Re: [PATCH v23 3/5] tracing: Allow user-space mapping of the ring-buffer

Steven Rostedt
2024-07-02T15:18:11Z

On Tue, 2 Jul 2024 10:36:03 -0400
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:

> > 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

Ug, it's been so long, I completely forgot about that file.

Thanks for catching this.

>
> Otherwise this duplicate will confuse all system call instrumentation
> tooling.

Agreed, what if we did this then:

-- Steve

diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst
index a141e8e65c5d..9a97030c6c8d 100644
--- a/Documentation/userspace-api/ioctl/ioctl-number.rst
+++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
@@ -186,6 +186,7 @@ Code Seq# Include File Comments
'Q' all linux/soundcard.h
'R' 00-1F linux/random.h conflict!
'R' 01 linux/rfkill.h conflict!
+'R' 20-2F linux/trace_mmap.h
'R' C0-DF net/bluetooth/rfcomm.h
'R' E0 uapi/linux/fsl_mc.h
'S' all linux/cdrom.h conflict!
diff --git a/include/uapi/linux/trace_mmap.h b/include/uapi/linux/trace_mmap.h
index bd1066754220..c102ef35d11e 100644
--- a/include/uapi/linux/trace_mmap.h
+++ b/include/uapi/linux/trace_mmap.h
@@ -43,6 +43,6 @@ struct trace_buffer_meta {
__u64 Reserved2;
};

-#define TRACE_MMAP_IOCTL_GET_READER _IO('T', 0x1)
+#define TRACE_MMAP_IOCTL_GET_READER _IO('R', 0x20)

#endif /* _TRACE_MMAP_H_ */