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bh=KpUppVZ8QZSoZsraIQoIJK5QdakJlsWa/Qre1zpsV2A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=N4EdRD/0ShkZ57IyNX70SdcB/Q5k0LEXw52dLQVujI+Vwslvq6V1hDq1tpeG1/aaX BAZ3BhKUpKgUUaSLG9f2Swj9DLuk3/9X8+1V4sGBWT+MZ8xj7+w4G+uyn9TryisCLu ucEf7pUjmBDQD08PtnyFBfYqcdTlbaDowEHWfCLU= Date: Tue, 26 May 2026 19:29:24 +0100 From: Catalin Marinas To: Maciej Wieczor-Retman Cc: Will Deacon , Jonathan Corbet , Shuah Khan , Andrey Ryabinin , Alexander Potapenko , Andrey Konovalov , Dmitry Vyukov , Vincenzo Frascino , Andrew Morton , Jan Kiszka , Kieran Bingham , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Samuel Holland , Maciej Wieczor-Retman , linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, workflows@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev Subject: Re: [PATCH v12 01/15] kasan: sw_tags: Use arithmetic shift for shadow computation Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Queue-Id: E3BE41A0002 X-Stat-Signature: uof6hiwmd8x8c1kdk3s854fou7ghdi9c X-Rspamd-Server: rspam06 X-HE-Tag: 1779820176-69607 X-HE-Meta: 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 2eVKn055 3I3ftg2kFVK54X948cERZuq/bzscxhWkfk99icYvvjvwbKxpODmeHvS4+mIv5zS3zA4bDmHK1SVeV5CixvFpqIaH82ytH6bwefwaH2OAaVXHipV3S+2/rwkc00RiJnT18ao7Z6DP4yexc2dRa51zkwGCaOmq+u+XaQTlqPRWgzrLI4HRZ7uCaAL4+CDXLv2q3kdCRlZl5nzX/pcYlJcTdHTeAMCL28iR5+wH85QVr7QEHtQ4dtTNrIUUhpqRIFBXL9g7ReIaf2INf2kjjuyPkXvDkbGeKHHZEE8wMna+Yglgx40XStAwnzJZOSwSalcN43KmnVeR+2GEcdFPJ7wBXkD1dKb/BCH62pYu04E5zTAcoUCaihmvz6TFWhCJXoY1Ckghlodc74pG1KawBewAxbzHJtHdVWG2qdV5OT8wN5glKu+MijJ0PhnxTQf68spGIKcS0VK/f1jFUxN+VSzTtho8xUA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 30, 2026 at 02:33:05PM +0000, Maciej Wieczor-Retman wrote: > diff --git a/Documentation/arch/arm64/kasan-offsets.sh b/Documentation/arch/arm64/kasan-offsets.sh > index 2dc5f9e18039..ce777c7c7804 100644 > --- a/Documentation/arch/arm64/kasan-offsets.sh > +++ b/Documentation/arch/arm64/kasan-offsets.sh > @@ -5,8 +5,12 @@ > > print_kasan_offset () { > printf "%02d\t" $1 > - printf "0x%08x00000000\n" $(( (0xffffffff & (-1 << ($1 - 1 - 32))) \ > - - (1 << (64 - 32 - $2)) )) > + if [[ $2 -ne 4 ]] then Nitpick: does this need a semicolon before 'then'? I can see Sashiko raised it here: https://sashiko.dev/#/patchset/cover.1774872838.git.m.wieczorretman@pm.me > + printf "0x%08x00000000\n" $(( (0xffffffff & (-1 << ($1 - 1 - 32))) \ > + - (1 << (64 - 32 - $2)) )) > + else > + printf "0x%08x00000000\n" $(( (0xffffffff & (-1 << ($1 - 1 - 32))) )) > + fi > } > > echo KASAN_SHADOW_SCALE_SHIFT = 3 [...] > diff --git a/scripts/gdb/linux/kasan.py b/scripts/gdb/linux/kasan.py > index 56730b3fde0b..4b86202b155f 100644 > --- a/scripts/gdb/linux/kasan.py > +++ b/scripts/gdb/linux/kasan.py > @@ -7,7 +7,8 @@ > # > > import gdb > -from linux import constants, mm > +from linux import constants, utils, mm > +from ctypes import c_int64 as s64 > > def help(): > t = """Usage: lx-kasan_mem_to_shadow [Hex memory addr] > @@ -39,6 +40,8 @@ class KasanMemToShadow(gdb.Command): > else: > help() > def kasan_mem_to_shadow(self, addr): > + if constants.CONFIG_KASAN_SW_TAGS and not utils.is_target_arch('x86'): Does this need to be constants.LX_CONFIG_KASAN_SW_TAGS? I don't claim I fully understand this script but the other constants.* use LX_*. > + addr = s64(addr) > return (addr >> self.p_ops.KASAN_SHADOW_SCALE_SHIFT) + self.p_ops.KASAN_SHADOW_OFFSET And, again, Sashiko mentions that the bitwise right shift here will fail after the cast to c_int64. I just tried this in python: >>> from ctypes import c_int64 as s64 >>> s64(0xffff000008eca008) >> 4 Traceback (most recent call last): File "", line 1, in s64(0xffff000008eca008) >> 4 ~~~~~~~~~~~~~~~~~~~~~~~~^^~~ TypeError: unsupported operand type(s) for >>: 'c_long' and 'int' I guess it's hidden by the wrong check on constants.CONFIG_KASAN_SW_TAGS. Otherwise I think the changes are fine. If you fix the above, feel free to add: Acked-by: Catalin Marinas