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b=HoAhORBvzI5/+QYS4SrI+EC+ImuqBKlq4+oE9Fw7dsa/je0trTKKGf+DLx9AKdxyK I3EvvDs24Lp8CV+fS+g03wMSahZUHHNcS9FrIuKJMHbfzOTlaBQT1GMhD735H+Gw21 kvIHX+WsKT3UaTS88fl1J4pkkIxkd8dzq5ZhuN5c= Date: Sat, 21 Mar 2026 17:08:41 -0700 From: Andrew Morton To: Aleksandr Nogikh Cc: bp@alien8.de, tglx@kernel.org, mingo@redhat.com, x86@kernel.org, linux-kernel@vger.kernel.org, dvyukov@google.com, kasan-dev@googlegroups.com, linux-mm@kvack.org, stable@vger.kernel.org Subject: Re: [PATCH v2] x86/kexec: Disable KCOV instrumentation after load_segments() Message-Id: <20260321170841.179ceada68dc55bb22064fda@linux-foundation.org> In-Reply-To: <20260317220319.788561-1-nogikh@google.com> References: <20260317220319.788561-1-nogikh@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 5E211140004 X-Stat-Signature: rqzdyfsr9dnwhbq9dk1qwzbaxcqtob4s X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1774138122-601644 X-HE-Meta: U2FsdGVkX1+XhRxSv2XWr6DhxyjJM84ueI92GVvEEoxJ3QLFZ0TBuew32F1Dp/oQgsSIIV9Gm4uVcKAOwV9kUuGtbt+Ub+cJYkfVbO+YgDgDO9It8MT6Ddl8T0WClHgWYKMsjRp+CZeVx/BuAsR/J4R2fWKgK6Cz+rM47hylpuDLI1JdLVy0L6cnnD/rYIv1bAlYAuftlkwP+zf2sct9BQVe5Lp1s+aL92D2qWNNYpkCAOSEkH4e/CH3bn43lUHK6uAStg5+U9Ca8NQI2nwjRdiPgNhVGJRvD0eoNKSPltQXYb8xHxOVzWo5/GMoilsxw1d7tlBlKYGGJSBtIzsohvIo0MBHdLCh7OtR4YQ223+43uG931YDbVxQPPDTaeze6fTWxafsGftWT8jDpmyvc0PfaH3LGxqOiMa6KxJ2TRXt9dRbJrp1uLMxfsVHHSGaxvEZ2vfdYrmcssrynaNAipAZ3jMl5dMWNUsYja56qm53VKzSDOIi9QpmXPbB72BTASfO927qiJd/4IcymAwzQsAY64pt4R1RSCB2h3/XoNi0Kw1alrrzT4v3kmOVMRfP/q4knccPcOWpbFk8nQaTFgz9mNslKQlLQYCF3OhAkGyrgfMxKzV6P7uQakb1rBb07sLeaQwR1bumTBTYt4Owm1L8oXU37qLKEHTPfgVZjlIpaftxHTZe39O+Jis8mxkjNs5GnjQ8bx5fd6b4KFEo/k3L7MQkdsIZcUTDVBGbCl/2kevWQbyq6wtdXGR8OjDQaWBvbcxO3bW626HPLdryHDCMFw37+n8pyt1EgeC5gSTHrZ/4mpOZF1a8Mk10pw3TovT04m4YlusJn1QZikFKrSDUo38sbQaOswetjU5Myn6T898wPVR8Y/pApmo3ufyQ6FCcFYasX6au2lweGYROWDevGfey0bsmQRH5BZZjYeu/CVSUOG57zlr8CzEx5jz5RFbRIe9qAw/j+pVcQKD O5Nm9Ifv o5DEBuYWYV4MFRFRCCem0N6Ln8vNQT286MRQ9FZe0lT6Boov++6I26e1bU0MkAvBpmeppFuYwEZsd2qBO/fRBTFSp36pIQH2sTLyiIfCJAx5Reexfvihy78OdZeLAZFUrnCQ3Fm29IIKIRby6MkC7PaqummNFd26qEEb4lsCjuTkcZLuELLKqcNoyqPzEMKstJNV4ZqJqh9XeVhiF9LBoOZpATK+BrI8M3Fi7Nbu+k+CmsvZyoRtEdbSbqXZhCwP/ube72ovPqXL31uO97nXN5+TwEVN8emvXNNG89iqBfBBh8NIeRVAMYt03lYUyPqpQ5v17HMJeX3oSrowLgwQ6j0KQeTDqLE/aVSVJdS6qjKV6yMGv0sxOHHSMlXUPuCqB32w9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 17 Mar 2026 23:03:19 +0100 Aleksandr Nogikh wrote: > The load_segments() function changes segment registers, invalidating > GS base (which KCOV relies on for per-cpu data). When CONFIG_KCOV is > enabled, any subsequent instrumented C code call (e.g. > native_gdt_invalidate()) begins crashing the kernel in an endless > loop. > > ... > > Disabling instrumentation for the individual functions would be too > fragile, so let's fix the bug by disabling KCOV instrumentation for > the entire machine_kexec_64.c and physaddr.c. If coverage-guided > fuzzing ever needs these components in the future, we should consider > other approaches. > AI review has questions: https://sashiko.dev/#/patchset/20260317220319.788561-1-nogikh@google.com