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cv=none; b=gFtQyhrtR+/q81nXEiMQFs1l4D0o+GR7nAjtm76LgH2xAJTI5rNBWgajE1EXMkUXs3UD8u /DhAgFfCSTkalCxFy3LJrpoBdONp937lq6Wqla5S+OTzFFsg7yL0WYgghqiGAv+Fbgy+7n cSGHXvAiMjQyS6m4mx7hyyz0UdkJlGU= Received: from omf02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 41DBCB6F0C; Tue, 16 Sep 2025 18:51:55 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf02.hostedemail.com (Postfix) with ESMTPA id 76DAA8000F; Tue, 16 Sep 2025 18:51:47 +0000 (UTC) Date: Tue, 16 Sep 2025 14:51:46 -0400 From: Steven Rostedt To: Kalesh Singh Cc: akpm@linux-foundation.org, minchan@kernel.org, lorenzo.stoakes@oracle.com, david@redhat.com, Liam.Howlett@oracle.com, rppt@kernel.org, pfalcato@suse.de, kernel-team@android.com, android-mm@google.com, Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Masami Hiramatsu , Mathieu Desnoyers , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Valentin Schneider , Jann Horn , Shuah Khan , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: Re: [PATCH v2 7/7] mm/tracing: introduce max_vma_count_exceeded trace event Message-ID: <20250916145146.046f56a8@batman.local.home> In-Reply-To: References: <20250915163838.631445-1-kaleshsingh@google.com> <20250915163838.631445-8-kaleshsingh@google.com> <20250915194158.472edea5@gandalf.local.home> <20250916115220.4a90c745@batman.local.home> <20250916134833.281e7f8b@gandalf.local.home> <20250916140245.5894a2aa@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (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-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX18AaF19e3B9PdxiVyBsClWhsh9I/89dalw= X-HE-Meta: U2FsdGVkX185Jk6EEAUV8t4XubC8/kXNROIjXRupcelR+hH3LPjbVvHzsC//ioq5oS07dWS2t7cQckl27RISrjNCA88UBb0WAorl7tjjsLJmAKwUX70maRG2rX9HPTBirBDH4VHEimIgl8f+sKXSAQQAFna9voNks/f8vy1zMr+7hWy7EAKlbbNCjd3jVgdRV30jSqdSv4iERGG1Z8w+dpwGGctTjQ9PNTMFD/16TifGmYPPyAk/4HUaqXfRy6P5otXkNPqkDkKMf59MRJxuHUt4InKNbMuwnay4dXCncAd6/+5o9+JNFiLY2MaD0GVL7y7Xz7aYj1A/e4MnaFiiQ0W5uB2CRAwb X-HE-Tag-Orig: 1758048707-555230 X-Rspamd-Queue-Id: 020761C000A X-Rspamd-Server: rspam05 X-Stat-Signature: zhgao48ed3ybtbf99jtjrd1dnjfqei54 X-Rspam-User: X-HE-Tag: 1758048717-351941 X-HE-Meta: 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 OzjJr6bR MprlA 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 Tue, 16 Sep 2025 11:23:03 -0700 Kalesh Singh wrote: > > When it comes to tracing, you already lost. If it goes into the ring buffer > > it's a raw pointer. BPF doesn't use the output of the trace event, so you > > are exposing nothing from that. It uses the proto directly. > > My understanding is that the BPF tracepoint type uses the trace event > fields from TP_STRUCT__entry(); whereas the raw tracepoint type has > access to the proto arguments. Please CMIW: Isn't what we'd be adding > to the trace buffer is the hashed mm_id value? Ah, right. Can't the BPF infrastructure protect against it? > > > > > Heck, if you enable function tracing, you are exposing every function > > address it traces via the raw data output. > > Right, security doesn't allow compiling CONFIG_FUNCTION_TRACER in > Android production kernels. Does it block all the other trace events that share pointers? Like nmi handler tracepoints, x86_fpu tracepoints, page_fault kernel tracepoint, tasklet tracepoints, cpu hot plug tracepoints, timer tracepoints, work queue tracepoints, ipi tracepoints, scheduling tracepoints, locking tracepoints, rcu tracepoints, dma tracepoints, module tracepoints, xdp tracepoints, filemap tracepoints, page map tracepoints, vmscan tracepoints, percpu tracepoints, kmem_cache tracepoints, mmap lock tracepoints, file lock tracepoints, and many more! (I got tired of looking them up). Again, are you really protecting anything if this one trace point hashes the pointer? Most other tracepoints expose this. If BPF can access a tracepoint entry struct, it can access the raw address and break KASLR. -- Steve