Messages in this thread | | | Date | Fri, 23 Jan 2015 10:55:25 -0500 | From | Steven Rostedt <> | Subject | [PATCH 0/5 v2] tracing: Add new file system tracefs |
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There has been complaints that tracing is tied too much to debugfs, as there are systems that would like to perform tracing, but do not mount debugfs for security reasons. That is because any subsystem may use debugfs for debugging, and these interfaces are not always tested for security.
Creating a new tracefs that the tracing directory will now be attached to allows system admins the ability to access the tracing directory without the need to mount debugfs.
Another advantage is that debugfs does not support the system calls for mkdir and rmdir. Tracing uses these system calls to create new instances for sub buffers. This was done by a hack that hijacked the dentry ops from the "instances" debugfs dentry, and replacing it with one that could work.
Instead of using this hack, tracefs can provide a proper interface to allow the tracing system to have a mkdir and rmdir feature.
To maintain backward compatibility with older tools that expect that the tracing directory is mounted with debugfs, the tracing directory is still created under debugfs and tracefs is automatically mounted there.
Finally, a new directory is created when tracefs is enabled called /sys/kernel/tracing. This will be the new location that system admins may mount tracefs if they are not using debugfs.
Changes from v1:
o Fixed all the posting problems (included files that were missing and removed changes that were not suppose to be there).
o Changed the mkdir/rmdir logic. Instead of trying to keep the inode mutexes locked, which caused locking issues with other locks that were taken, the locks are still released. But this time, they are released by the tracefs system which has a bit more control. As the mkdir/rmdir methods for the tracing facility only need the new name of the instance, the tracefs mkdir/rmdir copies the name from the dentry, releases the locks, and passes in the copy to the tracing methods.
Steven Rostedt (Red Hat) (5): tracefs: Add new tracefs file system tracing: Convert the tracing facility over to use tracefs tracing: Automatically mount tracefs on debugfs/tracing tracefs: Add directory /sys/kernel/tracing tracing: Have mkdir and rmdir be part of tracefs
---- fs/Makefile | 1 + fs/tracefs/Makefile | 4 + fs/tracefs/inode.c | 658 +++++++++++++++++++++++++++++++++++ include/linux/tracefs.h | 48 +++ include/uapi/linux/magic.h | 2 + kernel/trace/ftrace.c | 22 +- kernel/trace/trace.c | 176 +++++----- kernel/trace/trace.h | 2 +- kernel/trace/trace_events.c | 32 +- kernel/trace/trace_functions_graph.c | 7 +- kernel/trace/trace_kprobe.c | 10 +- kernel/trace/trace_probe.h | 2 +- kernel/trace/trace_stat.c | 10 +- 13 files changed, 844 insertions(+), 130 deletions(-)
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