The patch titled
Subject: kasan: docs: update overview section
has been added to the -mm tree. Its filename is
kasan-docs-update-overview-section.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kasan-docs-update-overview-section.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kasan-docs-update-overview-section.patch
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------------------------------------------------------
From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Subject: kasan: docs: update overview section
Update the "Overview" section in KASAN documentation:
- Outline main use cases for each mode.
- Mention that HW_TAGS mode need compiler support too.
- Move the part about SLUB/SLAB support from "Usage" to "Overview".
- Punctuation, readability, and other minor clean-ups.
Link: https://lkml.kernel.org/r/1486fba8514de3d7db2f47df2192db59228b0a7b.1615559068.git.andreyknvl@xxxxxxxxxx
Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/dev-tools/kasan.rst | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)
--- a/Documentation/dev-tools/kasan.rst~kasan-docs-update-overview-section
+++ a/Documentation/dev-tools/kasan.rst
@@ -11,17 +11,31 @@ designed to find out-of-bound and use-af
2. software tag-based KASAN (similar to userspace HWASan),
3. hardware tag-based KASAN (based on hardware memory tagging).
-Software KASAN modes (1 and 2) use compile-time instrumentation to insert
-validity checks before every memory access, and therefore require a compiler
+Generic KASAN is mainly used for debugging due to a large memory overhead.
+Software tag-based KASAN can be used for dogfood testing as it has a lower
+memory overhead that allows using it with real workloads. Hardware tag-based
+KASAN comes with low memory and performance overheads and, therefore, can be
+used in production. Either as an in-field memory bug detector or as a security
+mitigation.
+
+Software KASAN modes (#1 and #2) use compile-time instrumentation to insert
+validity checks before every memory access and, therefore, require a compiler
version that supports that.
-Generic KASAN is supported in both GCC and Clang. With GCC it requires version
+Generic KASAN is supported in GCC and Clang. With GCC, it requires version
8.3.0 or later. Any supported Clang version is compatible, but detection of
out-of-bounds accesses for global variables is only supported since Clang 11.
-Tag-based KASAN is only supported in Clang.
+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+.
-Currently generic KASAN is supported for the x86_64, arm, arm64, xtensa, s390
+Both software KASAN modes work with SLUB and SLAB memory allocators,
+while the hardware tag-based KASAN currently only supports SLUB.
+
+Currently, generic KASAN is supported for the x86_64, arm, arm64, xtensa, s390,
and riscv architectures, and tag-based KASAN modes are supported only for arm64.
Usage
@@ -39,9 +53,6 @@ For software modes, you also need to cho
CONFIG_KASAN_INLINE. Outline and inline are compiler instrumentation types.
The former produces smaller binary while the latter is 1.1 - 2 times faster.
-Both software KASAN modes work with both SLUB and SLAB memory allocators,
-while the hardware tag-based KASAN currently only support SLUB.
-
For better error reports that include stack traces, enable CONFIG_STACKTRACE.
To augment reports with last allocation and freeing stack of the physical page,
_
Patches currently in -mm which might be from andreyknvl@xxxxxxxxxx are
kasan-mm-fix-crash-with-hw_tags-and-debug_pagealloc.patch
kasan-fix-kasan_stack-dependency-for-hw_tags.patch
kasan-fix-per-page-tags-for-non-page_alloc-pages.patch
kasan-initialize-shadow-to-tag_invalid-for-sw_tags.patch
mm-kasan-dont-poison-boot-memory-with-tag-based-modes.patch
arm64-kasan-allow-to-init-memory-when-setting-tags.patch
kasan-init-memory-in-kasan_unpoison-for-hw_tags.patch
kasan-mm-integrate-page_alloc-init-with-hw_tags.patch
kasan-mm-integrate-slab-init_on_alloc-with-hw_tags.patch
kasan-mm-integrate-slab-init_on_free-with-hw_tags.patch
kasan-docs-clean-up-sections.patch
kasan-docs-update-overview-section.patch
kasan-docs-update-usage-section.patch
kasan-docs-update-error-reports-section.patch
kasan-docs-update-boot-parameters-section.patch
kasan-docs-update-generic-implementation-details-section.patch
kasan-docs-update-sw_tags-implementation-details-section.patch
kasan-docs-update-hw_tags-implementation-details-section.patch
kasan-docs-update-shadow-memory-section.patch
kasan-docs-update-ignoring-accesses-section.patch
kasan-docs-update-tests-section.patch
