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Sat, 06 Sep 2025 10:19:44 -0700 (PDT) MIME-Version: 1.0 References: <3db48135aec987c99e8e6601249d4a4c023703c4.1756151769.git.maciej.wieczor-retman@intel.com> In-Reply-To: <3db48135aec987c99e8e6601249d4a4c023703c4.1756151769.git.maciej.wieczor-retman@intel.com> From: Andrey Konovalov Date: Sat, 6 Sep 2025 19:19:33 +0200 X-Gm-Features: AS18NWARCvbmNO2W6P1AIa0UmJPeNw-mXWqtKJ3IgauS5o9YHYHKl3h4kKJN_64 Message-ID: Subject: Re: [PATCH v5 19/19] x86: Make software tag-based kasan available To: Maciej Wieczor-Retman Cc: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, jhubbard@nvidia.com, bp@alien8.de, x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: dotiqdcnzaru3u1e6ozzwfr4g6qyxpfu X-Rspam-User: X-Rspamd-Queue-Id: E607940004 X-Rspamd-Server: rspam01 X-HE-Tag: 1757179185-864343 X-HE-Meta: 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 boTKZ/qJ xC5sqL/F/h9C+bw0rjQpwEJtmaCGn5u/FQkN9S6Jgovun+2JGVWnwG109LX7h18Ab2/K7fysUyjhMTIlvGcfsBSR7XHT0wv+BxBnk1CL08zNTXC7kozWZUpw85eFzVZsrv3su2JGeggK6HJhKIZeps9bA/huw3uWoeBOXQDCNQR9azfKOCGINvLft83NpJmrr8kbARjlfht09TmC1LYvDTonXhtx2mnx4ygqP44ftBAoLr7Gbc2X0el2T5KpNTsMNrpY0e1xWQ1xBx7KYdQ3FG9dt/BQZKl++0txO+qtEfB7zvsoTJDkQAg3g183CVbblQZu6O7hRmCyv05pJ30wOei8SrGfLT7t9gZUEM8eLlkR9lkc8ds0682NvseoRPjHp2tQpHR7MfHA4oeikWtc6wR7yDjVMKeI5H/zncJcxM0K7MBVDoNtSY9Gxw1DBgfRmWBU5U1Q4TnpK940= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 25, 2025 at 10:32=E2=80=AFPM Maciej Wieczor-Retman wrote: > > Make CONFIG_KASAN_SW_TAGS available for x86 machines if they have > ADDRESS_MASKING enabled (LAM) as that works similarly to Top-Byte Ignore > (TBI) that allows the software tag-based mode on arm64 platform. > > Set scale macro based on KASAN mode: in software tag-based mode 16 bytes > of memory map to one shadow byte and 8 in generic mode. > > Disable CONFIG_KASAN_INLINE and CONFIG_KASAN_STACK when > CONFIG_KASAN_SW_TAGS is enabled on x86 until the appropriate compiler > support is available. > > Signed-off-by: Maciej Wieczor-Retman > --- > Changelog v4: > - Add x86 specific kasan_mem_to_shadow(). > - Revert x86 to the older unsigned KASAN_SHADOW_OFFSET. Do the same to > KASAN_SHADOW_START/END. > - Modify scripts/gdb/linux/kasan.py to keep x86 using unsigned offset. > - Disable inline and stack support when software tags are enabled on > x86. > > Changelog v3: > - Remove runtime_const from previous patch and merge the rest here. > - Move scale shift definition back to header file. > - Add new kasan offset for software tag based mode. > - Fix patch message typo 32 -> 16, and 16 -> 8. > - Update lib/Kconfig.kasan with x86 now having software tag-based > support. > > Changelog v2: > - Remove KASAN dense code. > > Documentation/arch/x86/x86_64/mm.rst | 6 ++++-- > arch/x86/Kconfig | 4 +++- > arch/x86/boot/compressed/misc.h | 1 + > arch/x86/include/asm/kasan.h | 1 + > arch/x86/kernel/setup.c | 2 ++ > lib/Kconfig.kasan | 3 ++- > scripts/gdb/linux/kasan.py | 4 ++-- > 7 files changed, 15 insertions(+), 6 deletions(-) > > diff --git a/Documentation/arch/x86/x86_64/mm.rst b/Documentation/arch/x8= 6/x86_64/mm.rst > index a6cf05d51bd8..ccbdbb4cda36 100644 > --- a/Documentation/arch/x86/x86_64/mm.rst > +++ b/Documentation/arch/x86/x86_64/mm.rst > @@ -60,7 +60,8 @@ Complete virtual memory map with 4-level page tables > ffffe90000000000 | -23 TB | ffffe9ffffffffff | 1 TB | ... unus= ed hole > ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual = memory map (vmemmap_base) > ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unus= ed hole > - ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN sh= adow memory > + ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN sh= adow memory (generic mode) > + fffff40000000000 | -8 TB | fffffbffffffffff | 8 TB | KASAN sh= adow memory (software tag-based mode) > __________________|____________|__________________|_________|_________= ___________________________________________________ > | > | Identica= l layout to the 56-bit one from here on: > @@ -130,7 +131,8 @@ Complete virtual memory map with 5-level page tables > ffd2000000000000 | -11.5 PB | ffd3ffffffffffff | 0.5 PB | ... unus= ed hole > ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual = memory map (vmemmap_base) > ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unus= ed hole > - ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN sh= adow memory > + ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN sh= adow memory (generic mode) > + ffeffc0000000000 | -6 PB | fffffbffffffffff | 4 PB | KASAN sh= adow memory (software tag-based mode) > __________________|____________|__________________|_________|_________= ___________________________________________________ > | > | Identica= l layout to the 47-bit one from here on: > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index b8df57ac0f28..f44fec1190b6 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -69,6 +69,7 @@ config X86 > select ARCH_CLOCKSOURCE_INIT > select ARCH_CONFIGURES_CPU_MITIGATIONS > select ARCH_CORRECT_STACKTRACE_ON_KRETPROBE > + select ARCH_DISABLE_KASAN_INLINE if X86_64 && KASAN_SW_TAG= S Do you think it would make sense to drop the parts of the series that add int3 handling, since the inline instrumentation does not work yet anyway? > select ARCH_ENABLE_HUGEPAGE_MIGRATION if X86_64 && HUGETLB_PAGE &= & MIGRATION > select ARCH_ENABLE_MEMORY_HOTPLUG if X86_64 > select ARCH_ENABLE_MEMORY_HOTREMOVE if MEMORY_HOTPLUG > @@ -199,6 +200,7 @@ config X86 > select HAVE_ARCH_JUMP_LABEL_RELATIVE > select HAVE_ARCH_KASAN if X86_64 > select HAVE_ARCH_KASAN_VMALLOC if X86_64 > + select HAVE_ARCH_KASAN_SW_TAGS if ADDRESS_MASKING > select HAVE_ARCH_KFENCE > select HAVE_ARCH_KMSAN if X86_64 > select HAVE_ARCH_KGDB > @@ -403,7 +405,7 @@ config AUDIT_ARCH > > config KASAN_SHADOW_OFFSET > hex > - depends on KASAN Line accidentally removed? > + default 0xeffffc0000000000 if KASAN_SW_TAGS > default 0xdffffc0000000000 > > config HAVE_INTEL_TXT > diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/m= isc.h > index db1048621ea2..ded92b439ada 100644 > --- a/arch/x86/boot/compressed/misc.h > +++ b/arch/x86/boot/compressed/misc.h > @@ -13,6 +13,7 @@ > #undef CONFIG_PARAVIRT_SPINLOCKS > #undef CONFIG_KASAN > #undef CONFIG_KASAN_GENERIC > +#undef CONFIG_KASAN_SW_TAGS > > #define __NO_FORTIFY > > diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h > index f3e34a9754d2..385f4e9daab3 100644 > --- a/arch/x86/include/asm/kasan.h > +++ b/arch/x86/include/asm/kasan.h > @@ -7,6 +7,7 @@ > #include > #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) > #ifdef CONFIG_KASAN_SW_TAGS > +#define KASAN_SHADOW_SCALE_SHIFT 4 > > /* > * LLVM ABI for reporting tag mismatches in inline KASAN mode. > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index 1b2edd07a3e1..5b819f84f6db 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -1207,6 +1207,8 @@ void __init setup_arch(char **cmdline_p) > > kasan_init(); > > + kasan_init_sw_tags(); > + > /* > * Sync back kernel address range. > * > diff --git a/lib/Kconfig.kasan b/lib/Kconfig.kasan > index f82889a830fa..9ddbc6aeb5d5 100644 > --- a/lib/Kconfig.kasan > +++ b/lib/Kconfig.kasan > @@ -100,7 +100,8 @@ config KASAN_SW_TAGS > > Requires GCC 11+ or Clang. > > - Supported only on arm64 CPUs and relies on Top Byte Ignore. > + Supported on arm64 CPUs that support Top Byte Ignore and on x86= CPUs > + that support Linear Address Masking. > > Consumes about 1/16th of available memory at kernel start and > add an overhead of ~20% for dynamic allocations. > diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py > index fca39968d308..4b86202b155f 100644 > --- a/scripts/gdb/linux/kasan.py > +++ b/scripts/gdb/linux/kasan.py > @@ -7,7 +7,7 @@ > # > > import gdb > -from linux import constants, mm > +from linux import constants, utils, mm > from ctypes import c_int64 as s64 > > def help(): > @@ -40,7 +40,7 @@ class KasanMemToShadow(gdb.Command): > else: > help() > def kasan_mem_to_shadow(self, addr): > - if constants.CONFIG_KASAN_SW_TAGS: > + if constants.CONFIG_KASAN_SW_TAGS and not utils.is_target_arch('= x86'): This change seems to belong to the patch that changes how the shadow memory address is calculated. > addr =3D s64(addr) > return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_op= s.KASAN_SHADOW_OFFSET > > -- > 2.50.1 >