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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