Lines Matching +full:hardware +full:- +full:based
1 .. SPDX-License-Identifier: GPL-2.0
8 --------
11 designed to find out-of-bounds and use-after-free bugs.
16 2. Software Tag-Based KASAN
17 3. Hardware Tag-Based KASAN
23 Software Tag-Based KASAN or SW_TAGS KASAN, enabled with CONFIG_KASAN_SW_TAGS,
26 using it for testing on memory-restricted devices with real workloads.
28 Hardware Tag-Based KASAN or HW_TAGS KASAN, enabled with CONFIG_KASAN_HW_TAGS,
29 is the mode intended to be used as an in-field memory bug detector or as a
37 The Generic and the Software Tag-Based modes are commonly referred to as the
38 software modes. The Software Tag-Based and the Hardware Tag-Based modes are
39 referred to as the tag-based modes.
42 -------
48 and loongarch, and the tag-based KASAN modes are supported only on arm64.
53 Software KASAN modes use compile-time instrumentation to insert validity checks
55 support for that. The Hardware Tag-Based mode relies on hardware to perform
62 Software Tag-Based KASAN requires GCC 11+
65 Hardware Tag-Based KASAN requires GCC 10+ or Clang 12+.
73 Software Tag-Based KASAN supports slab, page_alloc, vmalloc, and stack memory.
75 Hardware Tag-Based KASAN supports slab, page_alloc, and non-executable vmalloc
79 Hardware Tag-Based KASAN only supports SLUB.
82 -----
89 ``CONFIG_KASAN_SW_TAGS`` (to enable Software Tag-Based KASAN), and
90 ``CONFIG_KASAN_HW_TAGS`` (to enable Hardware Tag-Based KASAN).
113 - ``kasan.fault=report``, ``=panic``, or ``=panic_on_write`` controls whether
117 Hardware Tag-Based KASAN, ``kasan.fault=panic_on_write`` always panics on
120 Software and Hardware Tag-Based KASAN modes (see the section about various
123 - ``kasan.stacktrace=off`` or ``=on`` disables or enables alloc and free stack
125 - ``kasan.stack_ring_size=<number of entries>`` specifies the number of entries
128 Hardware Tag-Based KASAN mode is intended for use in production as a security
132 - ``kasan=off`` or ``=on`` controls whether KASAN is enabled (default: ``on``).
134 - ``kasan.mode=sync``, ``=async`` or ``=asymm`` controls whether KASAN
140 fault occurs, the information is stored in hardware (in the TFSR_EL1
141 register for arm64). The kernel periodically checks the hardware and
146 - ``kasan.write_only=off`` or ``kasan.write_only=on`` controls whether KASAN
149 - ``kasan.vmalloc=off`` or ``=on`` disables or enables tagging of vmalloc
152 - ``kasan.page_alloc.sample=<sampling interval>`` makes KASAN tag only every
158 Note that enabling this parameter makes Hardware Tag-Based KASAN skip checks
162 - ``kasan.page_alloc.sample.order=<minimum page order>`` specifies the minimum
175 BUG: KASAN: slab-out-of-bounds in kmalloc_oob_right+0xa8/0xbc [kasan_test]
178 CPU: 1 PID: 2760 Comm: insmod Not tainted 4.19.0-rc3+ #698
179 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
226 which belongs to the cache kmalloc-128 of size 128
228 128-byte region [ffff8801f44ec300, ffff8801f44ec380)
248 and a stack trace of where the object was freed (in case of a use-after-free
263 bytes are accessible, and other (8 - N) bytes are not; any negative value
264 indicates that the entire 8-byte word is inaccessible. KASAN uses different
271 For tag-based KASAN modes, this last report section shows the memory tags around
274 Note that KASAN bug titles (like ``slab-out-of-bounds`` or ``use-after-free``)
275 are best-effort: KASAN prints the most probable bug type based on the limited
305 ----------------------
311 safe to access and use compile-time instrumentation to insert shadow memory
329 Compile-time instrumentation is used to insert memory access checks. Compiler
336 enlarges the kernel, but it gives an x1.1-x2 performance boost over the
337 outline-instrumented kernel.
342 Software Tag-Based KASAN
345 Software Tag-Based KASAN uses a software memory tagging approach to checking
348 Software Tag-Based KASAN uses the Top Byte Ignore (TBI) feature of arm64 CPUs
350 to store memory tags associated with each 16-byte memory cell (therefore, it
353 On each memory allocation, Software Tag-Based KASAN generates a random tag, tags
357 Software Tag-Based KASAN uses compile-time instrumentation to insert checks
360 this memory. In case of a tag mismatch, Software Tag-Based KASAN prints a bug
363 Software Tag-Based KASAN also has two instrumentation modes (outline, which
370 Software Tag-Based KASAN uses 0xFF as a match-all pointer tag (accesses through
374 Hardware Tag-Based KASAN
377 Hardware Tag-Based KASAN is similar to the software mode in concept but uses
378 hardware memory tagging support instead of compiler instrumentation and
381 Hardware Tag-Based KASAN is currently only implemented for arm64 architecture
382 and based on both arm64 Memory Tagging Extension (MTE) introduced in ARMv8.5
387 access, hardware makes sure that the tag of the memory that is being accessed is
391 Hardware Tag-Based KASAN uses 0xFF as a match-all pointer tag (accesses through
395 If the hardware does not support MTE (pre ARMv8.5), Hardware Tag-Based KASAN
398 Note that enabling CONFIG_KASAN_HW_TAGS always results in in-kernel TBI being
399 enabled. Even when ``kasan.mode=off`` is provided or when the hardware does not
402 Hardware Tag-Based KASAN only reports the first found bug. After that, MTE tag
406 -------------
421 other areas - such as vmalloc and vmemmap space - a single read-only
422 page is mapped over the shadow area. This read-only shadow page
431 lives in vmalloc space, it will be shadowed by the read-only page, and
462 This will require changes in arch-specific code.
468 --------------
485 - For a single file (e.g., main.o)::
489 - For all files in one directory::
493 For software KASAN modes, to disable instrumentation on a per-function basis,
494 use the KASAN-specific ``__no_sanitize_address`` function attribute or the
497 Note that disabling compiler instrumentation (either on a per-file or a
498 per-function basis) makes KASAN ignore the accesses that happen directly in
500 indirectly (through calls to instrumented functions) or with Hardware
501 Tag-Based KASAN, which does not use compiler instrumentation.
508 For tag-based KASAN modes, to disable access checking, use
511 restoring the per-page KASAN tag via ``page_kasan_tag``/``page_kasan_tag_set``.
528 ok 28 - kmalloc_double_kzfree
534 not ok 5 - kmalloc_large_oob_right
540 not ok 28 - kmalloc_double_kzfree
545 ok 1 - kasan
549 not ok 1 - kasan
558 2. Built-In
560 With ``CONFIG_KUNIT`` built-in, the tests can be built-in as well.
561 In this case, the tests will run at boot as a late-init call.
565 With ``CONFIG_KUNIT`` and ``CONFIG_KASAN_KUNIT_TEST`` built-in, it is also
568 See `KUnit documentation <https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html>`_
569 for more up-to-date information on ``kunit_tool``.
571 .. _KUnit: https://www.kernel.org/doc/html/latest/dev-tools/kunit/index.html