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![Vlastimil Babka](/assets/img/avatar_default.png)
Currently, enabling CONFIG_STACKDEPOT means its stack_table will be allocated from memblock, even if stack depot ends up not actually used. The default size of stack_table is 4MB on 32-bit, 8MB on 64-bit. This is fine for use-cases such as KASAN which is also a config option and has overhead on its own. But it's an issue for functionality that has to be actually enabled on boot (page_owner) or depends on hardware (GPU drivers) and thus the memory might be wasted. This was raised as an issue [1] when attempting to add stackdepot support for SLUB's debug object tracking functionality. It's common to build kernels with CONFIG_SLUB_DEBUG and enable slub_debug on boot only when needed, or create only specific kmem caches with debugging for testing purposes. It would thus be more efficient if stackdepot's table was allocated only when actually going to be used. This patch thus makes the allocation (and whole stack_depot_init() call) optional: - Add a CONFIG_STACKDEPOT_ALWAYS_INIT flag to keep using the current well-defined point of allocation as part of mem_init(). Make CONFIG_KASAN select this flag. - Other users have to call stack_depot_init() as part of their own init when it's determined that stack depot will actually be used. This may depend on both config and runtime conditions. Convert current users which are page_owner and several in the DRM subsystem. Same will be done for SLUB later. - Because the init might now be called after the boot-time memblock allocation has given all memory to the buddy allocator, change stack_depot_init() to allocate stack_table with kvmalloc() when memblock is no longer available. Also handle allocation failure by disabling stackdepot (could have theoretically happened even with memblock allocation previously), and don't unnecessarily align the memblock allocation to its own size anymore. [1] https://lore.kernel.org/all/CAMuHMdW=eoVzM1Re5FVoEN87nKfiLmM2+Ah7eNu2KXEhCvbZyA@mail.gmail.com/ Link: https://lkml.kernel.org/r/20211013073005.11351-1-vbabka@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Marco Elver <elver@google.com> # stackdepot Cc: Marco Elver <elver@google.com> Cc: Vijayanand Jitta <vjitta@codeaurora.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Oliver Glitta <glittao@gmail.com> Cc: Imran Khan <imran.f.khan@oracle.com> From: Colin Ian King <colin.king@canonical.com> Subject: lib/stackdepot: fix spelling mistake and grammar in pr_err message There is a spelling mistake of the work allocation so fix this and re-phrase the message to make it easier to read. Link: https://lkml.kernel.org/r/20211015104159.11282-1-colin.king@canonical.com Signed-off-by: Colin Ian King <colin.king@canonical.com> Cc: Vlastimil Babka <vbabka@suse.cz> From: Vlastimil Babka <vbabka@suse.cz> Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup On FLATMEM, we call page_ext_init_flatmem_late() just before kmem_cache_init() which means stack_depot_init() (called by page owner init) will not recognize properly it should use kvmalloc() and not memblock_alloc(). memblock_alloc() will also not issue a warning and return a block memory that can be invalid and cause kernel page fault when saving stacks, as reported by the kernel test robot [1]. Fix this by moving page_ext_init_flatmem_late() below kmem_cache_init() so that slab_is_available() is true during stack_depot_init(). SPARSEMEM doesn't have this issue, as it doesn't do page_ext_init_flatmem_late(), but a different page_ext_init() even later in the boot process. Thanks to Mike Rapoport for pointing out the FLATMEM init ordering issue. While at it, also actually resolve a checkpatch warning in stack_depot_init() from DRM CI, which was supposed to be in the original patch already. [1] https://lore.kernel.org/all/20211014085450.GC18719@xsang-OptiPlex-9020/ Link: https://lkml.kernel.org/r/6abd9213-19a9-6d58-cedc-2414386d2d81@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reported-by: kernel test robot <oliver.sang@intel.com> Cc: Mike Rapoport <rppt@kernel.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> From: Vlastimil Babka <vbabka@suse.cz> Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup3 Due tocd06ab2fd4
("drm/locking: add backtrace for locking contended locks without backoff") landing recently to -next adding a new stack depot user in drivers/gpu/drm/drm_modeset_lock.c we need to add an appropriate call to stack_depot_init() there as well. Link: https://lkml.kernel.org/r/2a692365-cfa1-64f2-34e0-8aa5674dce5e@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Cc: Jani Nikula <jani.nikula@intel.com> Cc: Naresh Kamboju <naresh.kamboju@linaro.org> Cc: Marco Elver <elver@google.com> Cc: Vijayanand Jitta <vjitta@codeaurora.org> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Maxime Ripard <mripard@kernel.org> Cc: Thomas Zimmermann <tzimmermann@suse.de> Cc: David Airlie <airlied@linux.ie> Cc: Daniel Vetter <daniel@ffwll.ch> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Oliver Glitta <glittao@gmail.com> Cc: Imran Khan <imran.f.khan@oracle.com> Cc: Stephen Rothwell <sfr@canb.auug.org.au> From: Vlastimil Babka <vbabka@suse.cz> Subject: lib/stackdepot: allow optional init and stack_table allocation by kvmalloc() - fixup4 Due to4e66934eaa
("lib: add reference counting tracking infrastructure") landing recently to net-next adding a new stack depot user in lib/ref_tracker.c we need to add an appropriate call to stack_depot_init() there as well. Link: https://lkml.kernel.org/r/45c1b738-1a2f-5b5f-2f6d-86fab206d01c@suse.cz Signed-off-by: Vlastimil Babka <vbabka@suse.cz> Reviewed-by: Eric Dumazet <edumazet@google.com> Cc: Jiri Slab <jirislaby@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
213 lines
7.3 KiB
Text
213 lines
7.3 KiB
Text
# SPDX-License-Identifier: GPL-2.0-only
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# This config refers to the generic KASAN mode.
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config HAVE_ARCH_KASAN
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bool
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config HAVE_ARCH_KASAN_SW_TAGS
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bool
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config HAVE_ARCH_KASAN_HW_TAGS
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bool
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config HAVE_ARCH_KASAN_VMALLOC
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bool
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config ARCH_DISABLE_KASAN_INLINE
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bool
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help
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An architecture might not support inline instrumentation.
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When this option is selected, inline and stack instrumentation are
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disabled.
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config CC_HAS_KASAN_GENERIC
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def_bool $(cc-option, -fsanitize=kernel-address)
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config CC_HAS_KASAN_SW_TAGS
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def_bool $(cc-option, -fsanitize=kernel-hwaddress)
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# This option is only required for software KASAN modes.
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# Old GCC versions don't have proper support for no_sanitize_address.
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# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124 for details.
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config CC_HAS_WORKING_NOSANITIZE_ADDRESS
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def_bool !CC_IS_GCC || GCC_VERSION >= 80300
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menuconfig KASAN
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bool "KASAN: runtime memory debugger"
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depends on (((HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC) || \
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(HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS)) && \
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CC_HAS_WORKING_NOSANITIZE_ADDRESS) || \
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HAVE_ARCH_KASAN_HW_TAGS
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depends on (SLUB && SYSFS) || (SLAB && !DEBUG_SLAB)
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select STACKDEPOT_ALWAYS_INIT
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help
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Enables KASAN (KernelAddressSANitizer) - runtime memory debugger,
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designed to find out-of-bounds accesses and use-after-free bugs.
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See Documentation/dev-tools/kasan.rst for details.
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if KASAN
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choice
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prompt "KASAN mode"
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default KASAN_GENERIC
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help
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KASAN has three modes:
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1. generic KASAN (similar to userspace ASan,
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x86_64/arm64/xtensa, enabled with CONFIG_KASAN_GENERIC),
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2. software tag-based KASAN (arm64 only, based on software
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memory tagging (similar to userspace HWASan), enabled with
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CONFIG_KASAN_SW_TAGS), and
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3. hardware tag-based KASAN (arm64 only, based on hardware
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memory tagging, enabled with CONFIG_KASAN_HW_TAGS).
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All KASAN modes are strictly debugging features.
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For better error reports enable CONFIG_STACKTRACE.
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config KASAN_GENERIC
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bool "Generic mode"
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depends on HAVE_ARCH_KASAN && CC_HAS_KASAN_GENERIC
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depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
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select SLUB_DEBUG if SLUB
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select CONSTRUCTORS
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help
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Enables generic KASAN mode.
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This mode is supported in both GCC and Clang. With GCC it requires
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version 8.3.0 or later. Any supported Clang version is compatible,
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but detection of out-of-bounds accesses for global variables is
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supported only since Clang 11.
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This mode consumes about 1/8th of available memory at kernel start
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and introduces an overhead of ~x1.5 for the rest of the allocations.
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The performance slowdown is ~x3.
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Currently CONFIG_KASAN_GENERIC doesn't work with CONFIG_DEBUG_SLAB
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(the resulting kernel does not boot).
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config KASAN_SW_TAGS
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bool "Software tag-based mode"
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depends on HAVE_ARCH_KASAN_SW_TAGS && CC_HAS_KASAN_SW_TAGS
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depends on CC_HAS_WORKING_NOSANITIZE_ADDRESS
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select SLUB_DEBUG if SLUB
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select CONSTRUCTORS
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help
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Enables software tag-based KASAN mode.
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This mode require software memory tagging support in the form of
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HWASan-like compiler instrumentation.
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Currently this mode is only implemented for arm64 CPUs and relies on
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Top Byte Ignore. This mode requires Clang.
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This mode consumes about 1/16th of available memory at kernel start
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and introduces an overhead of ~20% for the rest of the allocations.
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This mode may potentially introduce problems relating to pointer
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casting and comparison, as it embeds tags into the top byte of each
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pointer.
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Currently CONFIG_KASAN_SW_TAGS doesn't work with CONFIG_DEBUG_SLAB
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(the resulting kernel does not boot).
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config KASAN_HW_TAGS
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bool "Hardware tag-based mode"
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depends on HAVE_ARCH_KASAN_HW_TAGS
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depends on SLUB
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help
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Enables hardware tag-based KASAN mode.
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This mode requires hardware memory tagging support, and can be used
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by any architecture that provides it.
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Currently this mode is only implemented for arm64 CPUs starting from
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ARMv8.5 and relies on Memory Tagging Extension and Top Byte Ignore.
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endchoice
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choice
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prompt "Instrumentation type"
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depends on KASAN_GENERIC || KASAN_SW_TAGS
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default KASAN_OUTLINE
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config KASAN_OUTLINE
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bool "Outline instrumentation"
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help
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Before every memory access compiler insert function call
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__asan_load*/__asan_store*. These functions performs check
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of shadow memory. This is slower than inline instrumentation,
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however it doesn't bloat size of kernel's .text section so
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much as inline does.
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config KASAN_INLINE
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bool "Inline instrumentation"
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depends on !ARCH_DISABLE_KASAN_INLINE
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help
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Compiler directly inserts code checking shadow memory before
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memory accesses. This is faster than outline (in some workloads
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it gives about x2 boost over outline instrumentation), but
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make kernel's .text size much bigger.
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endchoice
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config KASAN_STACK
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bool "Enable stack instrumentation (unsafe)" if CC_IS_CLANG && !COMPILE_TEST
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depends on KASAN_GENERIC || KASAN_SW_TAGS
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depends on !ARCH_DISABLE_KASAN_INLINE
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default y if CC_IS_GCC
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help
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The LLVM stack address sanitizer has a know problem that
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causes excessive stack usage in a lot of functions, see
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https://bugs.llvm.org/show_bug.cgi?id=38809
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Disabling asan-stack makes it safe to run kernels build
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with clang-8 with KASAN enabled, though it loses some of
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the functionality.
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This feature is always disabled when compile-testing with clang
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to avoid cluttering the output in stack overflow warnings,
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but clang users can still enable it for builds without
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CONFIG_COMPILE_TEST. On gcc it is assumed to always be safe
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to use and enabled by default.
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If the architecture disables inline instrumentation, stack
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instrumentation is also disabled as it adds inline-style
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instrumentation that is run unconditionally.
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config KASAN_TAGS_IDENTIFY
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bool "Enable memory corruption identification"
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depends on KASAN_SW_TAGS || KASAN_HW_TAGS
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help
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This option enables best-effort identification of bug type
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(use-after-free or out-of-bounds) at the cost of increased
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memory consumption.
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config KASAN_VMALLOC
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bool "Back mappings in vmalloc space with real shadow memory"
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depends on KASAN_GENERIC && HAVE_ARCH_KASAN_VMALLOC
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help
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By default, the shadow region for vmalloc space is the read-only
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zero page. This means that KASAN cannot detect errors involving
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vmalloc space.
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Enabling this option will hook in to vmap/vmalloc and back those
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mappings with real shadow memory allocated on demand. This allows
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for KASAN to detect more sorts of errors (and to support vmapped
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stacks), but at the cost of higher memory usage.
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config KASAN_KUNIT_TEST
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tristate "KUnit-compatible tests of KASAN bug detection capabilities" if !KUNIT_ALL_TESTS
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depends on KASAN && KUNIT
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default KUNIT_ALL_TESTS
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help
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This is a KUnit test suite doing various nasty things like
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out of bounds and use after free accesses. It is useful for testing
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kernel debugging features like KASAN.
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For more information on KUnit and unit tests in general, please refer
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to the KUnit documentation in Documentation/dev-tools/kunit.
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config KASAN_MODULE_TEST
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tristate "KUnit-incompatible tests of KASAN bug detection capabilities"
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depends on m && KASAN && !KASAN_HW_TAGS
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help
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This is a part of the KASAN test suite that is incompatible with
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KUnit. Currently includes tests that do bad copy_from/to_user
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accesses.
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endif # KASAN
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