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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 090WdlFnVuOA2OWfwJgOrzQAdZ3X6F2svZYADurZVdtshTGCITFk+YXn0iGgnVKLVN5n+aF/7j2VzU49xXNP+0o2qGCEr5mV4g44qqrp8/2H4OgloPv33zdzw70L3oSwfQzKg5PpquBmbtgCXLxvVMcC2kbQqi8cpfokHtpexW12XNiFaOrZY1YXKCZ40DhMoDI8jUenD7B7V/4MQApDJh0b8USPHFkfORrwgc4fXwpFt2cdtPsRY3hE66Cb+gQuqHTRoTcn+0L+D0Eh3ZiNmnXTi9mBRWnj3pUwgZrNeim1X6mzg+7ymsz8sylovrmiUULkIUjpN3x85qZBfeAiQj8kExsBJ2kKuz8D7wFLyYnBpOGqGzJ14HWXJpWXWGE2sysXKWUDLYjrtBXKeH3TKYWE8ti1QZ3AhzC2RfmaKGSu/A8fmyazM71hfy/1hvNX X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Sep 2026 17:10:39.0728 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: baede22b-df37-49ce-1526-08df18cc6d14 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: ZR1PEPF0000E45F.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: PAXPR08MB6703 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260922_101049_165345_5AD121FF X-CRM114-Status: GOOD ( 12.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 22/09/2026 11:59 am, Vladimir Murzin wrote: > Currently MTE selftests assume that they can skip (expected) MTE > faults by advancing the PC by 4 in mte_default_handler(), but this is > not generally safe, as the faults are triggered from arbitrary library > functions (e.g. memset() and memcpy()). For instance, memset() could > be implemented as simple as: > > mov x3, x0 // copy pointer > add x4, x0, x2 // calculate end > loop: > strb w1, [x3], #1 // faulting access > cmp x3, x4 > b.ne loop > ret > > which leads to an infinite loop since X3 could not be updated. > > Or, it could be having advanced implementation (FEAT_MOPS): > > mov x3, x0 // copy pointer > setp [x3]!, x2!, x1 // prologue > setm [x3]!, x2!, x1 // main > sete [x3]!, x2!, x1 // epilogue > ret > > with faulting access at prologue advancing PC to main could lead to > infinite loop due to main could be triggering unaligned access fault > which kernel fixing up by advancing PC back to prologue. > > Address this by introducing memory access helpers with predictable > behavior, allowing faults to be safely handled, and switch the MTE > selftests over to them. Tested on Pixel 8: Tested-by: Muhammad Usama Anjum Reviewed-by: Muhammad Usama Anjum > > Vladimir Murzin (2): > kselftest/arm64/mte: Introduce MTE safe memory accessors > kselftest/arm64/mte: Use MTE safe memory accessors > > .../selftests/arm64/mte/check_buffer_fill.c | 10 ++--- > .../selftests/arm64/mte/check_child_memory.c | 6 +-- > .../arm64/mte/check_hugetlb_options.c | 4 +- > .../selftests/arm64/mte/check_mmap_options.c | 10 ++--- > .../arm64/mte/check_tags_inclusion.c | 4 +- > .../selftests/arm64/mte/mte_common_util.h | 4 ++ > .../testing/selftests/arm64/mte/mte_helper.S | 44 +++++++++++++++++++ > 7 files changed, 65 insertions(+), 17 deletions(-) > -- Thanks, Usama