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Levin" Cc: Vincent Donnefort , mhiramat@kernel.org, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds References: <20240510140435.3550353-1-vdonnefort@google.com> <20240510140435.3550353-4-vdonnefort@google.com> <20240630105322.GA17573@altlinux.org> <20240630084053.0b506916@rorschach.local.home> From: Mathieu Desnoyers Content-Language: en-US In-Reply-To: <20240630084053.0b506916@rorschach.local.home> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 4236610000A X-Stat-Signature: xm9qw1n7hihca8ad13nsaobzgy5hd84w X-HE-Tag: 1719930949-48194 X-HE-Meta: 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 ph/I16dn HLl4uyl1ub0VWG6ksDurXRcSLVqoVX7sMnDmfQAZIlkb+ckir8156631SLefRXWCN87K1uAEme6XLvKdg7DqUdIQ7VuTRG4ieJ0KZHoq9b7WYSdCij9zXU+kj9kpjqLDSUFy/6kBwl0Q8TlI4Y5rYdK+vXDnKeP7Yyr1MYyBKJYV25/fkDI/U8UpriIltyiNguV8XAYd8nLAFoiJzwD462elyt2mej5JY/h6zaDthNMR7sFACr6OBlM4abuHxmNqyHIs3A2M0jYoAvZYQwMAfghJSkMH0cge71ZUIn6p0/Xtk+mu9vJkY7z9ub4S6PgfuqpwsRWS4qCAdMNs= 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 2024-06-30 08:40, Steven Rostedt wrote: > On Sun, 30 Jun 2024 13:53:23 +0300 > "Dmitry V. Levin" wrote: > >> On Fri, May 10, 2024 at 03:04:32PM +0100, Vincent Donnefort wrote: >> [...] >>> diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mmap.h >>> index b682e9925539..bd1066754220 100644 >>> --- a/include/uapi/linux/trace_mmap.h >>> +++ b/include/uapi/linux/trace_mmap.h >>> @@ -43,4 +43,6 @@ struct trace_buffer_meta { >>> __u64 Reserved2; >>> }; >>> >>> +#define TRACE_MMAP_IOCTL_GET_READER _IO('T', 0x1) >>> + >> >> I'm sorry but among all the numbers this one was probably the least >> fortunate choice because it collides with TCGETS on most of architectures. > > Hmm, that is unfortunate. > >> >> For example, this is how strace output would look like when >> TRACE_MMAP_IOCTL_GET_READER support is added: >> >> $ strace -e ioctl stty >> ioctl(0, TCGETS or TRACE_MMAP_IOCTL_GET_READER, {c_iflag=ICRNL|IXON, c_oflag=NL0|CR0|TAB0|BS0|VT0|FF0|OPOST|ONLCR, c_cflag=B38400|CS8|CREAD, c_lflag=ISIG|ICANON|ECHO|ECHOE|ECHOK|IEXTEN|ECHOCTL|ECHOKE, ...}) = 0 >> >> Even though ioctl numbers are inherently not unique, TCGETS is >> a very traditional one, so it would be great if you could change >> TRACE_MMAP_IOCTL_GET_READER to avoid this collision. >> >> Given that _IO('T', 0x1) is _IOC(_IOC_NONE, 'T', 0x1, 0), >> something like _IOC(_IOC_NONE, 'T', 0x1, 0x1) should be OK. > > Well, it may not be too late to update this as it hasn't been > officially released in 6.10 yet. It's still only in the -rc and the > library doesn't rely on this yet (I've been holding off until 6.10 was > officially released before releasing the library that uses it). > > I can send a patch this week to update it. Or feel free to send a patch > yourself. You need to reserve an unused ioctl Code and Seq# range within: Documentation/userspace-api/ioctl/ioctl-number.rst Otherwise this duplicate will confuse all system call instrumentation tooling. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com