user/sven/linux.git/kernel/trace/trace_uprobe.c, branch v3.18.67

perf: Avoid horrible stack usage

2017-04-30T03:49:15Z

commit 86038c5ea81b519a8a1fcfcd5e4599aab0cdd119 upstream. Both Linus (most recent) and Steve (a while ago) reported that perf related callbacks have massive stack bloat. The problem is that software events need a pt_regs in order to properly report the event location and unwind stack. And because we could not assume one was present we allocated one on stack and filled it with minimal bits required for operation. Now, pt_regs is quite large, so this is undesirable. Furthermore it turns out that most sites actually have a pt_regs pointer available, making this even more onerous, as the stack space is pointless waste. This patch addresses the problem by observing that software events have well defined nesting semantics, therefore we can use static per-cpu storage instead of on-stack. Linus made the further observation that all but the scheduler callers of perf_sw_event() have a pt_regs available, so we change the regular perf_sw_event() to require a valid pt_regs (where it used to be optional) and add perf_sw_event_sched() for the scheduler. We have a scheduler specific call instead of a more generic _noregs() like construct because we can assume non-recursion from the scheduler and thereby simplify the code further (_noregs would have to put the recursion context call inline in order to assertain which __perf_regs element to use). One last note on the implementation of perf_trace_buf_prepare(); we allow .regs = NULL for those cases where we already have a pt_regs pointer available and do not need another. Reported-by: Linus Torvalds Reported-by: Steven Rostedt Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Javi Merino Cc: Linus Torvalds Cc: Mathieu Desnoyers Cc: Oleg Nesterov Cc: Paul Mackerras Cc: Petr Mladek Cc: Steven Rostedt Cc: Tom Zanussi Cc: Vaibhav Nagarnaik Link: http://lkml.kernel.org/r/20141216115041.GW3337@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar Cc: Arnd Bergmann Signed-off-by: Greg Kroah-Hartman

tracing/uprobes: Kill the dead TRACE_EVENT_FL_USE_CALL_FILTER logic

2014-07-16T18:25:19Z

alloc_trace_uprobe() sets TRACE_EVENT_FL_USE_CALL_FILTER for unknown reason and this is simply wrong. Fortunately this has no effect because register_uprobe_event() clears call->flags after that. Kill both. This trace_uprobe was kzalloc'ed and we rely on this fact anyway. Link: http://lkml.kernel.org/p/20140715184824.GA20505@redhat.com Signed-off-by: Oleg Nesterov Acked-by: Srikar Dronamraju Signed-off-by: Steven Rostedt

tracing/uprobes: Fix the usage of uprobe_buffer_enable() in probe_event_enable()

2014-06-30T17:22:33Z

The usage of uprobe_buffer_enable() added by dcad1a20 is very wrong, 1. uprobe_buffer_enable() and uprobe_buffer_disable() are not balanced, _enable() should be called only if !enabled. 2. If uprobe_buffer_enable() fails probe_event_enable() should clear tp.flags and free event_file_link. 3. If uprobe_register() fails it should do uprobe_buffer_disable(). Link: http://lkml.kernel.org/p/20140627170146.GA18332@redhat.com Acked-by: Namhyung Kim Acked-by: Srikar Dronamraju Reviewed-by: Masami Hiramatsu Fixes: dcad1a204f72 "tracing/uprobes: Fetch args before reserving a ring buffer" Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt

tracing/uprobes: Kill the bogus UPROBE_HANDLER_REMOVE code in uprobe_dispatcher()

2014-06-30T17:22:23Z

I do not know why dd9fa555d7bb "tracing/uprobes: Move argument fetching to uprobe_dispatcher()" added the UPROBE_HANDLER_REMOVE, but it looks wrong. OK, perhaps it makes sense to avoid store_trace_args() if the tracee is nacked by uprobe_perf_filter(). But then we should kill the same code in uprobe_perf_func() and unify the TRACE/PROFILE filtering (we need to do this anyway to mix perf/ftrace). Until then this code actually adds the pessimization because uprobe_perf_filter() will be called twice and return T in likely case. Link: http://lkml.kernel.org/p/20140627170143.GA18329@redhat.com Acked-by: Namhyung Kim Acked-by: Srikar Dronamraju Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt

tracing/uprobes: Revert "Support mix of ftrace and perf"

2014-06-30T17:21:58Z

This reverts commit 43fe98913c9f67e3b523615ee3316f9520a623e0. This patch is very wrong. Firstly, this change leads to unbalanced uprobe_unregister(). Just for example, # perf probe -x /lib/libc.so.6 syscall # echo 1 >> /sys/kernel/debug/tracing/events/probe_libc/enable # perf record -e probe_libc:syscall whatever after that uprobe is dead (unregistered) but the user of ftrace/perf can't know this, and it looks as if nobody hits this probe. This would be easy to fix, but there are other reasons why it is not simple to mix ftrace and perf. If nothing else, they can't share the same ->consumer.filter. This is fixable too, but probably we need to fix the poorly designed uprobe_register() interface first. At least "register" and "apply" should be clearly separated. Link: http://lkml.kernel.org/p/20140627170136.GA18319@redhat.com Cc: Tom Zanussi Cc: "zhangwei(Jovi)" Cc: stable@vger.kernel.org # v3.14 Acked-by: Namhyung Kim Acked-by: Srikar Dronamraju Reviewed-by: Masami Hiramatsu Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt

Merge branch 'perf/kprobes' into perf/core

2014-06-05T10:26:50Z

Conflicts: arch/x86/kernel/traps.c The kprobes enhancements are fully cooked, ship them upstream. Signed-off-by: Ingo Molnar

uprobes/tracing: Fix uprobe_perf_open() on uprobe_apply() failure

2014-04-30T17:10:42Z

uprobe_perf_open()->uprobe_apply() can fail, but this error is wrongly ignored. Change uprobe_perf_open() to do uprobe_perf_close() and return the error code in this case. Change uprobe_perf_close() to propogate the error from uprobe_apply() as well, although it should not fail. Signed-off-by: Oleg Nesterov Acked-by: Steven Rostedt Acked-by: Srikar Dronamraju

uprobes/tracing: Make uprobe_perf_close() visible to uprobe_perf_open()

2014-04-30T17:10:42Z

Preparation. Move uprobe_perf_close() up before uprobe_perf_open() to avoid the forward declaration in the next patch and make it readable. Signed-off-by: Oleg Nesterov Acked-by: Steven Rostedt Acked-by: Srikar Dronamraju

kprobes, ftrace: Allow probing on some functions

2014-04-24T08:03:02Z

There is no need to prohibit probing on the functions used for preparation and uprobe only fetch functions. Those are safely probed because those are not invoked from kprobe's breakpoint/fault/debug handlers. So there is no chance to cause recursive exceptions. Following functions are now removed from the kprobes blacklist: update_bitfield_fetch_param free_bitfield_fetch_param kprobe_register FETCH_FUNC_NAME(stack, type) in trace_uprobe.c FETCH_FUNC_NAME(memory, type) in trace_uprobe.c FETCH_FUNC_NAME(memory, string) in trace_uprobe.c FETCH_FUNC_NAME(memory, string_size) in trace_uprobe.c FETCH_FUNC_NAME(file_offset, type) in trace_uprobe.c Signed-off-by: Masami Hiramatsu Cc: Frederic Weisbecker Cc: Steven Rostedt Link: http://lkml.kernel.org/r/20140417081800.26341.56504.stgit@ltc230.yrl.intra.hitachi.co.jp Signed-off-by: Ingo Molnar

tracing/uprobes: Fix uprobe_cpu_buffer memory leak

2014-04-17T14:44:42Z

Forgot to free uprobe_cpu_buffer percpu page in uprobe_buffer_disable(). Link: http://lkml.kernel.org/p/534F8B3F.1090407@huawei.com Cc: stable@vger.kernel.org # v3.14+ Acked-by: Namhyung Kim Signed-off-by: zhangwei(Jovi) Signed-off-by: Steven Rostedt