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04 Apr 2025 06:18:03 -0700 From: Maciej Wieczor-Retman To: hpa@zytor.com, hch@infradead.org, nick.desaulniers+lkml@gmail.com, kuan-ying.lee@canonical.com, masahiroy@kernel.org, samuel.holland@sifive.com, mingo@redhat.com, corbet@lwn.net, ryabinin.a.a@gmail.com, guoweikang.kernel@gmail.com, jpoimboe@kernel.org, ardb@kernel.org, vincenzo.frascino@arm.com, glider@google.com, kirill.shutemov@linux.intel.com, apopple@nvidia.com, samitolvanen@google.com, maciej.wieczor-retman@intel.com, kaleshsingh@google.com, jgross@suse.com, andreyknvl@gmail.com, scott@os.amperecomputing.com, tony.luck@intel.com, dvyukov@google.com, pasha.tatashin@soleen.com, ziy@nvidia.com, broonie@kernel.org, gatlin.newhouse@gmail.com, jackmanb@google.com, wangkefeng.wang@huawei.com, thiago.bauermann@linaro.org, tglx@linutronix.de, kees@kernel.org, akpm@linux-foundation.org, jason.andryuk@amd.com, snovitoll@gmail.com, xin@zytor.com, jan.kiszka@siemens.com, bp@alien8.de, rppt@kernel.org, peterz@infradead.org, pankaj.gupta@amd.com, thuth@redhat.com, andriy.shevchenko@linux.intel.com, joel.granados@kernel.org, kbingham@kernel.org, nicolas@fjasle.eu, mark.rutland@arm.com, surenb@google.com, catalin.marinas@arm.com, morbo@google.com, justinstitt@google.com, ubizjak@gmail.com, jhubbard@nvidia.com, urezki@gmail.com, dave.hansen@linux.intel.com, bhe@redhat.com, luto@kernel.org, baohua@kernel.org, nathan@kernel.org, will@kernel.org, brgerst@gmail.com Cc: llvm@lists.linux.dev, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, x86@kernel.org Subject: [PATCH v3 14/14] x86: Make software tag-based kasan available Date: Fri, 4 Apr 2025 15:14:18 +0200 Message-ID: <3ed2c4baaf9b182c9d9716db95387ee14d98c99c.1743772053.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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. Signed-off-by: Maciej Wieczor-Retman --- 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 | 5 +++-- arch/x86/boot/compressed/misc.h | 1 + arch/x86/include/asm/kasan.h | 9 +++++++++ arch/x86/kernel/setup.c | 2 ++ arch/x86/mm/kasan_init_64.c | 2 +- lib/Kconfig.kasan | 3 ++- 7 files changed, 22 insertions(+), 6 deletions(-) diff --git a/Documentation/arch/x86/x86_64/mm.rst b/Documentation/arch/x86/x86_64/mm.rst index f2db178b353f..1e2d6b3ae231 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 | ... unused hole ffffea0000000000 | -22 TB | ffffeaffffffffff | 1 TB | virtual memory map (vmemmap_base) ffffeb0000000000 | -21 TB | ffffebffffffffff | 1 TB | ... unused hole - ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory + ffffec0000000000 | -20 TB | fffffbffffffffff | 16 TB | KASAN shadow memory (generic mode) + fffff40000000000 | -8 TB | fffffc0000000000 | 8 TB | KASAN shadow memory (software tag-based mode) __________________|____________|__________________|_________|____________________________________________________________ | | Identical 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 | ... unused hole ffd4000000000000 | -11 PB | ffd5ffffffffffff | 0.5 PB | virtual memory map (vmemmap_base) ffd6000000000000 | -10.5 PB | ffdeffffffffffff | 2.25 PB | ... unused hole - ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory + ffdf000000000000 | -8.25 PB | fffffbffffffffff | ~8 PB | KASAN shadow memory (generic mode) + ffdffc0000000000 | -6 PB | ffeffc0000000000 | 4 PB | KASAN shadow memory (software tag-based mode) __________________|____________|__________________|_________|____________________________________________________________ | | Identical layout to the 47-bit one from here on: diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 15f346f02af0..cfe1cb15950e 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -197,6 +197,7 @@ 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 @@ -402,8 +403,8 @@ config AUDIT_ARCH config KASAN_SHADOW_OFFSET hex - depends on KASAN - default 0xdffffc0000000000 + default 0xdffffc0000000000 if KASAN_GENERIC + default 0xffeffc0000000000 if KASAN_SW_TAGS config HAVE_INTEL_TXT def_bool y diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index dd8d1a85f671..f6a87e9ad200 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 212218622963..d2eedaa092d5 100644 --- a/arch/x86/include/asm/kasan.h +++ b/arch/x86/include/asm/kasan.h @@ -6,8 +6,16 @@ #include #include #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL) +#ifdef CONFIG_KASAN_SW_TAGS +#define KASAN_SHADOW_SCALE_SHIFT 4 +#else #define KASAN_SHADOW_SCALE_SHIFT 3 +#endif +#ifdef CONFIG_KASAN_SW_TAGS +#define KASAN_SHADOW_END KASAN_SHADOW_OFFSET +#define KASAN_SHADOW_START (KASAN_SHADOW_END - ((UL(1)) << (__VIRTUAL_MASK_SHIFT - KASAN_SHADOW_SCALE_SHIFT))) +#else /* * Compiler uses shadow offset assuming that addresses start * from 0. Kernel addresses don't start from 0, so shadow @@ -24,6 +32,7 @@ #define KASAN_SHADOW_END (KASAN_SHADOW_START + \ (1ULL << (__VIRTUAL_MASK_SHIFT - \ KASAN_SHADOW_SCALE_SHIFT))) +#endif #ifndef __ASSEMBLER__ #include diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index c7164a8de983..a40d66da69f4 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -1182,6 +1182,8 @@ void __init setup_arch(char **cmdline_p) kasan_init(); + kasan_init_sw_tags(); + /* * Sync back kernel address range. * diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index e8a451cafc8c..b5cf3dca6954 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -371,7 +371,7 @@ void __init kasan_init(void) * bunch of things like kernel code, modules, EFI mapping, etc. * We need to take extra steps to not overwrite them. */ - if (pgtable_l5_enabled()) { + if (pgtable_l5_enabled() && !IS_ENABLED(CONFIG_KASAN_SW_TAGS)) { void *ptr; ptr = (void *)pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_END)); 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.