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AJvYcCWY3cWnXmPEVHDM2Ovy1GqsrqtZ/6z5mokPk0OrnChcHX6PUY5BMDhXI7bLu35uFEZm4VmZn0wr9g==@kvack.org X-Gm-Message-State: AOJu0YyNGKrcHCuI51JnNRckdoZjSnpa5s9Sc5nGhIitWs1okdV/awG6 amt/+pDpWKNaT/wWBH1Nyxnm6oxg/slDba6LtTx/E253GyT7+KDRVLVFspGSKZQxuv6fIsaazaK skves4PEDR+iXJ+cId/eNgPreXYY= X-Gm-Gg: ASbGncuv+e3DtmQZ9kexEhqLDwDrG0+JCX8c+luSrbUTqKI43foG5q+J9pSfFTwjVPm dETHUfzw/X8tpOvC+3zTPp4M99K7g4eQiEwqIMvpDzAOEg/AQMLIrxviVa2ortDFevtSIhpcLIZ EgDGthFZZxbf7vvt5DBMhi7TebjNE= X-Google-Smtp-Source: AGHT+IHWPKWTHbtn0upDeL/n8bU40gn0yInHJsN/Rx11n80rZjNU/L/rCSH6qMBV6U/AqlSRsE+U9L0kwT/++6fzLW8= X-Received: by 2002:a5d:47cf:0:b0:390:f832:383f with SMTP id ffacd0b85a97d-3971d1348b7mr18713568f8f.2.1742311911851; Tue, 18 Mar 2025 08:31:51 -0700 (PDT) MIME-Version: 1.0 References: <6wdzi5lszeaycdfjjowrbsnniks35zhatavknktskslwop5fne@uv5wzotu4ri4> In-Reply-To: From: Andrey Konovalov Date: Tue, 18 Mar 2025 16:31:40 +0100 X-Gm-Features: AQ5f1JqGFWmofpIZGo_iwNyrZk8kRGYUZ2Wq3IlRJd5hdIOL8VoWslIcfmDgzvQ Message-ID: Subject: Re: [PATCH v2 01/14] kasan: sw_tags: Use arithmetic shift for shadow computation To: Maciej Wieczor-Retman Cc: Vitaly Buka , kees@kernel.org, julian.stecklina@cyberus-technology.de, kevinloughlin@google.com, peterz@infradead.org, tglx@linutronix.de, justinstitt@google.com, catalin.marinas@arm.com, wangkefeng.wang@huawei.com, bhe@redhat.com, ryabinin.a.a@gmail.com, kirill.shutemov@linux.intel.com, will@kernel.org, ardb@kernel.org, jason.andryuk@amd.com, dave.hansen@linux.intel.com, pasha.tatashin@soleen.com, guoweikang.kernel@gmail.com, dwmw@amazon.co.uk, mark.rutland@arm.com, broonie@kernel.org, apopple@nvidia.com, bp@alien8.de, rppt@kernel.org, kaleshsingh@google.com, richard.weiyang@gmail.com, luto@kernel.org, glider@google.com, pankaj.gupta@amd.com, pawan.kumar.gupta@linux.intel.com, kuan-ying.lee@canonical.com, tony.luck@intel.com, tj@kernel.org, jgross@suse.com, dvyukov@google.com, baohua@kernel.org, samuel.holland@sifive.com, dennis@kernel.org, akpm@linux-foundation.org, thomas.weissschuh@linutronix.de, surenb@google.com, kbingham@kernel.org, ankita@nvidia.com, nathan@kernel.org, ziy@nvidia.com, xin@zytor.com, rafael.j.wysocki@intel.com, andriy.shevchenko@linux.intel.com, cl@linux.com, jhubbard@nvidia.com, hpa@zytor.com, scott@os.amperecomputing.com, david@redhat.com, jan.kiszka@siemens.com, vincenzo.frascino@arm.com, corbet@lwn.net, maz@kernel.org, mingo@redhat.com, arnd@arndb.de, ytcoode@gmail.com, xur@google.com, morbo@google.com, thiago.bauermann@linaro.org, linux-doc@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, llvm@lists.linux.dev, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 220244000E X-Stat-Signature: qez97t4frchb9nh1kwkmsp7mtucsd3hs X-Rspamd-Server: rspam06 X-HE-Tag: 1742311913-672978 X-HE-Meta: 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 SgEroOTJ rYw5IDYdq6kw4mLVXeT4vCY9z9s14UmMslMP/VCcQBglLbGlgmYe+Qwb5T/0Tfa5ESsK9sb1KVozCmtrVacUGgcDlRkIrIBQEDMz6V+MLd67JrN+Bc+c9w9oCswL5ejm5SwH+jL5Scq5LUSG2KziTTP2gz+TSffDkqd9q0SQ33ys9gxu21ScRp7E9iGWKXI3ExxvnvpUBt+9mQZZDWls/u9nOmNC5f4yIHwAkhdmmAY48q2FLoT+bIKi6Ioh7Bd6P5A4v6jg1Tw+cslQv/SI/XghW7pbrCkiB+wHWgnhYM+FG3QcITut5mdTNZ5jnxwAUhb6YwYbkrNW5jeZmFNJ8ZcrH/TpK07zfWkcSWMbi0YZfVGe9P4JUoX4eEYRj+wzMF7j4z7CHjzhI49dNcPlS5gIrkJO3D3A4P6kOEPrDWfzSn5haYxLzf88+yFWBuNvCmAqOBMS2inxeZhY= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000005, 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 Thu, Mar 13, 2025 at 3:58=E2=80=AFPM Maciej Wieczor-Retman wrote: > > >So this was my brain converting things to assembly. Feel free to > >reword/clarify the comments. > > Right, I focused too much on the signed aspect. Treating everything as > overflowing sounds better, more unified. Alright! > >It could be that your checks are equivalent to mine. What I did was to > >check that the address lies outside of both contiguous regions, which > >makes the checks symmetrical and IMO easier to follow. > > I drew this out and yeah, it looks like it's the same, just grouping the = logical > expressions differently. What do you think about incorporating something = like > the following into your comment about the x86 part? : > > Given the KASAN_SHADOW_OFFSET equal 0xffeffc0000000000 > the following ranges are valid mem-to-shadow mappings: > > 0xFFFFFFFFFFFFFFFF > INVALID > 0xFFEFFBFFFFFFFFFF - kasan_mem_to_shadow(~0UL) > VALID - kasan shadow mem > VALID - non-canonical kernel virtual address > 0xFFCFFC0000000000 - kasan_mem_to_shadow(0xFEUL << 56) > INVALID > 0x07EFFBFFFFFFFFFF - kasan_mem_to_shadow(~0UL >> 1) > VALID - non-canonical user virtual addresses > VALID - user addresses > 0x07CFFC0000000000 - kasan_mem_to_shadow(0x7EUL << 56) > INVALID > 0x0000000000000000 Sounds good - I like this visual representation a lot! Thanks!