Time stamps for the ring buffer are created by the difference between two events. Each page of the ring buffer holds a full 64 bit timestamp. Each event has a 27 bit delta stamp from the last event. The unit of time is nanoseconds, so 27 bits can hold ~134 milliseconds. If two events happen more than 134 milliseconds apart, a time extend is inserted to add more bits for the delta. The time extend has 59 bits, which is good for ~18 years. Currently the time extend is committed separately from the event. If an event is discarded before it is committed, due to filtering, the time extend still exists. If all events are being filtered, then after ~134 milliseconds a new time extend will be added to the buffer. This can only happen till the end of the page. Since each page holds a full timestamp, there is no reason to add a time extend to the beginning of a page. Time extends can only fill a page that has actual data at the beginning, so there is no fear that time extends will fill more than a page without any data. When reading an event, a loop is made to skip over time extends since they are only used to maintain the time stamp and are never given to the caller. As a paranoid check to prevent the loop running forever, with the knowledge that time extends may only fill a page, a check is made that tests the iteration of the loop, and if the iteration is more than the number of time extends that can fit in a page a warning is printed and the ring buffer is disabled (all of ftrace is also disabled with it). There is another event type that is called a TIMESTAMP which can hold 64 bits of data in the theoretical case that two events happen 18 years apart. This code has not been implemented, but the name of this event exists, as well as the structure for it. The size of a TIMESTAMP is 16 bytes, where as a time extend is only 8 bytes. The macro used to calculate how many time extends can fit on a page used the TIMESTAMP size instead of the time extend size cutting the amount in half. The following test case can easily trigger the warning since we only need to have half the page filled with time extends to trigger the warning: # cd /sys/kernel/debug/tracing/ # echo function > current_tracer # echo 'common_pid < 0' > events/ftrace/function/filter # echo > trace # echo 1 > trace_marker # sleep 120 # cat trace Enabling the function tracer and then setting the filter to only trace functions where the process id is negative (no events), then clearing the trace buffer to ensure that we have nothing in the buffer, then write to trace_marker to add an event to the beginning of a page, sleep for 2 minutes (only 35 seconds is probably needed, but this guarantees the bug), and then finally reading the trace which will trigger the bug. This patch fixes the typo and prevents the false positive of that warning. Reported-by: Hans J. Koch <hjk@linutronix.de> Tested-by: Hans J. Koch <hjk@linutronix.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Stable Kernel <stable@kernel.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: tracing: t_start: reset FTRACE_ITER_HASH in case of seek/pread perf symbols: Fix multiple initialization of symbol system perf: Fix CPU hotplug perf, trace: Fix module leak tracing/kprobe: Fix handling of C-unlike argument names tracing/kprobes: Fix handling of argument names perf probe: Fix handling of arguments names perf probe: Fix return probe support tracing/kprobe: Fix a memory leak in error case tracing: Do not allow llseek to set_ftrace_filter
Be sure to avoid entering t_show() with FTRACE_ITER_HASH set without having properly started the iterator to iterate the hash. This case is degenerate and, as discovered by Robert Swiecki, can cause t_hash_show() to misuse a pointer. This causes a NULL ptr deref with possible security implications. Tracked as CVE-2010-3079. Cc: Robert Swiecki <swiecki@google.com> Cc: Eugene Teo <eugene@redhat.com> Cc: <stable@kernel.org> Signed-off-by: Chris Wright <chrisw@sous-sol.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Commit 1c024eca (perf, trace: Optimize tracepoints by using per-tracepoint-per-cpu hlist to track events) caused a module refcount leak. Reported-And-Tested-by: Avi Kivity <avi@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <4C7E1F12.8030304@cn.fujitsu.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: gcc-4.6: kernel/*: Fix unused but set warnings mutex: Fix annotations to include it in kernel-locking docbook pid: make setpgid() system call use RCU read-side critical section MAINTAINERS: Add RCU's public git tree
Check the argument name whether it is invalid (not C-like symbol name). This makes event format simple. Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> LKML-Reference: <20100827113912.22882.62313.stgit@ltc236.sdl.hitachi.co.jp> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Set "argN" name for each argument automatically if it has no specified name. Since dynamic trace event(kprobe_events) accepts special characters for its argument, its format can show those special characters (e.g. '$', '%', '+'). However, perf can't parse those format because of the character (especially '%') mess up the format. This sets "argX" name for those arguments if user omitted the argument names. E.g. # echo 'p do_fork %ax IP=%ip $stack' > tracing/kprobe_events # cat tracing/kprobe_events p:kprobes/p_do_fork_0 do_fork arg1=%ax IP=%ip arg3=$stack Reported-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> LKML-Reference: <20100827113906.22882.59312.stgit@ltc236.sdl.hitachi.co.jp> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Fix a memory leak which happens when a field name conflicts with others. In error case, free_trace_probe() will free all arguments until nr_args, so this increments nr_args the begining of the loop instead of the end. Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> LKML-Reference: <20100827113846.22882.12670.stgit@ltc236.sdl.hitachi.co.jp> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Reading the file set_ftrace_filter does three things. 1) shows whether or not filters are set for the function tracer 2) shows what functions are set for the function tracer 3) shows what triggers are set on any functions 3 is independent from 1 and 2. The way this file currently works is that it is a state machine, and as you read it, it may change state. But this assumption breaks when you use lseek() on the file. The state machine gets out of sync and the t_show() may use the wrong pointer and cause a kernel oops. Luckily, this will only kill the app that does the lseek, but the app dies while holding a mutex. This prevents anyone else from using the set_ftrace_filter file (or any other function tracing file for that matter). A real fix for this is to rewrite the code, but that is too much for a -rc release or stable. This patch simply disables llseek on the set_ftrace_filter() file for now, and we can do the proper fix for the next major release. Reported-by: Robert Swiecki <swiecki@google.com> Cc: Chris Wright <chrisw@sous-sol.org> Cc: Tavis Ormandy <taviso@google.com> Cc: Eugene Teo <eugene@redhat.com> Cc: vendor-sec@lst.de Cc: <stable@kernel.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
No real bugs I believe, just some dead code. Signed-off-by: Andi Kleen <ak@linux.intel.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: andi@firstfloor.org Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>