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04 Apr 2025 06:16:17 -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 07/14] x86: KASAN raw shadow memory PTE init Date: Fri, 4 Apr 2025 15:14:11 +0200 Message-ID: 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 In KASAN's generic mode the default value in shadow memory is zero. During initialization of shadow memory pages they are allocated and zeroed. In KASAN's tag-based mode the default tag for the arm64 architecture is 0xFE which corresponds to any memory that should not be accessed. On x86 (where tags are 4-bit wide instead of 8-bit wide) that tag is 0xE so during the initializations all the bytes in shadow memory pages should be filled with 0xE. Use memblock_alloc_try_nid_raw() instead of memblock_alloc_try_nid() to avoid zeroing out the memory so it can be set with the KASAN invalid tag. Signed-off-by: Maciej Wieczor-Retman --- Changelog v2: - Remove dense mode references, use memset() instead of kasan_poison(). arch/x86/mm/kasan_init_64.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/kasan_init_64.c b/arch/x86/mm/kasan_init_64.c index 0539efd0d216..e8a451cafc8c 100644 --- a/arch/x86/mm/kasan_init_64.c +++ b/arch/x86/mm/kasan_init_64.c @@ -34,6 +34,18 @@ static __init void *early_alloc(size_t size, int nid, bool should_panic) return ptr; } +static __init void *early_raw_alloc(size_t size, int nid, bool should_panic) +{ + void *ptr = memblock_alloc_try_nid_raw(size, size, + __pa(MAX_DMA_ADDRESS), MEMBLOCK_ALLOC_ACCESSIBLE, nid); + + if (!ptr && should_panic) + panic("%pS: Failed to allocate page, nid=%d from=%lx\n", + (void *)_RET_IP_, nid, __pa(MAX_DMA_ADDRESS)); + + return ptr; +} + static void __init kasan_populate_pmd(pmd_t *pmd, unsigned long addr, unsigned long end, int nid) { @@ -63,8 +75,9 @@ static void __init kasan_populate_pmd(pmd_t *pmd, unsigned long addr, if (!pte_none(*pte)) continue; - p = early_alloc(PAGE_SIZE, nid, true); - entry = pfn_pte(PFN_DOWN(__pa(p)), PAGE_KERNEL); + p = early_raw_alloc(PAGE_SIZE, nid, true); + memset(p, PAGE_SIZE, KASAN_SHADOW_INIT); + entry = pfn_pte(PFN_DOWN(__pa_nodebug(p)), PAGE_KERNEL); set_pte_at(&init_mm, addr, pte, entry); } while (pte++, addr += PAGE_SIZE, addr != end); } @@ -436,7 +449,7 @@ void __init kasan_init(void) * it may contain some garbage. Now we can clear and write protect it, * since after the TLB flush no one should write to it. */ - memset(kasan_early_shadow_page, 0, PAGE_SIZE); + memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE); for (i = 0; i < PTRS_PER_PTE; i++) { pte_t pte; pgprot_t prot;