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authorLinus Torvalds <torvalds@linux-foundation.org>2015-01-17 07:55:52 +1300
committerLinus Torvalds <torvalds@linux-foundation.org>2015-01-17 07:55:52 +1300
commit23aa4b416afdf37869e53c188944dd7c4c47949a (patch)
tree152beefdd89d3b6af0e67e623d475aaad1883cd5 /fs
parentcb59670870d90ff8bc31f5f2efc407c6fe4938c0 (diff)
parentce1039bd3a89e99e4f624e75fb1777fc92d76eb3 (diff)
Merge tag 'trace-fixes-v3.19-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull ftrace fixes from Steven Rostedt: "This holds a few fixes to the ftrace infrastructure as well as the mixture of function graph tracing and kprobes. When jprobes and function graph tracing is enabled at the same time it will crash the system: # modprobe jprobe_example # echo function_graph > /sys/kernel/debug/tracing/current_tracer After the first fork (jprobe_example probes it), the system will crash. This is due to the way jprobes copies the stack frame and does not do a normal function return. This messes up with the function graph tracing accounting which hijacks the return address from the stack and replaces it with a hook function. It saves the return addresses in a separate stack to put back the correct return address when done. But because the jprobe functions do not do a normal return, their stack addresses are not put back until the function they probe is called, which means that the probed function will get the return address of the jprobe handler instead of its own. The simple fix here was to disable function graph tracing while the jprobe handler is being called. While debugging this I found two minor bugs with the function graph tracing. The first was about the function graph tracer sharing its function hash with the function tracer (they both get filtered by the same input). The changing of the set_ftrace_filter would not sync the function recording records after a change if the function tracer was disabled but the function graph tracer was enabled. This was due to the update only checking one of the ops instead of the shared ops to see if they were enabled and should perform the sync. This caused the ftrace accounting to break and a ftrace_bug() would be triggered, disabling ftrace until a reboot. The second was that the check to update records only checked one of the filter hashes. It needs to test both the "filter" and "notrace" hashes. The "filter" hash determines what functions to trace where as the "notrace" hash determines what functions not to trace (trace all but these). Both hashes need to be passed to the update code to find out what change is being done during the update. This also broke the ftrace record accounting and triggered a ftrace_bug(). This patch set also include two more fixes that were reported separately from the kprobe issue. One was that init_ftrace_syscalls() was called twice at boot up. This is not a major bug, but that call performed a rather large kmalloc (NR_syscalls * sizeof(*syscalls_metadata)). The second call made the first one a memory leak, and wastes memory. The other fix is a regression caused by an update in the v3.19 merge window. The moving to enable events early, moved the enabling before PID 1 was created. The syscall events require setting the TIF_SYSCALL_TRACEPOINT for all tasks. But for_each_process_thread() does not include the swapper task (PID 0), and ended up being a nop. A suggested fix was to add the init_task() to have its flag set, but I didn't really want to mess with PID 0 for this minor bug. Instead I disable and re-enable events again at early_initcall() where it use to be enabled. This also handles any other event that might have its own reg function that could break at early boot up" * tag 'trace-fixes-v3.19-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Fix enabling of syscall events on the command line tracing: Remove extra call to init_ftrace_syscalls() ftrace/jprobes/x86: Fix conflict between jprobes and function graph tracing ftrace: Check both notrace and filter for old hash ftrace: Fix updating of filters for shared global_ops filters
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