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AJvYcCXgWL0Bxr/32uUXvVNDr+ruMAKJebhhZxf2GwdiT7h6aBhxUWLs0nebWrzBzuTkAmM5kR9ryNmviA==@kvack.org X-Gm-Message-State: AOJu0Yy91UK+VtT4vlEzqROAX5dN1pjVVFNO5la5tPDU/2hNoB8pdHUu 9Sy0vqoZmlBqR/tPDL6LZL0KlKm9FPEwIvB+WWcrTMeoXM3JOd8cmqaR3djXGhsUxlf9PRL5Gi6 38EQZvCLHx9GkzR5UzkFUeddcXQiQxy/xnn86gB0+ X-Gm-Gg: ASbGncsZyba+T4Gjv9rR91odRys4s+2nq6xz/TtJZ5lgRHwKFIb4xQ0Vb71bkJmF/TN W3LxlTMbJeL7VIPBjyRdljuvST+FmmihLSBuAhT1EvERpC8diCqM93B2XBBx7w8lO5smPHXgIuY 7QJ5Jr4gqTSJ1vvcF9Ht7kJYUjV1gv6ZAHFRRcuTyyEgx9wh7GrekG0nZx9wwdcy/5/9Mzk4Nt9 veGZ3Z+M3o/RksRb3MM6cDdUE4yayjOSUj7lKj2yfar5WT6Q5+TryhT1q5GuMgBNNRwveAZiXwV 3d5QTzhsC3ES2SAX3bSZ8O4w592juy+2Q4US X-Google-Smtp-Source: AGHT+IH+IyV5M3UDNVO30prt5PPyyx1n6sQAkg8H+r/cXESUVZ9Sxny0Upk5iwgOz2Gyh93ucwAfPrYSF2wYVT/cQJo= X-Received: by 2002:ac8:7f84:0:b0:4d3:1b4f:dda1 with SMTP id d75a77b69052e-4eda4ff2f1fmr126391511cf.61.1762852310737; Tue, 11 Nov 2025 01:11:50 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Alexander Potapenko Date: Tue, 11 Nov 2025 10:11:14 +0100 X-Gm-Features: AWmQ_bnrR-pK5Rc9D-XEScjrYr9MOeawukkWZRpWJ1yHRGagV2Ym8rHVDa4nqXc Message-ID: Subject: Re: [PATCH v6 11/18] x86/kasan: KASAN raw shadow memory PTE init To: Maciej Wieczor-Retman Cc: xin@zytor.com, peterz@infradead.org, kaleshsingh@google.com, kbingham@kernel.org, akpm@linux-foundation.org, nathan@kernel.org, ryabinin.a.a@gmail.com, dave.hansen@linux.intel.com, bp@alien8.de, morbo@google.com, jeremy.linton@arm.com, smostafa@google.com, kees@kernel.org, baohua@kernel.org, vbabka@suse.cz, justinstitt@google.com, wangkefeng.wang@huawei.com, leitao@debian.org, jan.kiszka@siemens.com, fujita.tomonori@gmail.com, hpa@zytor.com, urezki@gmail.com, ubizjak@gmail.com, ada.coupriediaz@arm.com, nick.desaulniers+lkml@gmail.com, ojeda@kernel.org, brgerst@gmail.com, elver@google.com, pankaj.gupta@amd.com, mark.rutland@arm.com, trintaeoitogc@gmail.com, jpoimboe@kernel.org, thuth@redhat.com, pasha.tatashin@soleen.com, dvyukov@google.com, jhubbard@nvidia.com, catalin.marinas@arm.com, yeoreum.yun@arm.com, mhocko@suse.com, lorenzo.stoakes@oracle.com, samuel.holland@sifive.com, vincenzo.frascino@arm.com, bigeasy@linutronix.de, surenb@google.com, ardb@kernel.org, Liam.Howlett@oracle.com, nicolas.schier@linux.dev, ziy@nvidia.com, kas@kernel.org, tglx@linutronix.de, mingo@redhat.com, broonie@kernel.org, corbet@lwn.net, andreyknvl@gmail.com, maciej.wieczor-retman@intel.com, david@redhat.com, maz@kernel.org, rppt@kernel.org, will@kernel.org, luto@kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org, linux-kbuild@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-doc@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 1295114000A X-Stat-Signature: azgwxsifkcxxn7g3wqgpz8d1d393bkdd X-Rspam-User: X-HE-Tag: 1762852311-824152 X-HE-Meta: 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 ABf5Bfux mEKcXh6rb5gjO9lj1CtAR9W/uHIGi+8VbgJYC7cJO476rGajY+nXrrvD5gumADLBiJvjGuQRlS/GpRrDm/kSQIs/2dE6MJGlvcwA7W6v+4lzzDNbxF9Rl9rZyANdB50BeCF2u/d0rZ0u4zvdmnJ9kVwyfbY8rqqxjywmovWNPNUijeyTeIJOiQ3t/zLTpZ5rRBbWE7FqsYNqe0TGp2xHMHpGNutbkUJxEivy5jF/jOop6wI/koUgI9n/TeMccetQcDX/LWeMq6bRVCNh0vW+8uMDVQ48HPHyMKU8DUgLu+NEWUz0fZHsTig6cQkBMz9mRCHHYBSNuDpOe0YaWgtzP1UpJhA== 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 Wed, Oct 29, 2025 at 9:07=E2=80=AFPM Maciej Wieczor-Retman wrote: > > From: Maciej Wieczor-Retman > > 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 it. > > 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 Reviewed-by: Alexander Potapenko