Re: [PATCH v23 3/5] tracing: Allow user-space mapping of the ring-buffer
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: 2024-07-02 15:32:36
Also in:
linux-api, linux-mm, lkml
On 2024-07-02 11:18, Steven Rostedt wrote:
quoted hunk ↗ jump to hunk
On Tue, 2 Jul 2024 10:36:03 -0400 Mathieu Desnoyers [off-list ref] wrote:quoted
quoted
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.rstUg, it's been so long, I completely forgot about that file. Thanks for catching this.quoted
Otherwise this duplicate will confuse all system call instrumentation tooling.Agreed, what if we did this then: -- Stevediff --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)
Note that user events also has this issue: the ioctl is not reserved in the ioctl-number.rst list. See include/uapi/linux/user_events.h: #define DIAG_IOC_MAGIC '*' /* Request to register a user_event */ #define DIAG_IOCSREG _IOWR(DIAG_IOC_MAGIC, 0, struct user_reg *) /* Request to delete a user_event */ #define DIAG_IOCSDEL _IOW(DIAG_IOC_MAGIC, 1, char *) /* Requests to unregister a user_event */ #define DIAG_IOCSUNREG _IOW(DIAG_IOC_MAGIC, 2, struct user_unreg*) Where '*' maps to Code 0x2A. Looking at the list I don't see any conflicts there, but we should definitely add it. If we use '*' for user events already, perhaps we'd want to consider using the same range for the ring buffer ioctls ? Arguably one is about instrumentation and the other is about ring buffer interaction (data transport), but those are both related to tracing. Thanks, Mathieu
#endif /* _TRACE_MMAP_H_ */
-- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com