101 lines
3.1 KiB
Plaintext
101 lines
3.1 KiB
Plaintext
libtracefs(3)
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=============
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NAME
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----
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tracefs_cpu_open, tracefs_cpu_close, tracefs_cpu_alloc_fd, tracefs_cpu_free_fd - Opening trace_pipe_raw data for reading
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SYNOPSIS
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--------
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[verse]
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--
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*#include <tracefs.h>*
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struct tracefs_cpu pass:[*]*tracefs_cpu_open*(struct tracefs_instance pass:[*]_instance_,
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int _cpu_, bool _nonblock_);
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void *tracefs_cpu_close*(struct tracefs_cpu pass:[*]_tcpu_);
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struct tracefs_cpu pass:[*]*tracefs_cpu_alloc_fd*(int _fd_, int _subbuf_size_, bool _nonblock_);
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void *tracefs_cpu_free_fd*(struct tracefs_cpu pass:[*]_tcpu_);
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--
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DESCRIPTION
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-----------
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This set of APIs can be used to open the raw data from the trace_pipe_raw
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files in the tracefs file system in oder to read them with the *tracefs_cpu_read*(3)
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functions.
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The *tracefs_cpu_open()* creates a descriptor that can read the tracefs
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trace_pipe_raw file for a given _cpu_ in a given _instance_. If _instance_ is
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NULL than the toplevel trace_pipe_raw file is used.
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The *tracefs_cpu_close()* closes all the file descriptors associated to the trace_pipe_raw
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opened by *tracefs_cpu_open()*.
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The *tracefs_cpu_alloc_fd()* will create a tracefs_cpu descriptor from an existing
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file descriptor _fd_. This is useful to use when connecting to a socket or pipe where
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the other end is feeding raw tracing data in the same format as the trace_pipe_raw
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file would (like in guest to host tracing). The caller is responsible for determining
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the _subbuf_size_ that will be used to break up the sub-buffers being read by the
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file descriptor. The _nonblock_ is treated the same as the same parameter in
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*tracefs_cpu_open()*.
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The *tracefs_cpu_free_fd()* is used to free the descriptor returned by *tracefs_cpu_alloc_fd()*.
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It does all the clean up that *tracefs_cpu_close()* performs, and that could also be
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used to free up the descriptor created by *tracefs_cpu_alloc_fd()* but will also close
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the file descriptor passed in. Note that *tracefs_cpu_free_fd()* should not be used
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on the descriptor returned by *tracefs_cpu_open()* as it will not close the file descriptor
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created by it.
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RETURN VALUE
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------------
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The *tracefs_cpu_open()* returns a struct tracefs_cpu descriptor that can be
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used by the other functions or NULL on error.
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The *tracefs_cpu_alloc_fd()* returns a struct tracefs_cpu descriptor that can
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be used by the *tracefs_cpu_read*(3) related functions, where the descriptor
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will be reading the passed in _fd_ file descriptor.
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EXAMPLE
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-------
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See *tracefs_cpu_read*(3) for an example.
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FILES
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-----
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[verse]
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--
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*tracefs.h*
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Header file to include in order to have access to the library APIs.
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*-ltracefs*
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Linker switch to add when building a program that uses the library.
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--
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SEE ALSO
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--------
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*libtracefs*(3),
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*libtraceevent*(3),
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*trace-cmd*(1)
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AUTHOR
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------
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[verse]
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--
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*Steven Rostedt* <rostedt@goodmis.org>
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--
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REPORTING BUGS
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--------------
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Report bugs to <linux-trace-devel@vger.kernel.org>
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LICENSE
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-------
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libtracefs is Free Software licensed under the GNU LGPL 2.1
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RESOURCES
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---------
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https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
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COPYING
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-------
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Copyright \(C) 2022 Google, Inc. Free use of this software is granted under
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the terms of the GNU Public License (GPL).
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