAN uses 0xFF as a match-all pointer tag (accesses through
 pointers with the 0xFF pointer tag are not checked). The value 0xFE is currently
 reserved to tag freed memory regions.
 
-Software tag-based KASAN currently only supports tagging of slab and page_alloc
-memory.
+Software tag-based KASAN currently only supports tagging of slab, page_alloc,
+and vmalloc memory.
 
 Hardware tag-based KASAN
 ~~~~~~~~~~~~~~~~~~~~~~~~
@@ -303,8 +306,8 @@ Hardware tag-based KASAN uses 0xFF as a match-all pointer tag (accesses through
 pointers with the 0xFF pointer tag are not checked). The value 0xFE is currently
 reserved to tag freed memory regions.
 
-Hardware tag-based KASAN currently only supports tagging of slab and page_alloc
-memory.
+Hardware tag-based KASAN currently only supports tagging of slab, page_alloc,
+and VM_ALLOC-based vmalloc memory.
 
 If the hardware does not support MTE (pre ARMv8.5), hardware tag-based KASAN
 will not be enabled. In this case, all KASAN boot parameters are ignored.
@@ -319,6 +322,8 @@ checking gets disabled.
 Shadow memory
 -------------
 
+The contents of this section are only applicable to software KASAN modes.
+
 The kernel maps memory in several different parts of the address space.
 The range of kernel virtual addresses is large: there is not enough real
 memory to support a real shadow region for every address that could be
@@ -349,7 +354,7 @@ CONFIG_KASAN_VMALLOC
 
 With ``CONFIG_KASAN_VMALLOC``, KASAN can cover vmalloc space at the
 cost of greater memory usage. Currently, this is supported on x86,
-riscv, s390, and powerpc.
+arm64, riscv, s390, and powerpc.
 
 This works by hooking into vmalloc and vmap and dynamically
 allocating real shadow memory to back the mappings.
diff --git a/Documentation/dev-tools/kfence.rst b/Documentation/dev-tools/kfence.rst
index ac6b89d1a8c3..936f6aaa75c8 100644
--- a/Documentation/dev-tools/kfence.rst
+++ b/Documentation/dev-tools/kfence.rst
@@ -41,6 +41,18 @@ guarded by KFENCE. The default is configurable via the Kconfig option
 ``CONFIG_KFENCE_SAMPLE_INTERVAL``. Setting ``kfence.sample_interval=0``
 disables KFENCE.
 
+The sample interval controls a timer that sets up KFENCE allocations. By
+default, to keep the real sample interval predictable, the normal timer also
+causes CPU wake-ups when the system is completely idle. This may be undesirable
+on power-constrained systems. The boot parameter ``kfence.deferrable=1``
+instead switches to a "deferrable" timer which does not force CPU wake-ups on
+idle systems, at the risk of unpredictable sample intervals. The default is
+configurable via the Kconfig option ``CONFIG_KFENCE_DEFERRABLE``.
+
+.. warning::
+   The KUnit test suite is very likely to fail when using a deferrable timer
+   since it currently causes very unpredictable sample intervals.
+
 The KFENCE memory pool is of fixed size, and if the pool is exhausted, no
 further KFENCE allocations occur. With ``CONFIG_KFENCE_NUM_OBJECTS`` (default
 255), the number of available guarded objects can be controlled. Each object
diff --git a/Documentation/dev-tools/kselftest.rst b/Documentation/dev-tools/kselftest.rst
index dcefee707ccd..a833ecf12fbc 100644
--- a/Documentation/dev-tools/kselftest.rst
+++ b/Documentation/dev-tools/kselftest.rst
@@ -7,6 +7,14 @@ directory. These are intended to be small tests to exercise individual code
 paths in the kernel. Tests are intended to be run after building, installing
 and booting a kernel.
 
+Kselftest from mainline can be run on older stable kernels. Running tests
+from mainline offers the best coverage. Several test rings run mainline
+kselftest suite on stable releases. The reason is that when a new test
+gets added to test existing code to regression test a bug, we should be
+able to run that test on an older kernel. Hence, it is important to keep
+code that can still test an older kernel and make sure it skips the test
+gracefully on newer releases.
+
 You can find additional information on Kselftest framework, how to
 write new tests using the framework on Kselftest wiki:
 
diff --git a/Documentation/dev-tools/kunit/usage.rst b/Documentation/dev-tools/kunit/usage.rst
index 76af931a332c..1c83e7d60a8a 100644
--- a/Documentation/dev-tools/kunit/usage.rst
+++ b/Documentation/dev-tools/kunit/usage.rst
@@ -242,7 +242,7 @@ example:
 
 	int rectangle_area(struct shape *this)
 	{
-		struct rectangle *self = container_of(this, struct shape, parent);
+		struct rectangle *self = container_of(this, struct rectangle, parent);
 
 		return self->length * self->width;
 	};
diff --git a/Documentation/dev-tools/sparse.rst b/Documentation/dev-tools/sparse.rst
index 02102be7ff49..dc791c8d84d1 100644
--- a/Documentation/dev-tools/sparse.rst
+++ b/Documentation/dev-tools/sparse.rst
@@ -100,3 +100,5 @@ have already built it.
 
 The optional make variable CF can be used to pass arguments to sparse.  The
 build system passes -Wbitwise to sparse automatically.
+
+Note that sparse defines the __CHECKER__ preprocessor symbol.