[Feature] add GA346 baseline version
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+The Kernel Address Sanitizer (KASAN)
+====================================
+
+Overview
+--------
+
+KernelAddressSANitizer (KASAN) is a dynamic memory error detector designed to
+find out-of-bound and use-after-free bugs. KASAN has two modes: generic KASAN
+(similar to userspace ASan) and software tag-based KASAN (similar to userspace
+HWASan).
+
+KASAN uses compile-time instrumentation to insert validity checks before every
+memory access, and therefore requires a compiler version that supports that.
+
+Generic KASAN is supported in both GCC and Clang. With GCC it requires version
+4.9.2 or later for basic support and version 5.0 or later for detection of
+out-of-bounds accesses for stack and global variables and for inline
+instrumentation mode (see the Usage section). With Clang it requires version
+7.0.0 or later and it doesn't support detection of out-of-bounds accesses for
+global variables yet.
+
+Tag-based KASAN is only supported in Clang and requires version 7.0.0 or later.
+
+Currently generic KASAN is supported for the x86_64, arm64, xtensa and s390
+architectures, and tag-based KASAN is supported only for arm64.
+
+Usage
+-----
+
+To enable KASAN configure kernel with::
+
+ CONFIG_KASAN = y
+
+and choose between CONFIG_KASAN_GENERIC (to enable generic KASAN) and
+CONFIG_KASAN_SW_TAGS (to enable software tag-based KASAN).
+
+You also need to choose between CONFIG_KASAN_OUTLINE and 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 KASAN modes work with both SLUB and SLAB memory allocators.
+For better bug detection and nicer reporting, enable CONFIG_STACKTRACE.
+
+To disable instrumentation for specific files or directories, add a line
+similar to the following to the respective kernel Makefile:
+
+- For a single file (e.g. main.o)::
+
+ KASAN_SANITIZE_main.o := n
+
+- For all files in one directory::
+
+ KASAN_SANITIZE := n
+
+Error reports
+~~~~~~~~~~~~~
+
+A typical out-of-bounds access generic KASAN report looks like this::
+
+ ==================================================================
+ BUG: KASAN: slab-out-of-bounds in kmalloc_oob_right+0xa8/0xbc [test_kasan]
+ Write of size 1 at addr ffff8801f44ec37b by task insmod/2760
+
+ CPU: 1 PID: 2760 Comm: insmod Not tainted 4.19.0-rc3+ #698
+ Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
+ Call Trace:
+ dump_stack+0x94/0xd8
+ print_address_description+0x73/0x280
+ kasan_report+0x144/0x187
+ __asan_report_store1_noabort+0x17/0x20
+ kmalloc_oob_right+0xa8/0xbc [test_kasan]
+ kmalloc_tests_init+0x16/0x700 [test_kasan]
+ do_one_initcall+0xa5/0x3ae
+ do_init_module+0x1b6/0x547
+ load_module+0x75df/0x8070
+ __do_sys_init_module+0x1c6/0x200
+ __x64_sys_init_module+0x6e/0xb0
+ do_syscall_64+0x9f/0x2c0
+ entry_SYSCALL_64_after_hwframe+0x44/0xa9
+ RIP: 0033:0x7f96443109da
+ RSP: 002b:00007ffcf0b51b08 EFLAGS: 00000202 ORIG_RAX: 00000000000000af
+ RAX: ffffffffffffffda RBX: 000055dc3ee521a0 RCX: 00007f96443109da
+ RDX: 00007f96445cff88 RSI: 0000000000057a50 RDI: 00007f9644992000
+ RBP: 000055dc3ee510b0 R08: 0000000000000003 R09: 0000000000000000
+ R10: 00007f964430cd0a R11: 0000000000000202 R12: 00007f96445cff88
+ R13: 000055dc3ee51090 R14: 0000000000000000 R15: 0000000000000000
+
+ Allocated by task 2760:
+ save_stack+0x43/0xd0
+ kasan_kmalloc+0xa7/0xd0
+ kmem_cache_alloc_trace+0xe1/0x1b0
+ kmalloc_oob_right+0x56/0xbc [test_kasan]
+ kmalloc_tests_init+0x16/0x700 [test_kasan]
+ do_one_initcall+0xa5/0x3ae
+ do_init_module+0x1b6/0x547
+ load_module+0x75df/0x8070
+ __do_sys_init_module+0x1c6/0x200
+ __x64_sys_init_module+0x6e/0xb0
+ do_syscall_64+0x9f/0x2c0
+ entry_SYSCALL_64_after_hwframe+0x44/0xa9
+
+ Freed by task 815:
+ save_stack+0x43/0xd0
+ __kasan_slab_free+0x135/0x190
+ kasan_slab_free+0xe/0x10
+ kfree+0x93/0x1a0
+ umh_complete+0x6a/0xa0
+ call_usermodehelper_exec_async+0x4c3/0x640
+ ret_from_fork+0x35/0x40
+
+ The buggy address belongs to the object at ffff8801f44ec300
+ which belongs to the cache kmalloc-128 of size 128
+ The buggy address is located 123 bytes inside of
+ 128-byte region [ffff8801f44ec300, ffff8801f44ec380)
+ The buggy address belongs to the page:
+ page:ffffea0007d13b00 count:1 mapcount:0 mapping:ffff8801f7001640 index:0x0
+ flags: 0x200000000000100(slab)
+ raw: 0200000000000100 ffffea0007d11dc0 0000001a0000001a ffff8801f7001640
+ raw: 0000000000000000 0000000080150015 00000001ffffffff 0000000000000000
+ page dumped because: kasan: bad access detected
+
+ Memory state around the buggy address:
+ ffff8801f44ec200: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
+ ffff8801f44ec280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
+ >ffff8801f44ec300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03
+ ^
+ ffff8801f44ec380: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
+ ffff8801f44ec400: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
+ ==================================================================
+
+The header of the report provides a short summary of what kind of bug happened
+and what kind of access caused it. It's followed by a stack trace of the bad
+access, a stack trace of where the accessed memory was allocated (in case bad
+access happens on a slab object), and a stack trace of where the object was
+freed (in case of a use-after-free bug report). Next comes a description of
+the accessed slab object and information about the accessed memory page.
+
+In the last section the report shows memory state around the accessed address.
+Reading this part requires some understanding of how KASAN works.
+
+The state of each 8 aligned bytes of memory is encoded in one shadow byte.
+Those 8 bytes can be accessible, partially accessible, freed or be a redzone.
+We use the following encoding for each shadow byte: 0 means that all 8 bytes
+of the corresponding memory region are accessible; number N (1 <= N <= 7) means
+that the first N bytes are accessible, and other (8 - N) bytes are not;
+any negative value indicates that the entire 8-byte word is inaccessible.
+We use different negative values to distinguish between different kinds of
+inaccessible memory like redzones or freed memory (see mm/kasan/kasan.h).
+
+In the report above the arrows point to the shadow byte 03, which means that
+the accessed address is partially accessible.
+
+For tag-based KASAN this last report section shows the memory tags around the
+accessed address (see Implementation details section).
+
+
+Implementation details
+----------------------
+
+Generic KASAN
+~~~~~~~~~~~~~
+
+From a high level, our approach to memory error detection is similar to that
+of kmemcheck: use shadow memory to record whether each byte of memory is safe
+to access, and use compile-time instrumentation to insert checks of shadow
+memory on each memory access.
+
+Generic KASAN dedicates 1/8th of kernel memory to its shadow memory (e.g. 16TB
+to cover 128TB on x86_64) and uses direct mapping with a scale and offset to
+translate a memory address to its corresponding shadow address.
+
+Here is the function which translates an address to its corresponding shadow
+address::
+
+ static inline void *kasan_mem_to_shadow(const void *addr)
+ {
+ return ((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT)
+ + KASAN_SHADOW_OFFSET;
+ }
+
+where ``KASAN_SHADOW_SCALE_SHIFT = 3``.
+
+Compile-time instrumentation is used to insert memory access checks. Compiler
+inserts function calls (__asan_load*(addr), __asan_store*(addr)) before each
+memory access of size 1, 2, 4, 8 or 16. These functions check whether memory
+access is valid or not by checking corresponding shadow memory.
+
+GCC 5.0 has possibility to perform inline instrumentation. Instead of making
+function calls GCC directly inserts the code to check the shadow memory.
+This option significantly enlarges kernel but it gives x1.1-x2 performance
+boost over outline instrumented kernel.
+
+Software tag-based KASAN
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+Tag-based KASAN uses the Top Byte Ignore (TBI) feature of modern arm64 CPUs to
+store a pointer tag in the top byte of kernel pointers. Like generic KASAN it
+uses shadow memory to store memory tags associated with each 16-byte memory
+cell (therefore it dedicates 1/16th of the kernel memory for shadow memory).
+
+On each memory allocation tag-based KASAN generates a random tag, tags the
+allocated memory with this tag, and embeds this tag into the returned pointer.
+Software tag-based KASAN uses compile-time instrumentation to insert checks
+before each memory access. These checks make sure that tag of the memory that
+is being accessed is equal to tag of the pointer that is used to access this
+memory. In case of a tag mismatch tag-based KASAN prints a bug report.
+
+Software tag-based KASAN also has two instrumentation modes (outline, that
+emits callbacks to check memory accesses; and inline, that performs the shadow
+memory checks inline). With outline instrumentation mode, a bug report is
+simply printed from the function that performs the access check. With inline
+instrumentation a brk instruction is emitted by the compiler, and a dedicated
+brk handler is used to print bug reports.
+
+A potential expansion of this mode is a hardware tag-based mode, which would
+use hardware memory tagging support instead of compiler instrumentation and
+manual shadow memory manipulation.