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AJvYcCXc09Ev/hntvs0zsp0P7YRusmOBSkmme+yVCEd6sohBcNmbQfX/1pCs8nM4SUcgkH6cc7mK6OUOKQ==@kvack.org X-Gm-Message-State: AOJu0YzOieT/jbaEIy9ddRNOYleHGZdQyMOfNAwuZGVIHgLWchOJjPe3 wB1dgJ2W8CHVmgqIj55SAeux28VGJfFuubRQaN0N/F82jpnxkYfX4mMDJtpbd/umUJZBM8wTSQK nX08/7iAgrAYU/zeou4CAQtZy/ji0Z5JgyUut3Dpw X-Gm-Gg: ASbGnct8phMXjFI4xGsifupa7uCfGguEfcDWQ9pB7/Cn2JijedUG1v+c5fveBJIsm7S 1/XlNiizr0zXakYBSLKS1vX+hqjjDD0gE2n1BHTwDE5k50J5qFHG4Cbk9P9GhWSJY3HJ8fOeyZz MMWblwozcMBOaHc+PqP7tKGFjI3RDJiiY4YK+bC98iHsRFMfXwS2gmkuUcY5Vaj5YojtrTf+xtF qDHNFd/m/xfQ0LIkkkblf/Pw1z4Dp7jSJLOA6f1L/GFpTKX/j1DVo4= X-Google-Smtp-Source: AGHT+IFeMeqAy+cuIfy8BDPUr07CVnLWSx0isY1COTxmQUhbfeHhUc/gJKs+z9vTXpQo6NDvDMpWAnnnlJDkjgySN7E= X-Received: by 2002:a17:902:d2c9:b0:266:b8a2:f605 with SMTP id d9443c01a7336-2680120ed16mr333025ad.3.1758046996934; Tue, 16 Sep 2025 11:23:16 -0700 (PDT) MIME-Version: 1.0 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> In-Reply-To: <20250916140245.5894a2aa@gandalf.local.home> From: Kalesh Singh Date: Tue, 16 Sep 2025 11:23:03 -0700 X-Gm-Features: AS18NWDeydKXZzxWqGElteJppqO6QozHlpb4s_Ylp5BcEhKGMmDvVoyYUojBOGg Message-ID: Subject: Re: [PATCH v2 7/7] mm/tracing: introduce max_vma_count_exceeded trace event To: Steven Rostedt 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: uaxsbo7hkou74ngj9431y61menm4mjhp X-Rspamd-Queue-Id: C7A1D4000E X-Rspam-User: X-Rspamd-Server: rspam03 X-HE-Tag: 1758046998-432391 X-HE-Meta: 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 RkXdnz91 o4Gy0lyBg1WQ3RkYAzu//OGs/cjT1aDQWadzm9sy8K1hrYKGXSlzDvyyRNiN4XT0bTMXRDZ0WnV1elVcSVEyug75c6xVtdzFqLypAJ5XdE3HGs1/CekqqZtIjLPiCwsOQHFn0GFzWLcK+581lqIPrI5EGEEKetutW4dbEt/gwv2VXgwGesvI7sj1JZnzLhFWg36iuIxmHyIi1vw86dHsDj9B4MlfTSa7VZuqNy7T4WxmcuOSMWTO9l9awjnw1wpyKK3ZTvrWrY9BzrBXJuqjVEdN6vFUfgCab52nMwVY0RjpvbFD6M3cjLTmATXgY8cCQIJlZ 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, Sep 16, 2025 at 11:01=E2=80=AFAM Steven Rostedt wrote: > > On Tue, 16 Sep 2025 10:57:43 -0700 > Kalesh Singh wrote: > > > > BTW, why the hash of the mm pointer and not the pointer itself? We sa= ve > > > pointers in lots of places, and if it is the pointer, you could use a= n > > > eprobe to attache to the trace event to dereference its fields. > > > > In Android we try to avoid exposing raw kernel pointers to userspace > > for security reasons: raising /proc/sys/kernel/kptr_restrict to 2 > > immediately after symbols are resolved for necessary telemetry tooling > > during early boot. I believe this is also why rss_stat uses the hash > > and not the raw pointer. > > When it comes to tracing, you already lost. If it goes into the ring buff= er > 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? > > 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. Thanks, Kalesh > > -- Steve